USGS Research on Energy Resources-1990 

Program and Abstracts 
Cover.-Left Hand Collet Canyon, Kaiparowits Plateau, Utah. This canyon cuts 

through Coniacian and Santonian strata. Thick coal beds at the head of the canyon 

were deposited penecontemporaneously with shoreface deposits at the mouth of 

the canyon, only 2.5 km away. Original color slide by Peter J. McCabe. 

Title page.-The John Henry Member of the Straight Cliffs Formation in Smoky 

Hollow, Kaiparowits Plateau, Utah. In this area the John Henry consists mostly of 

crevasse splay deposits that accumulated updip of extensive coal deposits, which 

accumulated in raised mires. Cliff is about 200 m high. Original color slide by 

Peter J. McCabe. 
USGS Research on Energy Resources-1990 

Program and Abstracts 

Edited by L.M.H. Carter 
DEPARTMENT OF THE INTERIOR 

MANUEL LUJAN, JR., Secretary 

U.S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director 

UNITED STATES GOVERNMENT PRINTING OFFICE: 1990 

Organizing Committee for the 1990 McKelvey Forum: 

Charles W. Holmes, Chairman 

Michael E. Brownfield 

Lorna Carter 

Anny B. Coury 

Edward Johnson 

Peter J. McCabe 

William H. Orem 

James W. Schmoker 

Christine E. Turner-Peterson 

Brenda Williams 

Library of Congress Cataloging in Publication Data 

V.E. McKelvey Forum on Mineral and Energy Resources 

(6th : 1990 : Houston, Tex.) 

USGS research on energy resources-1990. 

(U .S. Geological Survey circular; 1060) 

Supt. of Docs. no.: I 19.4/2:1060 

1. Power resources-Congresses. 

II . Geological Survey (U .S.) Ill. Title. 

T J163.15.V36 1990 553.2 

I. Carter, Lorna M. 

IV. Series. 

89-600399 

Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply 

endorsement by the U.S. Government. 

Free on application to the Books and Open-File Reports Section, 

U.S. Geological Survey, Denver Federal Center, 

Box 25425, Denver, CO 80225 
A society's wealth depends on the use it makes of raw 

materials, energy, and especially ingenuity. 

- V.E. McKelvey 

Ill 
FOREWORD 

Dallas L. Peck, Director, U.S. Geological Survey 

The extended abstracts in this volume are summaries of papers presented 

orally and as posters at the sixth annual V .E. McKelvey Forum on Mineral and 

Energy Resources, entitled "Energy Research for the 1990's-Anticipating the 

Needs of the 21st Century." The McKelvey Forum serves as an opportunity for 

communication between the USGS and the earth-science and mineral and energy 

communities by presenting the results, recent progress, and pertinent data of 

current USGS research in formal lectures and posters. The poster sessions and the 

more informal meetings during the Forum provide many opportunities for 

concerned persons to meet individually with our scientists. I hope that the 1990 

McKelvey Forum will help make our programs even more responsive to the needs 

of these communities, particularly to the fossil-energy industry, and that the 

interaction and cooperation begun here will continue to expand. 

The Forum is named for former Director Vincent E. McKelvey in 

recognition of his lifelong dedication to the study of mineral and energy resources 

as research scientist, Chief Geologist, and Director of the U.S. Geological Survey. 

The Forum is an annual event that alternates in subject matter between mineral 

and energy resources; this year the emphasis is on energy. Although the format 

and topics addressed change somewhat from year to year, the primary purpose of 

the Forum remains the same: to encourage direct communication between USGS 

scientists, the representatives of other earth -science and mineral and energy 

organizations, and interested individuals. 

Energy programs of the USGS include investigations related to oil and gas, 

coal, geothermal resources, uranium, thorium, and oil shale. Our studies 

encompass the entire National domain, including the offshore Exclusive Economic 

Zone. Presentations in this year's Forum summarize recent research in basin 

analysis, reservoir characterization, geochemistry applied to energy resources, and 

assessment of the Nation's energy resources. A growing number of citizens of this 

country are becoming increasingly aware of the importance of effective, efficient 

utilization of our Nation's energy endowment. Research results presented at this 

Forum will contribute directly to that goal, and we are excited by the opportunity 

to present them to you and to start discussions with our colleagues in industry and 

academia. 

We welcome your suggestions concerning future energy research directions 

and projects and also for improving the McKelvey Forum. 

IV 
Sixth V.E. McKelvey Forum on Mineral and Energy Resources 

Energy Research for the 1990'sAnticipating the Needs of the 21st Century 

HOUSTON, TEXAS, FEBRUARY 20-22, 1990 

PROGRAM OF LECTURES AND DISCUSSIONS 

TUESDAY, FEBRUARY 20, 1990 

4:00-7:00 p.m. 

5:00-7:00 p.m. 

Registration, Hyatt Regency Downtown 

Ice breaker - cash bar 

WEDNESDAY, FEBRUARY 21, 1990 

7:00a.m. 

8:15a.m. 

8:30 

9:00 

9:40 

10:05 

10:30 

10:55 

11:20 

11:45 

12:00 

1:00-1:40 

Registration (registration desk will be open throughout the forum) 

OPENING SESSION 

Hal Gluskoter, presiding 

Welcome and opening remarks Dallas L. Peck 

Energy research for the 1990's Gmy w: Hill 

Introduction of keynote speaker Benjamin A. Morgan 

KEYNOTE ADDRESS AlbenlV. Bally 

Break for Coffee and Posters 

TECHNICAL SESSION 1: GENERAL SESSION 

Hal Gluskoter, presiding 

Basin analysis as an exploration tool-Paradigms lost, insights gained 

Christine E. Tumer-Peterson and NeilS. Fishman 

Predictive and actual results from 2,500 wildcat wells, offshore Gulf of 

Mexico L.J. Drea• and J.H. Schuenemeyer 

Impact of drilling off Key West, Florida-Where's the beef? 

Eugene A. Shinn 

Subsidence, eustasy, and climate-Controls on coal and clastic facies 

architecture, Cretaceous of Western United States P.J. McCabe, 

R.D. Hettinger, MA. Kirschbaum, J.D. Sanchez, mzd K. W. Shanley 

New insights from GLORIA sidescan-sonar images T.R. Bruns and 

D.C. Tl-vichell (combining 1vork summarized in abstracts by Bruns 

and others and Twichell and others) 

Adjournment of Technical Session 1; lunch 

POSTER SESSION 

v 
PROGRAM OF LECTURES AND DISCUSSIONS (CONTINUED) 

1:40 p.m. 

2:05 

2:30 

2:55 

3:20 

3:45 

4:10 

4:35 

5:00 

TECHNICAL SESSION 2: APPLICATIONS OF GEOCHEMISTRY TO 

ENERGY RESOURCE STUDIES 

T.S. Ahlbrandt, presiding 

Laser Raman and luminescence spectroscopy of carbonate 

minerals-Progress toward nondestructive microprobe techniques 

for stable isotopes, trace elements, and organic matter in zoned 

cements RC. Bunuss, T.G. Ging. KR. Cercone, VA. Pedone, and 

T.S. Hayes 

Petroleum potential of Midcontinent Rift System, Iowa-Organic 

matter and porosity preserved in 1-billion-year-old rocks James 

G. Palacas, James W. Schmoker, and Raymond R Anderson 

The global methane hydrate reservoir-Impact on petroleum 

exploration Keith A. Kvenvolden and Timothy S. Collett 

Domed, rainfall-dominated peat in Indonesia as a model for lowsulfur coal Sandra G. Neuzil 

Enhanced upwelling and organic productivity during the late 

Quaternary in the northeastern Pacific Ocean Walter E. Dean and 

James V. Gardner 

Once a menace, now a burgeoning source of energy-Coal-bed 

methane in the Warrior and San Juan Basins James E. Fassett 

Controls, habitat, and resource potential of ancient bacterial gas 

Dudley D. Rice 

Global changes in climate, carbon dioxide, and organic-carbon burial 

over the last 110 million years Michael A. Anhur, Walter E. Dean, 

and David J. Allard 

Adjournment of Technical Session 2 

WEDNESDAY EVENING, FEBRUARY 21, 1990 

7:30 

8:30-10:00 p.m. 

DIRECTOR'S LECTURE: Fractal geometry, chaos theory, and their 

application in the petroleum industry Christopher C. Banon 

POSTER SESSION 

THURSDAY, FEBRUARY 22, 1990 

8:15a.m. 

8:40 

9:05 

TECHNICAL SESSION 3: RESERVOIR CHARACTERIZATION 

Donald L. Gautier, presiding 

The search for subtle traps across onshore Alaska David G. Howell 

Natural gas hydrates in the Prudhoe Bay-Kuparuk River area of 

northern Alaska Timothy S. Collett 

Characterization of hydrocarbon reservoirs in eolian sandstones C.J. 

Schenk 

VI 
PROGRAM OF LECTURES AND DISCUSSIONS (CONTINUED) 

9:30 

9:55 

10:20 

10:45 

11:10 

11:35 

12:00 

2:00p.m. 

2:25 

2:50 

3:15 

3:40 

4:05 

4:30 

Architectural studies in eolian resetvoir rocks-The Lower Jurassic 

Nugget Sandstone of northeastern Utah Fred Peterson and C.J. 

Schenk 

Break for Coffee and Posters 

Variation of modern siliciclastic turbidite systems and basin 

settings-Implications for resetvoir development C. Hans Nelson 

Application of ground-penetrating radar to development of resetvoir 

models Donald L. Gautier, C. J. Schenk, and Gary R Olhoeft 

Prediction of sandstone porosity-An extension of the concept of 

thermal maturity James W. Schmoker and Timothy C. Hester 

Adjournment of Technical Session 3 

McKELVEY FORUM LUNCHEON 

Guest Speaker: John M. Sayre, Assistant Secretary-Water and 

Science, Department of the Interior 

TECHNICAL SESSION 4: BASIN AND REGIONAL STUDIES 

Walter E. Dean, presiding 

Comparative evolution of western North America and southern 

Kazakhstan, U.S.S.R.-Two early Paleozoic carbonate passive 

margins Harry E. Cook and Michael E. Taylor 

Reassessment of tectonic history of the eastern Gulf of Mexico 

Mahlon M Ball, Ray Martin, and Richard Q. Foote 

Gulf of Mexico basin evolution-Geophysical and tectonic framework 

Kim D. Kiltgord, D. R Hutchinson, and Hans Schouten 

Deep-water fan deposits, Gulf of Mexico-Seeing through salt 

seismically Robert E. Mattick and Frederick N. Zihlman 

Rifts and hot spots-A model for the Proterozoic Midcontinent Rift 

System of North America D.R Hutchinson and RS. White 

Interplay of tectonism and sea-level change-Lessons from the U.S. 

Atlantic margin C. Wylie Poag 

Conclusion of Forum 

VII 
V. E. McKELVEY FORUM-POSTER SESSIONS 

Coal Quality 

Paleolatitude-A primary control on the sulfur content of United States coal 

Ronald H. Affolter and Gary D. Stricker 

Petrography of Permian "Gondwana" coals from boreholes in northwestern Bangladesh 

Neely Bostick, Hal Gluskoter, M. Nazrul Islam, and Q.M. Arifur Rahman 

Sulfur in coal-NCRDS applications 

M.D. Caner, SJ. Tewalt, LJ. Bragg, and RB. Finkelman 

Origin and distribution of inorganic elements in the Wyodak-Anderson coal bed, Powder River basin, 

Wyoming 

S.S. Crowley, R W. Stanton, D.M. Triplehorn, and L.F. Ruppert 

Carbon isotopic trends in peats and coals-Clues to carbon history and the environment of coal-forming 

mires 

Charles W. Holmes 

Quality parameters of Permian (Gondwana) coal, Khalaspir, Bangladesh 

E.R Landis, M.N. Islam, and Hal Gluskoter 

Data analysis and display techniques of the National Coal Resources Data System, a geologic data system 

William G. Miller, Kathleen K. Krohn, Carol L. Molnia, and Susan J. Tewalt 

Early stage diagenesis of plant biomolecules in peats 

William H. Orem and Harry E. Lerch 

Pyritic sulfur and trace-element affinities in facies of the Upper Freeport coal bed, Allegheny Formation, 

west-central Pennsylvania 

Brenda S. Pierce and Ronald W. Stanton 

Microbially mediated ftxation of uranium, sulfur, and iron in a peat-forming montane wetland, Larimer 

County, Colorado 

E./. Robbins, RA. Zielinski, J.K. Otton, D.E. Owen, R.R Schumann, and J.P. McKee 

Diagenesis of organic matter and sulfur in sapropel and peat from Mud Lake, Florida 

E.C. Spiker, P.G. Hatcher, V.J. Comer, A.L. Bates, and SA. Stout 

Liquefaction potential of facies of the Wyodak-Anderson coal bed, Powder River basin 

R W. Stanton, P.D. Warwick, and S.S. Crowley 

Is there a future for 4.0 trillion tons of low-sulfur Alaskan coal? 

Gary D. Stricker 

Depositional and diagenetic controls on the residence and isotopic composition of sulfur in Middle 

Pennsylvanian coals, southeast Iowa and northwest Illinois 

Michele L. Tuttle, Cynthia A. Rice, Joseph R Hatch, and Richard D. Harvey 

VIII 
POSTER SESSIONS (CONTINUED) 

Chemical and physical characteristics of coal beds from the Salt Range coal field, Punjab province, 

Pakistan 

P.D. WarWick, T. Shakoor, S. Javed, S.TA. Mashhad~ and M.l. Ghaznavi 

Evolution of Sedimentary Basins 

Thermal maturation in the Uinta basin, Utah 

D.E. Anders 

Subsurface studies, Santa Maria province, California 

KJ. Bird, P.H. McClellan, and T.R Bruns 

The USGS Evolution of Sedimentary Basins program 

Walter E. Dean, Samuel Y. Johnson, and Thomas D. Fouch 

Sedimentology, diagenesis, and resetvoir character of Paleogene fluvial and lacustrine rocks, Uinta 

intermontane basin, Utah-Evidence from the Altamont and Red Wash fields 

T.D. Fouch, J.K Pitman, Adam Szantay, and F. G. Ethridge 

Basin development and resultant sedimentation patterns during the transition from Sevier- to Laramidestyle tectonism, central Utah 

Karen J. Franczyk, Timothy F. Lawton, and J.K Pitman 

Geologic evolution of the Uinta-Piceance basin province, northwestern Colorado and northeastern Utah 

S. Y. Johnson, M.L. Tuttle, Bruce Bryant, RF. Dubiel, T.D. Fouch, KJ. Franczyk, V.J.S. Grauch, 

MA. Grout, RC. Johnson, C.M. Molenaar, D.J. Nichols, KM. Nichols, V.F. Nuccio, Fred 

Peterson, J.K Pitman, W.J. Perry, Jr., D. Sawatzky, RW. Scott, E.R Verbeek, and RB. Wanty 

Applications of expert systems and geographic information systems to basin characterization-Case study 

for the San Juan Basin, New Mexico 

Betty M. Miller 

Stratigraphic cross sections of Upper Cretaceous rocks across the San Juan Basin, northwestern New 

Mexico and southwestern Colorado 

Cornelius M. Molenaar and James K Baird 

Genetic lithofacies in the Dakota Sandstone, a major oil- and gas-producing formation, northern San Juan 

Basin, Colorado and New Mexico 

J.L. Ridgley 

Basin analysis study of the San Juan Basin, Colorado and New Mexico 

J.L. Ridgley and A. C. Huffman, Jr. 

Structural and basement-lithological implications of gravity and seismic-reflection data across the central 

Powder River basin from the Black Hills to the Bighorn Mountains 

S.L. Robbins and JA. Grow 

Age, facies, and depositional environments of the lower Miocene Lospe Formation, Santa Maria basin, 

central California 

Richard G. Stanley, Samuel Y. Johnson, John D. Obradovich, Michele L. Tuttle, Mary Lou Cotton 

Thornton, David R Vork, Mark V. Filewicz, Mark A. Mason, and Carl C. Swisher III 

IX 
POSTER SESSIONS (CONTINUED) 

The Point Lookout Sandstone-Changing formation architecture from strandplain to delta 

Robert S. Zech and Robyn Wright-Dunbar 

Geochemistry 

Uranium favorability in the Chadron Formation, southeastern Wyoming and northwestern Nebraska 

KA. Dickinson and P.L. Hansley 

Sulfur isotope evidence for the origin of cap-rock-hosted sulfide deposits, Hockley salt dome, Texas 

J. Richard Kyle, William N. Agee, Tim W. Johnson, and W.C. Shanks, III 

Geochemical evaluation of gas-bearing coals with respect to maturity, Upper Cretaceous Fruitland 

Formation, San Juan Basin, New Mexico and Colorado 

G.E. Michae~ B.E. Law, and D.E. Anders 

Manganese nodules and microbial ftxation of oxidized manganese in the Huntley Meadows Wetland, 

Fairfax County, Virginia 

E./. Robbins, J.P. D'Agostino, Virginia Carter, D.S. Fanning, C.J. Gamble, J. Ostwald, R.L. Van 

Hoven, and G.K. Young 

Genesis and distribution of uraninite in solution-collapse breccia pipes, northwestern Arizona 

Karen J. Wenrich, Bradley S. Van Gosen, and Hoyt B. Sutphin 

Marine Geology and the GLORIA Program 

GLORIA images from the Gulf of Alaska and British Columbia-Subduction zones, transforms, and 

channels 

T.R. Bruns, P.R. Carlson, A.J. Stevenson, M.A. Fisher, H.F. Ryall, D.M. Mann, Maxwell Dobson, 

Quentin Huggett, Lindsay Parson, and N.G.T. Fannin 

Structural segmentation in an active submarine tectonic accretionary wedge, as disclosed by GLORIA 

sidescan sonar and multichannel seismic profiling, Caribbean plate boundary north of Haiti 

William P. Dillon, James A. Austin, Kathryn M Scanlon, N. Terence Edgar, Lindsay Parson, and 

Gordon E. Ness 

Sedimentary patterns on the mid-Atlantic continental rise as discerned by a GLORIA sidescan survey 

JohnS. Schlee and James M Robb 

A structural and stratigraphic transect across the Florida platform from the deep Gulf of Mexico to the 

deep Atlantic 

B. Ann Swift, William P. Dillon, Myung W. Lee, and Mahlon M Ball 

Depositional processes revealed by GLORIA sidescan sonar images on the Mississippi fan 

David C. Twichel~ Neil H. Kenyon, and Bonnie A. McGregor 

Reservoir Characterization and Petroleum Research 

Evidence for a geologically rapid increase and stabilization of vitrinite reflectance in response to a 

short-term temperature increase, Cerro Prieto geothermal system, Mexico 

Charles E. Barker 

X 
POSTER SESSIONS (CONTINUED) 

Stabilization of kerogen thermal maturation-Evidence from geothermometry and burial history 

reconstruction, Niobrara Limestone, Berthoud oil field, western Denver basin, Colorado 

Charles E. Barker and Bonnie L. Crysdale 

A fluid-inclusion technique for determining peak temperature and its application to establish a refined 

calibration for the vitrinite reflectance geothermometer 

Charles E. Barker and Robert H. Goldstein 

Subsurface exploration with the aid of borehole gravimetry 

Lany A. Beyer 

Cretaceous and Tertiary Sagavanirktok Formation in the Prudhoe Bay-Kuparuk River area, northern 

Alaska 

Timothy S. Collett and Kenneth J. Bird 

New information on the Nuwok Member of Sagavanirktok Formation; implications for petroleum geology 

of the North Slope and Beaufort Sea-Evidence from Carter Creek, Arctic National Wildlife Refuge 

(ANWR), Alaska · 

T.D. Fouch, E.M Brouwers, D.H. McNei~ Louie Marincovich, Jr., KJ. Bird, and H. Rieck 

A seismic reflection study of Miocene listric faulting north of Lake Mead, Nevada 

JA. Grow, RG. Bohannon, J.J. Miller, andRE. Anderson 

Effects of basin evolution on source-rock characteristics of the Woodford Shale, Anadarko basin, 

Oklahoma 

Timothy C. Hester, James W. Schmoker, and Howard L. Sahl 

Reservoir characteristics of the Lower Cretaceous J sandstone in the Kachina field, Denver basin, 

Colorado 

Debra K. Higley 

Computer display of petroleum exploration through time in the Denver basin of Colorado, Nebraska, and 

Wyoming 

Debra K. Higley and Kenneth/. Takahashi 

Petroleum geology studies in the Santa Maria province, California 

Caroline M Isaacs, J. David King, Richard M Pollastro, and Colin F. Williams 

Diagenesis of sandstones in the Norphlet Formation (Upper Jurassic), Escambia County, Alabama 

C. W. Keighin and C.J. Schenk 

Thermal evolution of the Upper Cretaceous Fruitland Formation, San Juan Basin, Colorado and New 

Mexico 

BenE. Law 

Identified petroleum systems within the United States-A 1990 status report 

Leslie B. Magoon 

Preliminary reinterpretation of the Ouachita frontal zone near Hartshorne, Oklahoma, based chiefly on 

seismic reflection data 

W.J. Peny, Jr., Warren Agena, and N.H. Suneson 

XI 
POSTER SESSIONS (CONTINUED) 

Algal mound carbonate resetvoir, Aneth oil field, Paradox basin, Utah-Origin and related petroleum 

geology 

James A. Peterson 

Western tight gas resetvoirs-Resource potential and development constraints 

Charles W. Spencer, Ben E. Law, and Ronald C. Johnson 

Resource Assessment 

Play analysis methodologies for petroleum resource assessment 

Robert A. Crovelli and Richard H. Balay 

Deep oil and gas wells and resetvoirs in the United States from the Well History Control System and 

Petroleum Data System 

T.S. Dyman, D.T. Nielsen, RC. Obuch, J.K Baird, and RA. Wzse 

New methodologies for assessment of U.S. oil-shale resources 

John R. Dyni 

New developments in uranium endowment assessment in the United States 

WaiTen I. Finch, Charles T. Pierson, Richard B. McCammon, James K Otton, Hoyt B. Sutphin, and 

Karen J. Wenrich 

Coal Resources and Their Sedimentological Setting 

Coal availability studies-A progress report 

M. Devereux Carter, Nancy K Gardner, Richard E. Sergeant, Elizabeth V.M. Campbell, and Nick 

Fedorko, III 

Architecture of clastic facies and location of coals associated with a major marine transgression-The 

mid-Cretaceous of the Kaiparowits Plateau, Utah 

Robert D. Hettinger and Peter J. McCabe 

Alluvial sandstone geometries and their relationship to coal deposition in a transgressive systems tract, 

Dakota Formation, Utah 

Mark A. Kirschbaum and Peter J. McCabe 

Characteristics of coal-bearing strata in Tertiary basins, based on integrated sedimentary and structural 

field studies, southwestern Montana 

J. W. M'Gonigle, M.H. Hait, Jr., and W.J. Perry, Jr. 

New tonstein beds in the Middle Pennsylvanian of the central Appalachian basin-Time lines for basin 

analysis 

W.F. Outerbridge, P.C. Lyons, and D.M. Triplehorn 

Variations in facies architecture related to sequence stratigraphy of the Turonian-Campanian strata, 

Kaiparowits Plateau, south-central Utah 

Keith W. Shanley and Peter J. McCabe 

Coal resources in Sind province, Pakistan 

Roger E. Thomas, Mohammed Riaz Khan, and Shafique Ahmed Khan 

XII 
Sixth V. E. McKelvey Forum on Mineral and Energy Resources 

USGS Research on Energy Resources-1990 

Program and Abstracts 

Edited by L. M. H. Carter 

Paleolatitude-A Primary Control on the 

Sulfur Content of United States Coal 

Ronald H. Affolter and Gary D. Stricker 

Previous studies on sulfur in coal have stressed the 

importance of depositional environments in controlling 

sulfur content. For example, peats overlain by marine to 

brackish-water sediments often have high sulfur 

contents, whereas fresh-water peats are low in sulfur. 

Isotope studies have shown that microorganisms play a 

direct role in concentrating sulfur in humic substances 

and that most sulfur in coal is incorporated during the 

early development of the peat. Sulfur enters the peat 

environment as sulfate and is reduced by the action of 

sulfate-reducing bacteria. The rate of sulfate reduction 

by bacteria, however, is strongly dependent on 

temperature and seasonal variations. Rates of sulfate 

reduction are generally inhibited by lowering the 

temperature about 5-10 °C. Although other factors do 

influence the sulfur content of peats, we suggest that one 

primary control is the activity of the sulfate-reducing 

bacteria in peat, and that the latitude of formation of the 

peat swamp affects this activity. 

Solar radiation striking the Earth at higher 

latitudes traverses greater distances and through a 

greater mass of atmosphere than at lower latitudes. This 

radiation at higher latitudes is also depleted by 

absorption, reflection, and scattering. Because of these 

factors, there is a surplus of solar energy between lat oo 

and 38° (more incoming energy than outgoing)and a 

deficit between lat 38° and 90° (more outgoing energy 

than incoming). Assuming that the pattern of incident 

solar radiation has remained relatively constant through 

time, then the mean incident solar radiation averaged 

Manuscript approved for publication December 15, 1989. 

over a year can be calculated. Our calculations show that 

Interior and Appalachian Carboniferous peat swamps 

received approximately 845 cal cm-2 day- 1

, Rocky 

Mountain province Cretaceous peat swamps 600 cal 

cm-2 day- 1

, Northern Great Plains Tertiary peat swamps 

550 cal cm-2 day-1 and Gulf Coast Tertiary peat swamps 

660 cal cm-2 day-1

• Alaska Tertiary peat swamps received 

380 cal cm-2 day-1 and Alaska Cretaceous peat swamps 

365 cal cm-2 day-1 • 

Our hypothesis that latitude and thereby solar 

radiation influence sulfur in peat is supported by an 

evaluation of more than 8,000 United States coals. Most 

Interior and Appalachian Carboniferous peats 

accumulated at latitudes between 0° and 15° S., Rocky 

Mountain province Cretaceous peats between 30° and 

45° N., Northern Great Plains Tertiary peats between 40° 

and 55° N., and Gulf Coast Tertiary peats between 30° 

and 40° N. Alaskan Cretaceous and Tertiary peats 

accumulated at latitudes above 70° N. A comparison of 

paleolatitudes calculated from paleomagnetic poles and 

sulfur contents indicates that the higher the latitude in 

which a peat swamp developed, the lower the mean 

sulfur content of the subsequent coal (correlation 

coefficient -0.45; significant at the 99 percent confidence 

level). Mean sulfur contents are 2.34 percent (n = 5,497, 

range=0.1 to 19.2 percent, std. dev.=1.92) in lowlatitude Carboniferous coal; 0.86 percent (n = 2,754, 

range= 0.02 to 18.9 percent, std. dev. = 0.97) for middlelatitude Cretaceous and Tertiary coals; and 0.32 percent 

(n = 262, range= 0.01 to 6.6 percent, std. dev. = 0.48) in 

high-latitude Alaskan Cretaceous and Tertiary coal. 

The latitude of peat formation determines the 

amount of incident solar radiation (energy) available to 

the system. At high latitudes lower temperatures result in 

lower rates of sulfate reduction, whereas at low latitudes 

higher temperatures result in higher rates of sulfate 

reduction. Therefore, in general, lower sulfur coals 

formed at high latitudes and higher sulfur coals formed 

at lower latitudes. 
Thermal Maturation in the 

Uinta Basin, Utah 

D.E. Anders 

The Uinta basin (24,000 km2

) in northeastern 

Utah contains abundant energy resources including oil, 

natural gas, tar sands, coal, gilsonite, and oil shale. The 

principal source of the oil, tar sands, and gilsonite is the 

kerogenous/bitumen-rich sedimentary rocks of the 

Green River Formation deposited in late Paleocene to 

late Eocene age lacustrine systems. Based on classical 

chemical maturity parameters (n-alkane distribution and 

carbon preference indices, hydrocarbon/-

non-hydrocarbon, API gravity, triaromatic/-

(triaromatic + monoaromatic) steroid ratios, 22S/22R 

bishomohopane and 20S/20R-5a,14a,17a ethylcholestane ), these energy resources were derived from source 

rocks covering a wide range of thermal maturities. In 

addition to hydrocarbons derived from thermally mature 

source rocks, numerous oil, tar sand, and gilsonite 

deposits have chemical properties characteristic of 

organic matter derived from immature source rocks. 

That these immature hydrocarbon deposits are 

widespread suggests that we have had a limited prior 

understanding of hydrocarbon generation within Green 

River source rocks. 

In an effort to better understand the thermal 

histories of hydrocarbon generation in the Uinta basin, 

we investigated the level of thermal maturity at which 

Green River Type I kerogen produces liquid 

hydrocarbons, using vitrinite reflectance (percent), Rock 

Eval (T max) and transformation ratio, atomic H/C ratio, 

hydrocarbon yield, time-temperature indices (TTl), 

subsurface temperature, and biological marker isomerization, degradation, and aromatization ratios. 

Mean random vitrinite reflectance (Rm) values for 

surface rocks of the Uinta, Duchesne River, and Browns 

Park Formations in the north half of the basin range from 

0.3 to 0.5 percent. Rm values for surface rocks of the 

Green River and Wasatch Formations in the south half of 

the basin range from 0.5 to 0.7 percent. Surface 

exposures of Cretaceous coals along the southern margin 

of the basin have Rm values in the range 0.6-0.7 percent. 

Reflectance values for subsurface rocks of approximately 

equal age and depth are variable throughout the basin. 

For example, at the 3,060 m depth, Rm values for Eocene 

rocks range from 0.4-0.5 percent at Starr Flats, to 0.7-0.8 

percent at Red Wash, to 0.8-0.9 percent at Altamont, to 

0.9-1.0 percent at South Ouray, to 1.0-1.1 percent at 

Natural Buttes. These variations reflect differences in 

geothermal gradient, maximum depth of burial, 

hydrologic cooling, and heat transfer across the basin. 

Generally, for a given stratigraphic unit, Rm values 

2 

increase southward due to higher geothermal gradients, 

but also increase northward due to increased depth of 

burial. 

Atomic H/C ratios for Type I kerogen are linearly 

related to Rm values in the stage of catagenesis (0.5 to 1.3 

percent). Hydrogen/carbon ratios for Type I kerogens of 

the Uinta basin decline from a high of 1.4 at a Rm 

equivalence of 0.5 percent to a low of 0.65 at a Rm 

equivalence of 1.3 percent. 

Rock-Eval temperature indices (Tmax) show a 

greater increase (390 to 445 °C) in the early stages of 

thermal evolution (0.3 to 0.5 percent Rm) of Green River 

kerogen, but a lesser increase ( 445 to 455 °C) in the 

catagenesis stage (0.5 to 1.4 percent, Ro ). Rock-Eval 

transformation ratios (T.R.) show little change until the 

main stage of catagenesis (oil window). Around 0.6 to 0.7 

percent Rm, the T.R.'s begin to increase from average 

values of 0.1 to a maximum of 0.6 in the 1.1 to 1.3 percent 

Rm range. 

Hydrocarbon yield as a function of Rm shows the 

main stage of liquid hydrocarbon generation is in the 0.7 

to 1.2 percent Rm range with abundant liquid 

hydrocarbons preserved to at least 1.4 percent Rm. 

The thermal gradients of the Uinta basin are locally 

variable, but systematically trend from higher values in 

the south (2.2 °F/100 ft; 39 °C/km) to lower values in the 

north (0.6 °F/100 ft; 11 °C/km). This systematic change 

parallels a thickening of less thermally conductive marls, 

shales, and conglomerate northward. Cooling in the 

north may result from downward movement of meteoric 

waters along faults and fractures associated with the 

Uinta Mountain front and (or) heat transfer from the less 

conductive sedimentary rocks to the more conductive 

quartzite-rich rocks of the Uinta Mountains. 

Based on current thermal gradients and the level of 

thermal maturity necessary to bring about catagenesis of 

Green River kerogen, maximum depths of burial and 

temperatures at the beginning and end of oil generation 

were predicted for five basin wells using the Waples TTl 

model. The TTl model indicates oil production from 

Green River Type I kerogen begins at about 100 °C, 

maximizes at 115 oc and ends between 135 and 140 oc, 

with preservation of hydrocarbons continuing to at least 

145-150 °C. Rm values corresponding to the beginning, 

peak, and end of oil generation are: 0.7, 0.9, and 1.2 

percent Rm, respectively. 

Extraction ratios (EOM/TOC) in thermally 

immature ( < 0.6 percent Rm) Green River Formation 

shale were found to average 22.5 percent. Tuffs, microfractures, and sandstone contiguous to these immature 

shales were often filled with immature hydrocarbons. 

This indication of migration of immature hydrocarbons 

can be coupled with the presence of biomarker ratios 

indicative of hydrocarbons derived from rocks with 

reflectance values < 0.6 percent Rm (in the giant tar sand 
deposits of Asphalt Ridge, P.R. Springs and Raven 

Ridge, the large gilsonite deposits of the East Central 

basin, and a significant number of shallow oils) to present 

convincing evidence of migration of large quantities of 

thermally immature hydrocarbons in the Uinta basin. 

Glob a I Changes in Climate, Carbon 

Dioxide, and Organic-Carbon 

Burial over the Last 110 Million Years 

Michael A. Arthur, Walter E. Dean, and 

David J. Allard 

Available paleoclimate data support the existence 

of a warm, equable global climate during the middle to 

Late Cretaceous, a climate which deteriorated in a series 

of steps toward the glacial late Neogene and Quaternary. 

Climate-model studies suggest that the concentration of 

C02 (carbon dioxide) in the atmosphere was 4 to 18 

times higher during the Cretaceous than today, and this 

would have been an important climatic forcing factor. 

The most likely cause of variation in C02 was change in 

the balance between the rate of tectonic C02 outgassing 

and C02 consumption resulting from organic-carbon 

burial. We have no straightforward, independent 

evidence for the magnitude of possible C02 changes, but 

two indirect lines of evidence provide some indication of 

the amount of C02 variation. (1) Variations through 

time in CCD (carbonate compensation depth) in the 

ocean and in the carbon-isotope gradient between 

surface- and deep-water masses (as measured by the 

difference in isotopic composition of calcareous 

planktonic and benthic organisms) indicate that dissolved 

C02 in the ocean decreased by as much as a factor of 5 

from the Late Cretaceous to the Holocene. (2) The 

carbon-isotopic composition of marine organic matter 

(amorphous kerogen) changed substantially over the 

same time interval and may be a C02 "paleobarometer ." 

Experimental data and geologic evidence suggest that, in 

the past, a higher concentration of dissolved C02 may 

have led to greater carbon-isotope fractionation relative 

to the carbon source and to isotopically lighter fixed 

carbon in Cretaceous marine organic matter in 

comparison to that at present. 

The photosynthetic fractionation of carbon 

isotopes in the ocean is taken as the difference between 

the 13C/2

C ratio of bulk organic matter and that of 

carbonate carbon, the latter being a monitor of the 

carbon-isotopic composition of dissolved inorganic 

carbon. This fractionation has varied significantly over 

the last 110 million years. The o 13C of most Cretaceous 

marine organic matter is -27%o or lighter, in contrast to 

that of Neogene and Quaternary organic matter, which 

3 

averages about -22%o or heavier. The o

13C of 

terrestrial higher plant material has remained 

approximately constant at about -25%o over the last 110 

m.y. The o 13C of Cretaceous marine organic carbon was 

not always as low as -27%o , however: at least one major 

positive excursion in organic carbon o 13 C to values as 

high as -21 %o took place at the Cenomanianrruronian 

boundary (Crr; =91 Ma). This isotopic excursion is 

coincident with a major inferred high-productivity 

episode that lasted less than 1 m.y. and resulted in 

significantly increased rates of organic-carbon burial. 

The err carbon-burial event apparently drew down 

atmospheric C02 and may have resulted in global 

climatic cooling, as suggested by the oxygen isotopic 

composition of inoceramid mollusks from England and 

northwest Germany. After the err event, the o 13C of 

marine organic matter decreased and the climate 

warmed again in the Late Cretaceous, followed by 

relatively minor variations of 1-2%o through the Paleogene. One of the most significant changes in the isotopic 

composition of marine organic matter occurred in the 

early middle Miocene, coincident with major global 

cooling and Southern Hemisphere glaciation. It is likely 

that a sharp drop in C02 occurred in conjunction with a 

widespread increase in the rate of burial of organic 

matter in circum-Pacific upwelling zones (the so-called 

"Monterey hypothesis"), but it is not clear whether the 

C02 drop was the cause of global cooling. 

Further information on changes with time of the 

isotopic composition of marine organic matter compared 

with that of pelagic carbonate will provide important 

constraints on compositional changes of the oceanatmosphere system, evolution of the global climate 

system, and partitioning of carbon between crustal, 

sediment, and oceanic reservoirs. 

Reassessment of Tectonic History of the 

Eastern Gulf of Mexico 

Mahlon M. Ball, Ray Martin, and 

Richard Q. Foote 

Our initial working hypothesis regarding the 

regional structural geology of the eastern Gulf of Mexico 

envisioned a set of northwest-trending fracture zones 

extending into the gulf across the Florida-Bahamas 

carbonate province. These faults were believed to have 

acted as transforms accommodating the opening of the 

Gulf of Mexico contemporaneously with initial spreading 

of the North Atlantic during the Late Jurassic. Working 

primarily with gravity and magnetic data, Kim Klitgord 

and others have proposed that blocks of pre-Mesozoic 

crust within the transform zones were separated by local 

zones of extension underlain by rifted thin transitional 
crust or Jurassic oceanic crust. Reflection seismic data 

and subsurface control further constrain this 

interpretation. Paleozoic sedimentary rocks under lie the 

Western Florida Shelf north of lat 26° N. It follows that 

this region is not underlain by Jurassic oceanic crust. The 

crust north of lat 26° N. is essentially continental. 

The deepest horizon that can be mapped seismically beneath the Western Florida Shelf is a major 

composite unconformity. The youngest known Paleozoic 

sedimentary rocks beneath this unconformity are Devonian. To the north in the Apalachicola basin and on the 

northern flank of the Middleground arch, rifting 

associated with the Mesozoic opening of the Atlantic and 

Gulf of Mexico formed half grabens that filled with 

Triassic red beds. These fills were deposited at least in 

part during rifting and erosion on adjacent highs. Erosion 

continued after cessation of graben formation with the 

result that Triassic block-faulted terrain was reduced to a 

peneplain. Subsequent onlap by Jurassic sediments and 

evaporites formed the angular unconformity revealed so 

clearly above infilled rifts in the reflection seismic lines 

crossing the Apalachicola basin. This relationship has 

resulted in identification of this erosion surface as the 

"post-rift unconformity" or "pre-Cretaceous" post-rift 

unconformity. To the south, on the Middleground arch, 

folding of Paleozoic rocks beneath the unconformity may 

be related to late Paleozoic compressional tectonism 

associated with the Carboniferous and Permian closing 

of the proto-Atlantic. Erosion on this regional unconformity may have begun in some places as early as the late 

Paleozoic and continued on the Peninsular arch of 

onshore Florida until the earliest Late Cretaceous. Most 

of the names applied to this unconformity have tended to 

obscure the extent of its composite nature. 

The northwest-trending fault zones crossing South 

Florida and the Western Florida Shelf became active in 

the Late Jurassic and continued into the Early 

Cretaceous during the opening of the Gulf of Mexico. 

There are two schools of thought concerning these fault 

zones. Some believe them to be transforms with 

predominantly strike-slip offsets. Others question the 

sense of motion on these faults. The Bahamas fracture 

zone of Klitgord and others, more recently referred to as 

the Florida lineament of Christenson, is of particular 

interest. This feature appears to continue northwestward 

into the Gilbertown-Pickens-Pollard portion of the 

circum-Gulf fault system. This fault has normal 

displacement down to the south and west on the north 

and east flanks of Destin dome in the Apalachicola basin. 

The Middle and Upper Jurassic Louann Salt thins 

abruptly to the north and east across this fault. Toward 

the southeast, along the north margin of the South 

Florida basin, gravity data have been interpreted to 

indicate coincidence of this fault zone with a "hinge 

zone" and local relief on the Mohorovicic discontinuity. 

4 

This interpretation reflects the use of erroneously low 

densities for the sedimentary fill of the South Florida 

basin. 

Salt tectonism is inferred to have begun as early as 

Late Jurassic in the Apalachicola basin. The inferred salt 

swell forming the Destin dome began later in latest Early 

Cretaceous time and continued into the Cenozoic. Late 

faulting cutting to the sea floor on the crest of Destin 

dome may provide chimneys for escape of natural gas. 

Evidence for a Geologically Rapid 

Increase and Stabilization of Vitrinite 

Reflectance in Response to a Short-Term 

Temperature Increase, Cerro Prieto 

Geothermal System, Mexico 

Charles E. Barker 

A short-term pulse of hot water affected rocks 

below 1,300 min well M-94 (fig. 1, facing), Cerro Prieto 

geothermal system, and sharply increased the vitrinite 

reflectance (thermal maturity) of sedimentary organicmatter. A 1981 study of apatite fission-track annealing by 

S.J. Sanford indicates that this hot-water pulse passed 

through these rocks in about 101 yr. The paleotemperature rapidly changed from about 75-125 °C, the present 

measurement above 1,300 m depth, to a peak paleotemperature of 250--300 °C below 1,300 m in the 

hydrothermally-altered sedimentary rocks. Present 

(equilibrium log) temperature below 1,300 m has 

declined to 150--210 °C. The peak paleotemperature is 

estimated from the homogenization of reequilibrated 

fluid inclusions in calcite, and the calcite-water oxygenisotope geothermometer, as discussed in 1981 papers by 

Barker and W.A. Elders, and S.J. Sanford, and a 1985 

paper by S.M. Sterner. Clay mineralogy also changes 

sharply below 1,300 m, as indicated by the disappearance 

of smectite+ kaolinite and the concomitant appearance 

of illite+ chlorite; but these reactions indicate a paleotemperature of only 150-180 °C, as determined in a 

1980 study by W.A. Elders and others. This discrepancy 

is possibly caused by slowness of metamorphic reactions 

in minerals. 

Vitrinite reflectance of sedimentary organic-matter 

below 1,300 m increased to a level that is consistent with 

the other peak geothermometers. The correspondence of 

peak recording geothermometers with the vitrinite 

reflectance geothermometer suggests that sedimentary 

organic-matter reacts quickly to temperature increases of 

50--100 oc above ambient even when that increase existed 

for only a short time-about 101 yr. 
APPARENT AGE, IN MILLIONS OF YEARS 

0 100 200 300 0~----------~----------~----------~ 

• 

• 

• 

0.5 

6 

6 

6 

6 

6 1.0 6 

6 

6 

6 

6 

1292m 6 

6 

1.5 

2.0 

2.5 

0 

• 

• 

• 

6. 

• 

• 

• 

• 

~ 

• 

• 

0 

100 

eo 

0 

EXPLANATION 

e TbLogT-11 

.A. Th 

6. Tvr 

0 T,so 

1----*---l F-T age 

• 

0 • 6. 

• 6 ... 6. 

• 6. 

6 

• 0 "t, 

6 

• 6 

6. • 6. 

• 6 

• 

• 

\ 6 

• 6. 

.. 6. 

06. 

6. 

0 6. 

200 300 

TEMPERATURE, IN DEGREES CELSIUS 

Figure 1 (Barker). Comparison of borehole temperature (f b) data and other geothermometers in borehole M-94, Cerro Prieto system. Fission-track apatite 

age (F-T), fluid inclusion (f h), and oxygen isotope (fi) 

data are from 1981 study by S.J. Sanford. Mineral data 

are from 1978 report of W.A. Elders and others. Vitrinite 

reflectance data are from 1981 report by Barker and 

Elders. F-T dates are plotted with ± one standard 

deviation error bars. 

5 

Stabilization of Kerogen Thermal 

Maturation-Evidence from 

Geothermometry and Burial History 

Reconstruction, Niobrara Limestone, 

Berthoud Oil Field, Western Denver 

Basin, Colorado 

Charles E. Barker and Bonnie L. Crysdale 

The burial history of a fractured Niobrara 

Limestone reservoir and source rock (fig. 1, overleaf) 

offers a unique setting for studying the stabilization of 

thermal maturity, because soon after peak temperature 

of about 100 oc was reached, exhumation lowered 

temperature to about 60-70 °C. Vitrinite reflectance 

(Rm = 0.6-0.7 percent) and published clay mineralogy 

data from the Niobrara Limestone indicate that peak 

paleotemperature was approximately 100 °C. Fluidinclusion data also indicate that oil migration occurred at 

100 °C. Burial history reconstruction indicates that 100 

°C was reached in the Niobrara Limestone only during 

maximum burial, which occurred at 70 Ma and 8,000 ft 

depth. However, erosion beginning at 70 Ma and 

continuing until 50 Ma removed more thari 3,000 ft of 

rock. This depth of erosion agrees with an Rm of 0.4 

percent measured in surface samples of the Pierre Shale 

above the field. The exhumation of the reservoir 

decreased temperature by about 30 oc to near the 

present-day bottom-hole temperature of 50-70 °C. Lopatin TTl analysis suggests that the Niobrara Limestone as 

a source rock matured to the oil-generation stage 

(TTl= 10) about 25 Ma, significantly later than 

maximum burial, and after exhumation caused cooling. 

The Lopatin TTl method in this case seems to 

overestimate the influence of heating time. If time is an 

important factor, thermal maturity should continue to 

increase after deepest burial and peak temperature, so 

that vitrinite reflectance will not be comparable to peak 

paleotemperatures estimated from geothermometers set 

at near-peak temperature and those estimated from 

burial history reconstruction. The good agreement 

between geothermometry and the burial history 

reconstruction in Berthoud State 4 suggests that the 

influence of heating time is negligible in kerogen thermal 

maturation. We infer from this conclusion that kerogen 

thermal maturation stabilizes after a geologically small 

reaction-time at peak burial temperature. 
0 10 

Tertiary and Cretaceous, 

undifferentiated 

50 0 

- 0 +-' 

Q) 

Q) iobrara UJ 

- a: 5,000 ::::> I 

a... 

1- ~ a: w UJ 0 100 a... 

~ 

w 

1-

10,000 

110 10 0 75 50 

GEOLOGIC TIME (Ma) 

25 0 

Figure 1 (Barker and Crysdale). Burial history of Niobrara Limestone reservoir through time. Modified from a 1982 

thesis by P.A. Tainter. 

A Fluid-Inclusion Technique for 

Determining Peak Temperature and its 

Application to Establish a Refined 

Calibration for the Vitrinite Reflectance 

Geothermometer 

Charles E. Barker and Robert H. Goldstein 

Theory, laboratory experiments, and empirical 

obsetvation suggest that many low-temperature, aqueous 

fluid inclusions in calcite should reequilibrate and 

approach the peak temperature (Tpk) during natural 

overheating. Plots of homogenization temperature (Th) 

and Tpk for systems now at peak temperature (fig. 1, 

facing) demonstrate a direct relationship between the 

variables. Although caution should be applied, the 

relationships suggests that Th of fluid inclusions in calcite 

may be a useful measure of peak temperature. 

Relationships between Tpk, heating duration, and 

thermal maturation of sedimentary organic-matter have 

been obscured by imprecise geologic data. This study 

uses the Th approximation of Tpk and compares it to 

mean random vitrinite reflectance (Rm) (fig. 2, p. 8) to 

develop a refined calibration for the vitrinite reflectance 

geothermometer. Fluid-inclusion and Rm data were 

measured or compiled from diverse geologic systems that 

have been at peak temperature from 104 to millions of 

years. Present Tpk ranged from 72 to 345 °C, Th from 55 

to 347 °C, and Rm from 0.4 to 4.6 percent, spanning the 

temperature and thermal-maturity range associated with 

6 

burial diagenesis, hydrothermal alteration, and lowgrade metamorphism. The refined calibration is: 

ln(Rm) = 0.00776(Tpk)-1.24. 

The strong correlation (r = 0.90) between Tpk and 

Rm in these systems suggests that peak temperature is 

the major control on thermal maturation. 

Fractal Geometry, Chaos Theory, and 

Their Application in the 

Petroleum Industry 

Christopher C. Barton 

Fractal geometry and chaos theory provide a 

means of mathematically describing and modeling the 

complex repetitive patterns which earth scientists map, 

measure, and describe in ever-increasing detail. Fractal 

geometry is a branch of mathematics for quantifying how 

the geometry of self-similar systems changes from one 

scale to another. The self-similar repetition of many 

geologic patterns over a range of scales is demonstrated 

by the need to place an object of known size, such as a 

coin, hammer, or person, into photographs of geologic 

features in order to establish scale. A useful property of 

fractals is that small pieces are representative of the 

whole, and this permits prediction from the geometry of 

a small sample to the geometry of the larger system over 

a wide range of scales. The geometry of a fractal pattern 

is represented by a fractional number, termed the fractal 
~400 (f) 

::J 

(f) 

Q) 

u 

Q) 300 L 

::J 

+-' 

0 

L 

Q) 

0... 

~ 200 IE 

::J 

E 

X 

~ 100 

0 0 

0 

0 

0 

N 

0 

0 

n 

0 

0 

~ 

Homogenization Temperature (Celsius) 

Figure 1 (Barker and Goldstein). Present maximum temperature (Tmax) versus the mean 

(stars) and modal (squares) homogenization temperature (Th) in calcite. Only data from 

systems now at maximum temperature and that have a measured value (bottom hole 

temperature) or a geothermal gradient reported are included. A 45 degree line is shown to 

illustrate perfect 1:1 correlation between Th and Tmax. 

dimension. The scale over which a fractal dimension 

applies is bounded by the upper and lower fractal limit. 

Many geologic patterns have been shown to be 

fractal, including reservoir heterogeneity, size and spatial 

distributions of pores, sequences of stratigraphic 

thickness, size and spatial distribution of petroleum 

reservoirs, fracture networks, porous-media flow, 

tributary river patterns, and topography. Fractal 

geometry provides a method for generating synthetic 

geometric analogs once the fractal dimension of the 

natural pattern has been determined. Fractal geometry 

also permits extrapolating geologic patterns from a onedimensio~al sample (boreholes) to two or three 

dimensions. 

Chaos theory studies the paths along which nonlinear differential equations converge upon multiple 

solutions termed strange attractors. The paths are 

generated by iterating nonlinear equations and plotting 

7 

the pattern of the solutions. Initially, the solutions plot 

along a single path, but with continued iteration the 

solution path bifurcates into two, four, eight, etc. 

solutions in what is called period doubling. The cascading 

pattern of period doubling of solutions as one 

approaches the boundary of chaos is often a fractal 

pattern. The ratio of bifurcation for all iterated nonlinear 

differential equations that follow the period-doubling 

route to chaos has been found to be a universal constant, 

like pi, known as the Feigenbaum number, 4.6692 .... 

Iteration of nonlinear equations provides a new basis for 

modeling the dynamic systems of nature. 

Fractal geometry and chaos theory are major 

advances over previous methods for quantifying complex 

patterns encountered in nature. They provide methods 

for creating highly complex, detailed, and accurate 

synthetic analogs of natural systems. They redefine the 

way we think mathematically about the behavior of 
10 

.r-.... 

..__. ~ 

Q) 

u 

c 

0 

-+-' 

u 1 Q) 

"+-

Q) 

ct: 

Q) 

-+-' 

c 

!..... 

-+-' 

> 

0.1 

0 0 0 0 

0 

n 

0 

0 

~ 

0 0 ~ N 

Tmax from Th (Celsius) 

Figure 2 (Barker and Goldstein). Maximum temperature (Tmax) from homogenization 

temperature (Th) (squares) of aqueous inclusions in calcite versus vitrinite reflectance 

(Rm). The plotted line is computed from the reduced major axis regression equation given 

in the text. Present Tmax (crosses) versus Rm is also plotted in figure 2 for comparison but 

was not included in the regression analysis. We preferentially used Th mode to estimate 

Tmax for this plot, but in a few cases only Th mean was available (as noted in 

supplementary data). 

natural systems, much as the theory of relativity brought 

a deeper level of understanding to physics. Like other 

branches of mathematics, they do not necessarily provide 

a physical or mechanistic understanding. However, in 

natural systems, fractal behavior often breaks down or 

changes to a different fractal dimension at scales where 

the physics changes. Systems that exhibit fractal scaling, 

such as earthquakes, have been shown to be selforganized critical phenomena, which means that they 

internally establish their own dynamically stable critical 

points. A challenge for the future will be to develop a 

method to go from a fractal pattern in nature to its 

governing nonlinear iterated equation. 

The application of fractal geometry in the earth 

sciences has focused on demonstrating that geologic 

patterns are fractal, and on reporting the fractal 

dimension and the range of scales over which the 

dimension applies. Examples of published studies of 

interest to the petroleum industry are as follows. The 

topography of pore surfaces in sandstones, shales, and 

carbonates and the size distribution of pore volume in 

sandstones were shown to be fractal in the range 10-9

-10-4 

m with fractal dimensions 2.27-2.90 and 2.55-2.75, 

8 

respectively, in a series of seven papers by Krohn, Katz, 

Thompson, and others between 1985 and 1988. The 

initial potential for gas wells and the cumulative gas 

production in Upper Devonian shales of West Virginia 

were found to be fractal with dimension 1.46-2.0, as 

calculated by LaPointe from variograms published in 

1988 by Hohn. A series of papers by Hewett, Arya, and 

others published between 1985 and 1988 has shown that 

in petroleum reservoirs, dispersivity in the range 

5-10,000 m and porosity in the range 1-300 mare fractal 

with dimensions of 0.75 and 1.13-1.30 respectively. 

LaPointe, in a 1988 study, has shown that fracture 

densities in the range 0.2-25 m are also fractal with the 

dimension 2.37-2.69. In a 1987 paper, Maloy and others 

have shown that the viscous fingering patterns of lowviscosity fluid (air) penetrating a two-dimensional porous 

medium filled with a high-viscosity fluid (glycerin) are 

fractal, with a dimension of 1.64. The size frequency of 

fault offsets for faults in the range 0.1 to 1,000 m in 

length has been shown in Villemin's 1987 study to be 

fractal with a dimension of 1.2. Finally, in a series of 

papers published between 1985 and 1987, my coworkers 

and I have reported that the spatial and size distributions 
of fractures in the range 0.02-3,000 m within fracture 

networks are fractal, with the dimension 0.5-0.7 in drill 

holes and 1.6-1.8 in planar sections. We have 

demonstrated that rock-fracture networks are fractal and 

that one can use data from a one-dimensional drill-hole 

sample of fracture spacing to predict the two- and 

three-dimensional spatial attributes of the fracture 

network. 

The use of fractal geometry and chaos theory in the 

earth sciences has increased greatly in the past 5 years. 

Fractal geometry and chaos theory will redefine the way 

that we conceptualize many natural systems in the earth 

sciences. I expect that many geophysical records will 

prove to be fractal in both time and space. I expect that 

the size and spatial distributions of oil and gas fields and 

the compartmentalization of permeability within them 

will prove to be fractal, just as the porosity and dispersivity have proven to be, and that this will have significant 

impact on drilling strategy and resource assessment. 

Subsurface Exploration with the Aid of 

Borehole Gravimetry 

Larry A. Beyer 

Borehole gravity (BHG) measurements are unique 

among well-logging measurements because they (1) 

respond directly to the bulk density of rock formations 

surrounding a well, (2) investigate surrounding volumes 

of rock greater by at least three orders of magnitude than 

those investigated by conventional well-logging methods, 

(3) provide profiles of vertical density that have high 

relative or absolute accuracy, and (4) are unaffected, for 

practical purposes, by well casing, cement, or borehole 

fluids. With sufficient independent information, BHG 

density profiles can be reliably converted to porosity 

profiles. In some cases, BHG density profiles may 

delineate zones whose relatively low density can be 

attributed to indicate the presence of hydrocarbons. 

Also, anomalous gravity effects due to lateral variations 

of density or porosity in the vicinity of the borehole may 

be detectable and interpretable in terms of geologic 

structure or facies changes. 

Hundreds of mostly commercial BHG surveys have 

been made worldwide since the U.S. Geological Survey 

(USGS) pioneered development in 1966-1967 of the 

reliable, high-precision LaCoste and Romberg borehole 

gravity meter. Although results of most commercial 

surveys remain proprietary, work by the USGS and some 

published reports of industrial surveys show that BHG 

measurements can be applied to (1) pre-discovery 

exploration for porous reservoirs, (2) post-discovery 

evaluation and monitoring of porous (principally 

9 

hydrocarbon-bearing) reservoirs, (3) evaluation of rock 

density and porosity or subsurface structure for 

engineering and other purposes, ( 4) evaluation of, or aid 

to other surface and downhole geophysical methods, and 

(5) fundamental studies of rock density and porosity in a 

variety of geologic settings. 

Recent BHG studies by the USGS in the Kuparuk 

oil field (Alaska), Enewetak Atoll (Marshall Islands), 

Cajon Pass Scientific Drill-hole (California), and Ventura oil field (California) illustrate the latter four 

application areas. These BHG studies evaluated (1) an 

unproduced oil reservoir and a possible gas hydratebearing interval (Kuparuk field), (2) perturbing effects of 

a thermonuclear event on backreef deposits of Pliocene 

to Holocene age (Enewetak Atoll), (3) local geologic 

structure and performance of conventional well logs in 

crystalline basement rocks (Cajon Pass), and (4) effects 

of abnormally high pore:.. fluid pressure on the porosity of 

Pliocene turbidite sandstones (Ventura field). 

Present-day BHG logging sondes have outer 

diameters that generally range from 10.8 to 12.7 em ( 4.25 

to 5.0 in.), and they contain heat-shielding dewar flasks. 

These flasks give the instrument package resident times 

of several tens of hours at well temperatures of about 200 

oc (392 °F). A new USGS logging sonde with high 

temperature and pressure tolerance (and high corrosion 

resistance) is under development. This new sonde should 

permit BHG surveys to depths of about 6 to 9 km (19,700 

to 29,500 ft), depending on drill-hole temperature and 

fluid pressure. If successful, use of this new sonde should 

provide unique data about the porosity of rocks at these 

depths. 

Subsurface Studies, Santa Maria 

Province, California 

K.J. Bird, P.H. McClellan, and T.R. Bruns 

Seismic-reflection records and well data are being 

analyzed to provide a subsurface geologic framework for 

the U.S. Geological Survey's Santa Maria project. This 

project, jointly sponsored by the Evolution of 

Sedimentary Basins and Onshore Oil and Gas 

Investigations Programs, is a basin-evolution study 

focusing on the geologically complex and tectonically 

active south-central California margin. The area 

embraces several basins and basin fragments: the Santa 

Maria (onshore and offshore), Pismo, Huasna, Sur, 

Santa Lucia, and western Santa Barbara-Ventura. These 

basins have many similarities, including generally 

synchronous formation at about the end of the Oligocene, basin development on a complex assemblage of 

Mesozoic tectonostratigraphic terranes, and basin fill 
consisting of Neogene clastic marine and nonmarine 

deposits, minor volcanic rocks, and organic-rich biogenous deposits (Monterey Formation). Despite these 

similarities, basin origins are controversial, and basin 

paleogeographies uncertain. 

Large petroleum resources, collectively more than 

a billion barrels of oil, and a long exploration history are 

primarily responsible for an abundance of subsurface 

information in these basins; yet relatively few published 

studies since the early 1950's provide subsurface 

documentation. We are constructing a network of wellcorrelation sections, supplemented where possible with 

seismic-reflection data and synthetic seismograms, which 

integrate surface and subsurface geology, one basin with 

another, and the onshore with the offshore region. 

Offshore seismic records offer an opportunity for 

improved stratigraphic understanding, including the 

discrimination of tectonic from eustatic sea-level 

patterns, by calibrating the stratigraphy penetrated in 

wells with the seismic-reflection records. Subsurface 

information will contribute to facies studies and paleogeographic reconstructions necessary to test hypotheses 

of basin origins. 

Petrography of Permian "Gondwana" 

Coals from Boreholes in 

Northwestern Bangladesh 

Neely Bostick, Hal Gluskoter, 

M. Nazrul Islam, and Q.M. Arifur Rahman 

In northwestern Bangladesh, drilling through 

alluvium and Tertiary cover at sites of local low-gravity 

anomalies has confirmed the presence of Permian 

sedimentary rocks in depressions that may be as much as 

a thousand meters deep in the crystalline basement. 

These sedimentary rocks contain low-sulfur, high-volatile 

bituminous coals reported in seams as thick as 40 meters. 

We describe coals from corehole GDH-40 in the Barapukuria coal area and from GDH-45 in the Khalaspir 

area, 250 and 225 km northwest of Dhaka. 

Judging by 16 spot samples from GDH-40 and 41 

bench channel samples from GDH-45, many of these 

coals have features of "Gondwana coal" type. Highmineral ( > 30 percent) coals are mostly a nonlayered 

"plum pudding" of minerals and inertinite grains in an 

inertinite groundmass-with little vitrinite. True fusinite 

is rare in high-inert samples, but occurs in some vitrains. 

A half-dozen samples contain more than 70 

percent vitrinite and have microscopic aspects in 

common with non-Gondwana bright banded coals, 

though with more total inertinite (10-30 percent). But 

most of the samples would stand apart from the usual 

10 

bright or gelititic coals of European and North American 

commerce and would be classed as semi-dull or inertogelitite types. 

Well-layered grains observed all contain very 

dispersed, fine cuticle-spore chaff that may constitute as 

much as 5-10 percent of the organic volume; none of the 

samples would be classed as liptinitic or sapropelic. 

Neither separate resinite nor sclerotinite was seen. 

Visible pyrite is in veinlets or small nodules; framboids 

and dispersed pyrite are absent. 

Only the channels sampled from GDH-45 are of 

quality to permit quantitative evaluation. These are 10 

benches each (1!10 to 3m thick) taken from core of the 

three major seams; the upper (14m) and middle (16m) 

seams are separated by only 2 m of non-coal rock, 

whereas the lower (13 m) is 33 m below the base of the 

middle seam. Ash in the coal ranges from 8 to 52 percent 

(dry basis) in individual benches, with composite seam 

averages of 15, 14, and 24 percent. Inertinite is 7 to 100 

percent in benches, but averages 41, 54, and 67 percent 

com posited in the upper, middle, and lower main seams. 

In GDH-45 the free swelling index reaches 7.5 in 

several vitrinite-rich benches, which can indicate good 

coking coal, but the PSI value in mined coal may be as 

low as 3 depending on how the benches are combined 

during mining. Inertinite, and to some extent the ash, 

increases toward the top of each main seam so the 

bottom benches would yield the most valuable first mine 

slices-3 m, 7 m, and 1 m of coal with PSI about 6, ash 12 

percent, inertinite 10-30 percent and 30 percent volatile 

matter (d.a.f.). Some benches with extremely high inert 

content, such as the top 7 m of the lower seam, might be 

mined especially for blending coke, and would have an 

advantage for handling that fusinite dust would be slight, 

unlike the case of many inertinite-rich coals. 

In the Barapukuria borehole samples, from depths 

of 200 to 500 meters, the average vitrinite "A" random 

reflectance ranges from 0.60 to 0.80 percent Ro, and 

vitrinite "B" averages from 0.55 to 0.65 percent. In 

borehole GDH-45, from 287 to 442 m, the reflectance of 

grains of crushed vitrinite ranges from 0.79 to 0.94 

percent. In individual cases the vitrinite is difficult to 

define because of semivitrinite at higher reflectance (in 

several samples a distinct peak on reflectance 

histograms) and because of surface bitumen films or 

resinous(?) inclusions at lower reflectance. 

Samples from deeper in borehole GDH-40 contain 

more fluorescent vitrinite, visible mobile bitumen, and 

fluorescing minerals than do shallow samples; and the 

deeper levels, as well as all of GDH-45, can be 

considered to have entered the "main phase of bitumen 

generation" of organic thermal maturation. 
(Bostick) Many Permian coals from equatorial and southern lands are markedly different from northern commercial coals. 

These "Gondwana" coals generally have a high content of clastic mineral grains, and the concentrated fossil woody material 

which forms the coal is weathered and broken. The latter circumstance shows in maceral analyses in which vitrinite (the 

dominant component of other coals) is only 3()-60 percent, while inertinite, originating from oxidatively altered wood, is 

dominant. Newly discovered coals in Bangladesh share these "Gondwana" features as shown here. In the left photomicrograph (0.37 mm actual width) the distinctive good preservation of woody tissues in a piece of semifusinite contrasts with the 

enclosing matrix of broken oxidized woody fragments. The lack of crushing in the large piece is a consequence of the inertness 

of the entire coal at the time of deposition and a relatively strong resistance to compression. This sample is the uppermost 

bench of the upper main seam; it contains 35 percent vitrinite and 58 percent inertinite, with 12 percent ash. The right 

photomicrograph (0.45 mm actual width) shows coal 3 m deeper in the same seam where vitrinite is 65 percent and inertinite 

30 percent. Round phlobaphinite cell fillings in semifusinite make up much of the photo, but enclosing matrix in the lower part 

is vitrinite that was still a humic gel when deposited, though not fluid enough to penetrate the semifusinite. The bright filling at 

upper right is pyrite, which in these coals is vein and nodule precipitate, not bacteriogenic aggregates, and is associated with 

zinc sulfide. The photos show polished surfaces under immersion liquids. By Neely Bostick. 

GLORIA Images from the Gulf of Alaska 

and British Columbia-Subduction 

Zones, Transforms, and Channels 

T.R. Bruns, P.R. Carlson, A.J. Stevenson, M.A. 

Fisher, H.F. Ryan, D.M. Mann, Maxwell Dobson, 

Quentin Huggett, Lindsay Parson, and 

N.G.T. Fannin 

GLORIA data obtained during 1986, 1988, and 

1989 in the Gulf of Alaska show the sea-floor 

11 

morphology from Unimak Pass to Dixon Entrance, from 

the shelf break seaward to about 400 km. An additional 

70-km-wide swath was imaged along the British 

Columbia margin to follow the trace of the Queen 

Charlotte fault south of Dixon Entrance. Major features 

seen include the following continental-margin deformational structures and submarine-channel systems: (1) 

The Aleutian convergent margin is characterized by 

canyons and numerous slumps along the upper and 

middle slope. Unimak Ridge is a prominent midslope 

feature from Sanak Island to Unimak Pass. Along the 
lower trench slope, the structure ranges from highly 

discontinuous folds to long continuous folds. (2) 

Southeast of the Aleutian Trench, ocean plate structural 

and bathymetric features are either parallel to magnetic 

anomalies, or are parallel to the trench and caused by 

normal faults as the plate bends into the Aleutian Trench 

subduction zone. (3) The margin between Middleton 

Island and Cross Sound is commonly either extensively 

cut by dendritic drainages or covered by glacially derived 

sediment. Large actively growing structures are present 

beneath the slope between Middleton Island and Pamplana Spur, but they are notably absent from Pamplona 

Spur to Cross Sound. (4) From Cross Sound to south of 

the Queen Charlotte Islands, the active trace of the 

Queen Charlotte fault is strikingly imaged as a narrow 

linear feature composed of ridges and troughs that have 

vertical offset. Horizontal offset is visible on a canyon 

wall and on offset channels. Numerous large anticlines 

are present seaward or, and trend parallel to, the fault. 

The active fault trace steps westward at the Tuzo Wilson 

Knolls, which structurally may be part of a small 

spreading ridge segment or pull-apart basin. (5) On the 

abyssal plain, turbidite channels form three separate 

drainage systems. The Surveyor channel system is 

comprised of tributary channels that arise along the 

margin between Pamplona Spur and Alsek Canyon, and 

that coalesce on the abyssal plain into a single channel 

(Surveyor channel) which ends at the Aleutian Trench 

southeast of Kodiak Island. The Chirikof channel system 

(new name) similarly arises from the margin between 

Fairweather Ground and Cross Sound, eventually 

forming a single channel that terminates in turbidite fans 

south of the Kodiak-Bowie Seamount chain. The 

Mukluk-Horizon channel system starts along southeast 

Alaska, with drainages from submarine fans joining to 

form Mukluk and Horizon channels. Both channels end 

more than 1,000 km away on the Tufts abyssal plain. 

Laser Raman and Luminescence 

Spectroscopy of Carbonate 

Minerals-Progress Toward 

Nondestructive Microprobe Techniques 

for Stable Isotopes, Trace Elements, and 

Organic Matter in Zoned Cements 

R.C. Burruss, T.G. Ging, K.R. Cercone, 

V.A. Pedone, and T.S. Hayes 

Carbonate cements in reservoir rocks and 

migration pathways may record the chronology (paragenesis, radiogenic isotopes), temperature (stable isotopes, 

fluid inclusions), redox conditions (Fe/Mn), and 

composition (trace elements, fluid inclusions) of paleo12 

fluids. However, cements are commonly zoned at the 

micrometer scale and require microprobe techniques to 

resolve the cement stratigraphy and to allow petrologists 

to infer aspects of diagenetic history and paleo-fluid flow. 

Laser Raman and luminescence spectroscopy are new 

microprobe technologies for nondestructive trace 

analysis of geologic materials such as these cements. 

Raman spectroscopy examines the vibrational 

energies of molecules, polyatomic ions, and crystal 

lattices, whereas luminescence (fluorescence and 

phosphorescence) spectroscopy examines the electronic 

energies of atoms and molecules. Laser spectroscopy 

through a microscope has high spatial resolution because 

objectives of 50 X or higher magnification focus the laser 

beam to a diffraction limited spot of < 2 ~m. The USGS 

laser Raman microprobe laboratory has an ISA U-1000 

spectrometer with an Olympus microscope, a SpectraPhysics argon ion laser source, a photon-counting photomultiplier detector, and an intensified, 700-channel 

diode array detector. The laser operates at 11 discrete 

wavelengths in the ultra violet (351 and 364 nm) and the 

blue-green (454 to 528 nm) for observation of Raman 

and luminescence spectra. 

Vibrational energy levels of molecules are sensitive 

. . b . . h 180 £ 160 d R to tsotoptc su stttutton, sue as or , an aman 

spectroscopy can detect isotopically substituted 

molecules at natural abundance. Raman measurements 

of stable isotope ratios are difficult because the natural 

abundance of 13C is 1.11 percent and 180 is 0.204 

percent. Geochemical variations in the isotope ratio of an 

unknown (Runk) are measured in parts per thousand 

(ppt) relative to the ratio in a standard (Rstct), calculated 

as: 

Therefore, variations in the o value of 1 ppt in 13C 

or 180 are, in fact, variations in the absolute abundance 

of 1 part in 105 in 13C/ 2C and 2 parts in 106 in 18 0/ 60. 

Counting statistics are the fundamental limitation, but a 

spectrometer with a single-channel photomultiplier is 

sensitive to noise in the laser intensity which limits the 

precision to ± 10 to 50 ppt, regardless of the total signal. 

Therefore, geochemically useful isotope measurements 

with a standard single-channel Raman spectrometer are 

impossible. Multichannel, intensified, diode array 

detectors measure all isotope peaks simultaneously, 

eliminating laser noise from the spectra. Initial 18 0/ 6

0 

ratios in calcite from 3 of 5 localities (reported in a 1989 

study by Burruss, Ging, and D. Carlson) using a multichannel detector have precisions (±7 ppt) limited by 

counting statistics. However, the accuracy of the Raman 

measurement compared to ratio mass spectrometry is 

limited by background fluorescence from the mineral. 
Current research is aimed at improving the precision to 

±2 ppt o18 0 and eliminating interference from 

fluorescence. 

Fluorescence microscopy of carbonate rocks is an 

important tool for diagenetic and petroleum migration 

studies. Spatially resolved spectra can help identify the 

fluorescence activators and their concentrations in zoned 

minerals. Initial studies have distinguished organic and 

Mn2 + activation in red algae, Mn2 + activation and 

concentration in zoned calcite cement from the Canning 

basin, Northwestern Australia, and Mn2 + activation, 

Pb2 + co activation, and Fe2 + quenching in zoned 

dolomite from the lower Paleozoic of northeastern 

Oklahoma, northern Arkansas, and southern Missouri. 

Identification of Pb2 + activation is tentative because Pb 

levels are below the detection limits of the electron 

probe. However, identifying Pb zoning may be critical 

evidence for constraining models of Pb transport in the 

regional fluid flow system that formed the world-class 

Pb-Zn deposits of the southern midcontinent. Research 

in progress is aimed at identifying organic activation of 

carbonate fluorescence in petroleum source rocks and 

migration pathways. 

Coal Availability StudiesA Progress Report 

M. Devereux Carter, Nancy K. Gardner, Richard 

E. Sergeant, Elizabeth V.M. Campbell, and 

Nick Fedorko, Ill 

Many federal estimates of the Nation's coal 

resources do not account for numerous factors that could 

inhibit the availability of coal for development. As a 

result, these estimates may be mistakenly optimistic for 

long-term policy-planning purposes. In 1987, a 

cooperative program between the U.S. Geological 

Survey (USGS) and State geological agencies of 

Kentucky, Virginia, and West Virginia was initiated to 

identify the major current constraints to coal mining that 

could inhibit the availability of coal resources, and to 

estimate the amount of coal resources actually available 

for development within the Central Appalachian region. 

This program has been tested in nine 7.5-minute 

quadrangle areas (four in Kentucky, three in West 

Virginia, and two in Virginia) to determine if the 

identified constraints to mining in the region would 

significantly affect the availability of coal for 

development. It is estimated from these studies that only 

about 53 percent of the original resources of these 

quadrangles will be available for mining, before the 

application of recovery factors. The amount of coal that 

may actually be recoverable may only be about 30 to 40 

13 

percent of the original resource. The nine areas were 

selected to be representative of their general localities so 

that the results might be extrapolated to their 

surrounding regions. A pilot study was completed early 

in 1988 and the first eight studies to be formally funded 

under this program were completed by September 1989. 

Restrictions were identified by consultation with 

local coal-industry engineers, geologists, mine operators, 

and State and federal regulatory personnel. Land-use 

restrictions applicable to the study areas resulted from 

the presence of power lines, pipelines, cemeteries, oil and 

gas wells, towns, major streams, public roads, railroads, 

airports, national and State parks, and one large forest 

preserve. Technologic constraints included coal beds 

considered too thin or too deep to mine, buffer zones 

around active or abandoned mines, mined and minable 

coal beds too close to one another, oil and gas wells 

penetrating underground-minable coal beds, and such 

geologic factors as washouts, faults, disturbed areas, and 

organic constituents that prevent rapid and complete 

burning. Computer programs of the USGS National Coal 

Resources Data System (NCRDS) were used to (1) 

combine and manipulate all data on coal-bed thickness 

and depth-of-burial with the constraints to mining, and 

(2) calculate original, remaining, and available resources. 

There is a wide variation among the individual 

resource categories, but the overall results are fairly 

consistent for the study areas. Approximately 53 percent 

(ranging from 27 to 64 percent) of the original resource 

is estimated to be available for mining. Coal mined and 

lost-in-mining accounts for 12 percent of the reduction of 

the original resource, whereas land-use restrictions entail 

a 3 percent reduction, and technologic restrictions a 30 

percent reduction. More than 2.5 billion tons of coal are 

estimated to be rendered unavailable for mining by 

land-use and technologic restrictions within the areas 

studied. 

Chemical data are sparse in the areas studied. 

However, statistical analyses of those beds with available 

sulfur data indicate that approximately one-half of the 

available coal resources in these areas could be expected 

to meet current new-source performance standards of 

1.2 pounds S02 per million Btu input. 

Economic considerations (such as mining costs, 

available transportation, and proximity to markets) and 

the application of recovery factors were beyond the scope 

of this study, but if applied, they would further reduce the 

amount of coal estimated to be available. In any case, it 

seems evident that, under current conditions, less than 

one-half of the coal resources remaining in these study 

areas could ever be mined. 

As expected, results of the first nine studies are 

inconclusive in terms of delineating regional trends. 

Studies in about 20 strategically placed 7.5-minute 
quadrangles may be necessary to adequately represent 

the entire Central Appalachian region. 

Sulfur in Coai-NCRDS Applications 

M.D. Carter, S.J. Tewalt, L.J. Bragg, and 

R.B. Finkelman 

The National Coal Resources Data System 

(NCRDS) is a geographic information system (GIS) that 

includes several data bases containing information on the 

sulfur content of coal. Each data base contains different 

types of sulfur data related to sample type, date of 

analysis, and source of data. Table 1 lists pertinent 

information for two of these data bases, BMAL YT (U.S. 

Bureau of Mines AnaLYTical Data) and USCHEM 

(United States GeoCHEMical Data). 

NCRDS sulfur data can be used in a variety of 

applications. For example, data from BMAL YT have 

been utilized to determine mean sulfur contents of 

sampled coal beds in major coal regions in the United 

States (fig. 1 ). Potential S02 emissions (lb S02 per 

million Btu) were derived for coal in the same regions. 

Differences in coal rank (and Btu) between regions were 

reflected in the varying amounts and percentages of 

sulfur that would have to be removed to meet 

Environmental Protection Agency S02 emission limits. 

Data on the forms of sulfur in coal are available in 

the USCHEM data base. As an example of the utility of 

these data, the mean contents of sulfur as pyritic, sulfatic, 

and organic forms have been determined in Eocene coals 

of the Gulf Coast region (table 2). 

In recent coal-resource assessment studies, data on 

sulfur and heating content of coal have been combined 

with information on thickness and mining restrictions. 

Using NCRDS software, the amount of compliant and 

noncompliant available resources has been calculated for 

coal in selected quadrangles. A pilot coal availability 

project examined 22 coal beds in the Matewan 

quadrangle, Kentucky. Although most coal beds are 

either completely above or below the limit, two beds 

contain both compliant and noncompliant resources 

based on an emissions limit of 1.2 lb S02 per million Btu 

for new-source coal-fired power plants (fig. 2, p. 16). 

Natural Gas Hydrates in the Prudhoe 

Bay-Kuparuk River Area of 

Northern Alaska 

Timothy S. Collett 

Gas hydrates are crystalline substances composed 

of water and gas in which the solid-water lattice 

accommodates the gas molecules in a cage-like structure, 

or clathrate: Significant quantities of naturally occurring 

gas hydrates have been detected in many regions of the 

Arctic including Siberia, the Mackenzie River delta, and 

the North Slope of Alaska. Gas hydrates are generally 

regarded as a potential (unconventional) source of 

natural gas. Soviet researchers, however, have 

demonstrated that hydrates are an immediate, 

producible source of natural gas; their Messoyakh gas 

field in the West Siberian Basin has reportedly produced 

about 100 billion cubic feet of gas from hydrates over an 

eight-year period (1971-1978). 

Table 1 (Carter, Tewalt, others). NCRDS data bases containing data on sulfur content of coal 

Type of Total Number of 

Data base Data source Analytical lab Types of samples analyses (in sulfur data thousands) 

BMALYT TotalS U.S. Bur. Mines U.S. Bur. Mines Tipple, delivered 53 

USC HEM TotalS, USGS, State U.S. Bur. Mines, Channel, drill core 13 

forms of S geological Commercial 

agencies 

Table 2 (Carter, Tewalt, others). Arithmetic mean values of sulfur contents (weight percent, as-received basis) for 

Gulf Coast lignites 

[N, number of samples] 

Stratigraphic 

group 

Claiborne 

Jackson 

Wilcox 

Midway 

*Calculated separately. 

N 

26 

13 

149 

10 

Total sulfur* 

0.72 

1.64 

1.01 

2.05 

14 

Pyritic sulfur Organic sulfur Sulfate sulfur 

0.24 0.45 0.04 

0.31 1.36 0.04 

0.36 0.62 0.09 

0.78 0.97 0.30 
0 500 

I 

Figure 1 (Carter, Tewalt, others). Mean sulfur content (weight percent, as-received basis) of raw coal samples from major coal 

regions in the United States as determined from the BMAL YT data base. 

The primary purpose of the U.S. Geological Survey 

Gas Hydrate Project is to identify gas hydrates and to 

evaluate the geologic properties controlling their 

distribution on the North Slope of Alaska. Our North 

Slope studies suggest that the methane-hydrate stability 

zone is areally extensive beneath most of the coastal plain 

province and has thicknesses greater than 3,000 feet in 

the Prudhoe Bay area. Thermal conditions, however, 

preclude the occurrence of gas hydrates in the northcentral part of the National Petroleum Reserve in Alaska 

and in the foothills east of Umiat. 

Gas hydrates have been identified in 34 exploratory 

and production wells by using well-log responses 

calibrated to the response of an interval in one well where 

gas hydrates were recovered in a core by ARCO Alaska 

and Exxon. Most gas hydrates that we have identified 

occur in six laterally continuous Upper Cretaceous and 

lower Tertiary sandstone and conglomerate units; all 

these hydrates are geographically restricted to the area 

overlying the eastern part of the Kuparuk River oil field 

and the western part of the Prudhoe Bay oil field. Many 

wells have multiple gas-hydrate-bearing units, with 

15 

individual occurrences ranging in thickness from 5 to 60 

feet. Most of the gas hydrates occur below the base of 

ice-bearing permafrost; however, high gas readings on 

mud logs from some wells in the Kuparuk River oil field 

suggest that several of the gas-hydrate-bearing units 

extend up-dip into the ice-bearing permafrost sequence. 

Recent drilling and geologic/geochemical sampling have 

revealed the presence of a gas-hydrate/free-gas contact at 

the predicted base of the methane-hydrate stability zone 

in the west end of the Prudhoe Bay oil field. Our 

calculations suggest that the volume of gas within the 

delineated gas hydrates of northern Alaska is 

approximately 8 to 10 TCF (trillion cubic feet) (2.4X 1011 

to 2.9X 1011 m3), or about one-third the volume of 

conventional gas in the Prudhoe Bay field. Because of the 

low drilling density outside the Prudhoe Bay-Kuparuk 

River area, many more gas hydrate occurrences may 

exist. 

Stable carbon isotope geochemical analysis of well 

cuttings in the Kuparuk River area indicates that rocks 

within and below the zone of hydrate stability contain a 

mixture of microbial and thermogenic gas. We suggest 
Matewan 

quadrangle 

Figure 2 (Carter, Tewalt, others). Areas underlain by the Upper Elkhorn No. 1 B coal bed in Matewan 7.5-minute quadrangle, 

Pike County, Kentucky, Appalachian basin. Heavy line separates areas of compliance (widely spaced pattern) and 

noncompliance (closely spaced pattern) coal. Blank, no coal. 

that the identified hydrates originated from a mixture of 

deep-source thermogenic gas and shallow, microbial gas 

that was either directly converted to gas hydrate or first 

concentrated in existing traps and later converted to gas 

hydrate. We postulate that the thermogenic gas migrated 

from deeper reservoirs along the same faults thought to 

be migration pathways for the large volumes of shallow, 

heavy oil that occur in this area. 

Cretaceous and Tertiary Sagavanirktok 

Formation in the Prudhoe Bay-Kuparuk 

River Area, Northern Alaska 

Timothy S. Collett and Kenneth J. Bird 

Detailed well correlation sections and ongoing 

USGS studies of gas hydrates and basin evolution have 

16 

provided new insights on the stratigraphic framework of 

the Cretaceous and Tertiary Sagavanirktok Formation in 

the Prudhoe Bay-Kuparuk River area of the North 

Slope. The Sagavanirktok Formation is the youngest part 

of the Brookian sequence, a sequence composed of 

siliciclastic rocks whose provenance is the Brooks Range, 

to the south. The study area overlies the axis of the 

Barrow arch and marks the boundary between a foreland 

basin to the south (Colville basin) and a passive margin 

(Beaufort margin) to the north. The principal oil 

accumulations of the Brookian sequence in the Prudhoe 

Bay-Kuparuk River area are in the informally named 

West Sak and Ugnu sands of the Sagavanirktok 

Formation. ARCO Alaska estimates that the combined 

oil in-place in these two reservoirs could be as large as 40 

billion barrels. Our studies of gas hydrates, crystalline 

substances composed of water and gas, within the Saga-
vanirktok Formation suggest that the volume of methane 

gas within the hydrates of this area is about 8 to 10 trillion 

cubic feet at standard temperature and pressure. 

The Sagavanirktok Formation consists of Upper 

Cretaceous and Tertiary shallow-marine shelf and delta 

plain deposits composed of sandstone, shale, 

conglomerate, and coal. The areal distribution of the 

Sagavanirktok Formation is limited to the coastal plain of 

the eastern half of the North Slope and the adjacent 

continental shelf. The regional structure of the Sagavanirktok Formation in this area is a gentle (1 o -2°) 

northeasterly-dipping monocline. The present regional 

northeast tilt is the combined result of sediment loading 

and continued thermal subsidence of the Beaufort 

margin. In the study area the Sagavanirktok Formation 

thickens from southwest (=1,000 m) to northeast 

(=2,000 m), and conformably overlies marine shale of 

the Canning Formation. Depositional strike migrated 

from a nearly north-south trend in Late Cretaceous time 

to its present west-northwest trend in about Eocene time. 

Detailed well-correlation sections show the Sagavanirktok Formation in this area consists of complexly 

interbedded marine and nonmarine deposits that include 

at least one regional unconformity. The lowermost 

sandstone sequence within the Sagavanirktok Formation 

includes the West Sak and Ugnu sands. The Late 

Cretaceous West Sak interval represents transitional 

inner-shelf and delta-front deposits. The primary West 

Sak reservoirs are within the upper part of the sequence, 

which consists of two distinct and laterally extensive 

sandstone units. The West Sak interval is separated from 

the overlying Ugnu interval by a regionally extensive 

marine (30-45-m-thick) mudstone. The Late 

Cretaceous-early Tertiary Ugnu interval (80 to 100 m 

thick) consists of a series of interbedded sandstone and 

mudstone units. Overlying the Ugnu interval is a 

250-300-m-thick nonmarine interval composed of 

numerous fining-upward channel and overbank siltstone 

and sandstone units. This nonmarine sequence is 

overlain by a 200-300-m-thick interbedded sandstone 

and mudstone marine sequence that was deposited 

during a basin-wide marine transgression in Eocene 

time. This sequence thins southwesterly and 1atera11y 

coarsens to a sandstone in the eastern part of the 

Kuparuk River field. The upper boundary of this marine 

sequence is an erosional unconformity. East of Prudhoe 

Bay field, near the delta of the Sagavanirktok River, this 

unconformity has eroded part of the underlying marine 

sequence; however, to the southwest into the Kuparuk 

River area, the unconformity apparently disappears and 

the sequence becomes conformable. The rocks overlying 

the unconformity are generally of uniform composition 

both lateraliy and verticaliy in the section, and appear to 

have been deposited in a delta-plain environment. 

Individual sandstone units in this interval thicken to the 

17 

northeast, which may represent the direction of the 

northeast-prograding deltaic depocenter. Other unconformities may occur within the Sagavanirktok Formation; 

however, with our present well-log data base we are 

unable to identify any additional hiatuses. 

In the Kuparuk River area the Sagavanirktok 

Formation is cut by northwesterly-trending high-angle 

normal faults, generaliy downthrown to the east. A 

similar set of northwesterly-trending faults cut the older 

rocks in this area, suggesting a genetic linkage with the 

faults within the Sagavanirktok Formation. These faults 

are important in that they may serve as conduits for oil 

and gas migration from the underlying Prudhoe Bay 

field. Geochemical similarities suggest that oils, and 

presumably the associated gas, within the Sagavanirktok 

Formation were "spilled" from the underlying Prudhoe 

Bay Sadlerochit Group reservoir as a consequence of 

regional tilting during middle to late Tertiary time. We 

also note that the shallow heavy-oil and gas hydrates 

occur either up-dip from or near one of the major 

through-going faults, the Eileen fault zone. 

Comparative Evolution of Western North 

America and Southern Kazakhstan, 

U.S.S.R.-Two Early Paleozoic Carbonate 

Passive Margins 

Harry E. Cook and Michael E. Taylor 

The ancient continental margin of western North 

America formed when a rift and spreading center 

developed within Laurentia and fragments drifted apart, 

forming a new ocean-the proto-Pacific. Stratigraphic 

backstripping and thermal subsidence curves show that 

the main breakup and onset of spreading probably 

occurred in the Late Proterozoic and earliest Cambrian. 

In Nevada, lower Paleozoic carbonate sediments were 

deposited on a distally steepened, nonrimmed carbonate 

ramp. Thus, deep-water carbonate environments 

characterized the platform margin and slope in central 

Nevada with shoal-water carbonate environments being 

restricted to eastern Nevada and western Utah. However, 

in some of the more northerly parts of western North 

America, such as in east-central Alaska, the carbonateplatform margin was characterized by ooid sand-shoal 

environments. With continued separation of continental 

fragments and postrift thermal subsidence, the western 

edge of North America became a site where 3-5 km of 

shoal-water and deep-water carbonate rocks 

accumulated during a 200-m.y. interval from Early Cambrian through Late Devonian time. This thick carbonate 

megaplatform reflects the tectonic stability of the Laurentian continental margin over a width of several 

hundred kilometers. 
Southern Kazakhstan is composed of several 

amalgamated microcontinental blocks that exhibit a 

complex evolution, which began with Late Proterozoic 

(Riphean) rifting of continental crust. During rifting, a 

passive continental margin developed in the region of the 

Malyi Karatau-Tien Shan structural belt in southern 

Kazkhstan and western People's Republic of China. In 

contrast to western North America, which evolved as a 

relatively stable continental margin attached to the craton, this central Asian continental margin was broken 

into a series of large isolated blocks during rifting. With 

continued spreading and postrift thermal subsidence 

these isolated blocks became the loci for shallow-marine 

carbonate sedimentation during the Late Proterozoic 

(Vendian) and early Paleozoic. In the Malyi Karatau 

region, one of the isolated blocks became the site of a 

40-km-wide carbonate seamount. Sedimentation on the 

seamount kept pace with postrift thermal subsidence 

resulting in at least 1,000 m of carbonate sediments. Thi~ seamount was virtually devoid of any siliciclastic input. 

The oceanward margins of the seamount became the 

sites of robust Epiphyton cyanobacterial bioherms and 

mobile ooid-sand shoals. Seamount interior envir~nments were characterized by shallow subtidal lagoons 

wtth scattered, small Epiphyton mounds, and supratidal 

islands. This feature, named the "Aisha-Bibi seamount" 

in honor of a twelfth-century Kazakh princess, is the 

oldest early Paleozoic seamount reported in the 

literature. It may be one of many carbonate seamounts 

that formed an early Paleozoic archipelago extending 

from southern Kazakhstan southeastward into the Tien 

Shan region of People's Republic of China. 

During the Late Cambrian and Early Ordovician, 

sedimentation in both western North America and Kazakhstan was dramatically punctuated numerous times by 

carbonate-platform-margin collapse during sea-level 

lowstands. In western North America rapid seaward 

progradation of the continental margin, in combination 

with eustatic changes, resulted in mass failure of deepwater slope deposits. In Nevada, these failed slope 

deposits were transported seaward as submarine slides 

channelized debris flows, and turbidity currents, resultin~ in the formation of slope-generated carbonate submarine 

fans. Some of the carbonate fan facies are admixed with 

siliciclastic sands, which were probably transported 

across the shelf during sea-level lowstands. Shallowwater carbonate sites to the east developed disconformities as represented by faunal hiatuses, as well as solution 

surfaces. In Alaska, where the continental shelf/slope 

break was dominated by ooid-sand shoals, 75-km-wide 

segments of this margin collapsed and were transported 

downslope by boulder-bearing mass flows. Here the 

redeposited debris formed linear carbonate aprons 

several hundred meters thick that are composed of ooid 

and slope-derived lime mudstone clasts. 

18 

During early Paleozoic eustatic events in Kazakhstan, 200-800-m-wide segments of the Aisha Bibi 

seamount margin collapsed. These collapsed margins 

were transported seaward as channelized boulderbearing debris flows, turbidity flows, and submarine 

slides. Repeated large-scale, episodic mass-transport 

processes contributed to the development of 500-m-thick 

carbonate submarine fans that extend several kilometers 

onto the basin plain. Interior parts of the seamount 

exhibit tidal-flat facies and solution breccia that may 

correlate with sea-levellowstands. 

Evidence for four coeval sea-levellowstands occurs 

in both North America and in the Malyi Karatau region 

of southern Kazakhstan. Timing of these four lowstands 

from oldest to youngest is as follows: (1) an Early /Middle 

Cambrian transition; (2) a transition between the Late 

Cambrian Sakian and Aksayan ages (Ivshinagnostus 

ivshini and Pseudagnostus pseudangustulobus trilobite 

zones) in southern Kazakhstan, which correlates with the 

Elvinia/Taenicephalus trilobite zone transition in North 

America; (3) a Late Cambrian Eoconodontus conodont 

zone (Batyrbayan/late Trempealeauan); and (4) a Lange 

Ranch eustatic event near the Cambrian/Ordovician 

boundary (Cordylodus proavus conodont zone). 

Events recognized in western North America and 

southern Kazakhstan that we interpret to be related to 

eustasy are coeval with other sedimentologic and faunal 

evidence of Late Cambrian and Early Ordovician sealevel changes in Estonia, western Newfoundland, and the 

People's Republic of China. The corroborating evidence 

includes mass failure of carbonate platform margins, 

presence of solution surfaces in shallow-water carbonate 

settings, and disconformities in both low- and relatively 

high-paleolatitude sites. 

Play Analysis Methodologies for 

Petroleum Resource Assessment 

Robert A. Crovelli and Richard H. Salay 

The petroleum resource assessment studies of the 

U.S. Geological Survey (USGS) have resulted in a wide 

variety of analyses, geologic models, quantitative 

methods, and computer programs. The type of analysis 

refers to the basic geologic assessment unit, for example, 

province, basin, or play. The geologic model consists of 

the geologic assumptions and mathematical description 

of the assessment approach, for example, reservoir 

engineering, volumetric yield, field size, or direct 

assessment. The quantitative method is the type of 

probabilistic methodology that is mathematically derived 

from the geologic model, for example, Monte Carlo 
simulation or analytic probability theory. Computer 

programs are written on the basis of the probabilistic 

methodology. 

During recent years, the USGS has made major 

strides in designing and developing play analysis and 

analytic probabilistic methodology with a variety of 

geologic models. Play analysis is a general approach 

using various geologic models and probabilistic methods 

for analyzing a geologic play. In applying play analysis, a 

petroleum assessment area is first partitioned into 

geologic plays, and then the individual plays are analyzed. 

The individual play estimates of oil and gas are 

aggregated, respectively, in order to estimate the 

petroleum potential of the entire assessment area. 

A probabilistic system of petroleum resource 

assessment for play analysis has been designed to meet 

the following requirements: (1) includes a variety of 

geologic models, (2) uses an analytic methodology 

instead of Monte Carlo simulation, (3) can aggregate 

estimates from many areas that have been assessed by 

different geologic models, and (4) runs quickly on a 

microcomputer. The geologic models consist of four 

basic types: reservoir engineering, volumetric yield, field 

size, and direct assessment -listed in order of decreasing 

amount of geologic information required. The reservoirengineering model, the most data-intensive, was used in 

the three recent studies by the USGS described herein. 

These three assessments are followed by a National 

assessment using a field-size model. 

Arctic National Wildlife Refuge Assessment 

The Arctic National Wildlife Refuge (ANWR) 

study completed in 1987 assessed in-place oil and gas 

resources of geologic plays in the North Slope of Alaska 

using a reservoir-engineering model. An analytic 

methodology using probability theory was developed, and 

a package consisting of six computer programs was 

created and called Fast Appraisal System for Petroleum, 

Reservoir Engineering (FASPRE). 

Hungary Assessment 

The Hungary assessment of the Bekes basin 

generalized the reservoir-engineering model and the 

aggregation model that were used in the 1987 ANWR 

study, which was site-specific to the North Slope of 

Alaska. The modifications required that the system 

produce output in metric units and run on an IBMPC-XT compatible computer. 

The analytic probabilistic methodology was 

adapted from the 1987 ANWR study by replacing the 

site-specific reservoir-engineering equations with general 

equations and parameters. The universal metric version 

of the play analysis software was called F ASPUM. 

19 

Tight Gas Sands Assessment 

The Tight Gas Sands study assessed lowpermeability gas resources of the Upper Cretaceous 

Mesaverde Group in the Piceance basin of western 

Colorado. The system used in this study (FASPUE) was 

adapted from FASPUM by conversion to English (inchpound) units. An entire play area is treated as a single gas 

accumulation. 

National Assessment 

The USGS recently completed its first petroleum 

resource appraisal of the entire United States using the 

field-size model of play analysis. An analytic probabilistic 

methodology was developed based upon the field-size 

model and a new risk structure. A computer package 

called Fast Appraisal System for Petroleum, Field Size 

(F ASPF) was written for play analysis, subplay analysis, 

economic analysis, and aggregation analysis. Subplay 

analysis includes estimation of resources on State 

offshore areas. Economic analysis truncates field-size 

distributions using a minimum economic cut-off value. 

Aggregations of individual play and subplay estimates of 

oil and gas are made at the provincial, regional, and 

national levels. 

Origin and Distribution of Inorganic 

Elements in the Wyodak-Anderson Coal 

Bed, Powder River Basin, Wyoming 

S.S. Crowley, R.W. Stanton, 

D.M. Triplehorn, and L.F. Ruppert 

The distribution of selected major, minor, and 

trace elements indicates detrital, volcanic, and peatforming origins for inorganic elements in two cores of the 

Wyodak-Anderson coal bed of the Fort Union 

Formation (Paleocene) of the Powder River Basin, 

Wyoming. Of particular interest are altered volcanic-ash 

layers, which may be useful in correlating thick coal beds 

of the Powder River Basin. The ash layers in these cores 

are not partings that can be easily observed in outcrop 

sections or core, and although the layers can be observed 

as sharp peaks in geophysical logs, the peaks are easily 

confused with those for detrital partings and pyrite. For 

these reasons, we found in this study that the volcanic ash 

layers are best identified using geochemical and 

mineralogical methods. 

The coal bed recovered from corehole A, located 

80 km southeast of Gillette, is 22 m thick and was divided 

into 29 separate interval-samples selected on the basis of 
Sample 

Intervals 

Sample 

Intervals 

250 5000 5000 

rpm! ~ lppml 

2% 

1---{ 

250 5000 5000 Feet M 

~ 'ppm' ~ 

2% 

1---1 0 0 

A 

CLUSTERS 

COREA ~ p:·:·:·:·:·) r--1 ...... L___j 

1&2 3 4 

COREE 

1 n&m IV 

~ 

~ 

rock 

20 

30 

40 

50 

60 

70 

5 

20 

5 

Figure 1 (Crowley). Chemical profiles of two series of samples of cores A and E from the Wyodak-Anderson coal bed. 

megascopic lithologies and X-ray radiography (fig. 1 ). 

The coal bed recovered in corehole E, located 10 km 

north of Gillette, is 36 m thick and was divided into 38 

separate interval-samples. 

Samples in each core were grouped by their 

elemental compositions (30 elements) using cluster 

analysis. All data used in the analysis were reported on 

(or calculated to) an ash basis and standardized. In core 

A, based on the analysis, four major sample clusters were 

evident: (1) coal samples nearest the roof rock, (2) 

samples from partings and the coal samples nearest the 

floor rock, (3) coal samples about 5 m above the base of 

the coal bed, and ( 4) coal samples throughout the rest of 

the coal bed (fig. 1). 

20 

The following elements are concentrated in 

samples from cluster 3, compared to other samples: Nb, 

Zr, Sr, Ba, and P20s. Previous studies, such as a 1988 

study by D.A. Spears and others, reported that in 

volcanically derived tonsteins, Sr, P20s, and Ba are found 

in aluminum phosphate minerals. From binocular 

microscope and SEM examination, the cluster 3 layers 

were found to contain two separate suites of minerals: (1) 

the beta form of quartz, euhedral zircons, and (2) several 

authigenic minerals: calcite, pyrite, kaolinite, quartz, 

anatase, barite, and an aluminum phosphate ( crandallite?). 

Based on the cluster analysis, four sample clusters 

were evident in core E: (I) samples from partings and 
coaly samples nearest roof and floor rock, (II) coal 

samples from intervals 1.5 to 10.4 m above the base of 

the coal bed, (III) one sample about 2.4 m above the base 

of the coal bed, and (IV) samples throughout the rest of 

the coal bed (fig. 1 ). 

We infer that the chemical compositions of 

samples in clusters 1 and 2 of core A and cluster I of core 

E were influenced by detrital processes, because of the 

proximity of the samples to detrital material. The 

chemical compositions of the samples in cluster 4 of core 

A and cluster IV of core E are inferred to be derived 

principally from the peat-forming plants. 

On the basis of the distribution of elements and 

mineralogy of core A, we suggest that layers in the cluster 

3 samples of core A originated as volcanic ash. The glass 

and less stable minerals probably altered relatively 

quickly, and the morphology of the resistate minerals 

(quartz and zircon) remained relatively unchanged. 

Although the analysis of inorganic elements in core E is 

preliminary, the distribution of elements suggests that 

certain layers in coal samples (clusters II and III) may 

also have originated as volcanic ash that underwent a 

large degree of alteration. Work is in progress to examine 

the mineralogy of the possible volcanic ash layers in this 

core. 

Enhanced Upwelling and Organic 

Productivity During the Late Quaternary 

in the Northeastern Pacific Ocean 

Walter E. Dean and James V. Gardner 

The present upper water mass of the northeastern 

Pacific Ocean off California and Oregon has a welldeveloped oxygen-minimum zone (OMZ) between 600 

and 1,000 m wherein concentrations of dissolved oxygen 

are less than 0.5 mL/L. The OMZ is caused by 

decomposition of large seasonal stocks of plankton 

supported by high concentrations of nutrients within the 

California-Current upwelling system. Even at such low 

concentrations of dissolved oxygen, benthic burrowing 

organisms are abundant enough to destroy millimeterscale seasonal laminations (varves), and surface and 

near-surface sediments are thoroughly bioturbated. 

However, laminated and microbioturbated sediments are 

preserved in the upper Pleistocene and lower Holocene 

sections of cores collected on the continental slope at 

water depths within the present OMZ (fig. 1, p. 22). 

Laminated sediments are most prominent in cores 

collected in water depths of about 700 m, and are present 

laterally from at least as far north as the Klamath River 

area, and as far south as Point Sur. Detailed analyses of 

the laminae, and correlation with seasonal components 

21 

of pelagic "snow" collected in sediment traps 

demonstrate that the laminae are indeed varves. These 

varved sediments contain more abundant lipid-rich 

"sapropelic" (Type II) organic matter than the bioturbated and oxidized upper Holocene sediments deposited 

within the last 5,000 years. The decrease in Type II 

organic matter after about 5 ka might be due to a change 

in either source or degree of preservation of the organic 

matter. However, because the stable-carbon isotopic 

composition of the organic carbon does not change with 

time, we can eliminate a change of source as a possibility. 

The organic-carbon-rich, laminated sediments also 

contain higher concentrations of sulfide-sulfur, relative 

to the bioturbated sediments, indicating a higher rate of 

sulfate reduction due to the presence of more "reactive" 

organic matter. Concentrations of several trace elements, 

especially Cr, Cu, Ni, V, and Zn, also are enriched in the 

laminated sediments. The presence of carbon-, sulfur-, 

and metal-rich sediments, as well as the lack of bioturbation, all suggest that the OMZ in the northeastern 

Pacific Ocean was more intense prior to 5 ka. 

The intensity of an OMZ may be partly related to 

the rate of advection of dissolved oxygen, but is mainly 

controlled by the biological oxygen demand imposed on 

the water column that is modulated by the rate of 

primary productivity. We infer, therefore, that prior to 

about 5 ka, productivity of the North Pacific Ocean off 

California and Oregon was greater than today. One 

possibility is that upwelled intermediate to deep water 

contained higher concentrations of dissolved nutrients 

(mainly N and P). Another possibility is that the 

California-Current upwelling system was more intense 

and persistent for a longer season (perhaps 6 months or 

longer) during the late Pleistocene. This second 

possibility further implies that the summer North Pacific 

high-pressure system that drives the California Current 

must have been more persistent in order to supply more 

nutrients to support increased productivity. This change 

in atmospheric circulation would have resulted in more 

intense upwelling along the west-coast margin, a longer 

period of supply of high nutrient concentrations, a longer 

period of sustained primary productivity, and a longer 

season of oxygen depletion in the water column, thereby 

preserving varves on the seafloor. 

The USGS Evolution of Sedimentary 

Basins Program 

Walter E. Dean, Samuel Y. Johnson, and 

Thomas D. Fouch 

The USGS Evolution of Sedimentary Basins (ESB) 

Program was created to provide a mechanism for 
78 

79 

80 

81 

82 

83 

84 en 

a: 

w 

li:i 85 :::1! 

F 

z 

w 

u 86 ~ 

w 

a: 

0 

u 87 

~ 

:I: 

b:: 86 w 

0 

89 

90 

91 

92 

93 

94 

Figure 1 (Dean and Gardner). Typical laminated (varved) and microbioturbated 

Pleistocene-Holocene sediments from a core taken on the continental slope off northern 

California. 

22 
conducting multidisciplinary, integrated geologic 

research in energy-rich sedimentary basins. Coordinated 

research topics include geophysics, structural geology 

~nd tectonics, physical stratigraphy, biostratigraphy, sedImentology, paleogeography, paleoclimatology, petrology 

and diagenesis, geochemistry, heat flow and thermal 

maturity, paleohydrology, and basin modeling. Data are 

collected from outcrops, borehole logs and cores, and 

geophysical surveys (magnetics, gravity, seismic 

reflection and refraction, and remote sensing). Results of 

regional and topical basin research are being published 

as reports, maps, and charts that provide data 

summaries, interpretation, and synthesis. 

The ESB studies concentrate on basic geologic 

research and thus are distinct from the commodityfocused USGS energy research programs (oil and gas, 

coal, uranium, and oil shale). In practice, however, ESB 

and commodity-program research are closely 

coordinated in order to maximize impact for resource 

exploration, development, and assessment. ESB studies 

generate and place in the public domain important 

information products and data bases used by Federal, 

State, and local governments to assess and predict energy 

and metal resources and potential, as well as geologic 

hazards. Private energy companies use ESB data and 

products to develop and test exploration strategies and to 

evaluate their own proprietary data bases. Similarly, 

academic researchers commonly utilize ESB framework 

studies in conducting their own basic or applied research. 

Reports of work in progress have been regularly provided 

to participants in ESB-sponsored basin workshops. 

The ESB Program began in 1985 with studies by 

multidisciplinary research teams of six energy-rich 

basins: (1) the North Slope basin, Alaska; (2) the Anadarko basin, Oklahoma; (3) the Powder River basin, 

Wyoming and Montana; (4) the San Juan Basin, New 

Mexico and Colorado; (5) the Uinta-Piceance basin, 

Utah and Colorado; and (6) the Central Appalachian 

basin, West Virginia, Virginia, Tennessee, and Kentucky. 

These initial six basin efforts are in their completion 

phase. A study of the Santa Maria basin, California, 

began in 1987 and will be completed in 1991. Five-year 

USGS-ESB studies of (1) the eastern Great Basin, Utah 

and Nevada; (2) the Paradox basin, Utah and Colorado; 

and (3) the Illinois Basin (in cooperation with the Illinois 

Indiana: and Kentucky State geological surveys) wer~ star.ted_m October 1989. ~study of Tertiary sedimentary 

basms m southwest Washmgton and northwest Oregon is 

slated to begin in 1991. Studies of one or more Laramide 

basins of western Wyoming will be initiated in 1991 or 

1992. Pilot studies of the Washington-Oregon and 

Wyoming basins are being conducted in FY1990. 

23 

Uranium Favorability in the Chadron 

Formation, Southeastern Wyoming and 

Northwestern Nebraska 

K.A. Dickinson and P.L. Hansley 

The Chadron Formation of the Oligocene White 

River Group is the host rock of the Crow Butte uranium 

deposit (at least 30 million pounds of U 3 0 8 ) located near 

Crawford in northwestern Nebraska. The uraniummineralized rock is present in a basal medium- to coarsegrained arkosic sandstone member of the otherwise 

clayey Chadron. Locally this basal sandstone member is 

called the Chadron sandstone. It was deposited in fluvial 

channels that in most areas are incised into the 

underlying Cretaceous Pierre Shale. 

The Chadron Formation contains abundant rhyolitic ash that is partially altered to smectite and silica 

minerals. Uranium was probably released during this 

alteration. The relatively permeable channel sands 

appear to have served as conduits for the flow of the 

uranium-bearing ground water. The impermeability of 

underlying shale aided in confining ground water flow to 

the Chadron sandstone. The predominant uranium 

mineral is cryptocrystalline coffinite, which is 

concentrated along the margins of the channels with 

closely associated pyrite and marcasite. Corrosion 

textures of the pyrite suggest that oxidation resulted in 

reduction and precipitation of the uranium. Oxidized 

rock is confined to the center of the channel where the 

flow of oxidizing ground water was greatest, whereas the 

reduced rock is confined to the channel margins. Organic 

material deposited in the channel sands probably aided in 

forming the reducing environments, but little of that 

material is now present. Sulfides introduced from the 

underlying black shale of the Pierre may also have 

provided a reductant. 

The Chadron is favorable for uranium in areas 

other than the Crow Butte area, but it is favorable only 

where the basal sandstone member is present. The 

Chadron sandstone extends from areas northwest of the 

Hartville uplift near Douglas, Wyoming northeast, east, 

and south into northwestern Nebraska where the Crow 

Butte uranium deposit is located. Where the sandstone is 

thickest, the volume of uraniferous ground water flowing 

through the unit was potentially greater and favorability 

for uranium deposits is correspondingly increased. The 

maximum thickness of the Chadron sandstone is more 

than 280 feet in Nebraska in the vicinity of the Crow 

Butte deposit, but in Wyoming its thickness is much less, 

exceeding 100 feet in only a few areas. 
Figure 1 (Dillon). Study area, showing GLORIA sidescan survey location. Dotted line indicates location of profile shown in 

figure 2. 

Structural Segmentation in an Active 

Submarine Tectonic Accretionary Wedge, 

as Disclosed by GLORIA Sidescan Sonar 

and Multichannel Seismic Profiling, 

Caribbean Plate Boundary North of Haiti 

William P. Dillon, James A. Austin, Kathryn M. 

Scanlon, N. Terence Edgar, 

Lindsay Parson, and Gordon E. Ness 

The insular margin off the northwestern coast of 

Hispaniola (Haiti and the western Dominican Republic) 

occupies a region of strongly oblique collision of the 

Caribbean and North American plates that results from 

the general trajectories of the plates and the presence of 

a restraining bend on the Caribbean plate boundary. The 

study area (fig. 1) is the insular slope, which is shown by 

profiles to be a tectonic accretionary wedge (fig. 2), 

created by folding and thrusting of Hispaniola Basin 

strata against the backstop formed by the island of 

24 

Hispaniola. The structure of the slope indicates only the 

effects of collision, with no evidence of transcurrent 

motion. The regional seismicity pattern suggests that the 

plate boundary actually is situated south of the insular 

slope, near the present coastline, and therefore that the 

tectonic accretionary wedge is situated on North 

American plate basement. 

Bathymetry, GLORIA sidescan-sonar images, and 

seismic-reflection profiles demonstrate that the insular 

slope and underlying wedge are characterized by two 

morphological/structural styles that occur in three 

distinct and rather abruptly bounded compartments 

along the insular slope. In the central compartment, (1) 

the insular slope dips gently (about 4°); (2) the average 

slope profile is planar to concave but marked by broad 

fold ridges; (3) internal structure consists of broad anticlines (wavelength about 4.5 km) separated by thrust 

faults; and ( 4) the structural contact of slope to basin 

strata is gradational. In contrast, in the compartments to 

the east and west, (1) the insular slope dips steeply 

(9°-16°); (2) the slope profile is convex; (3) internal 
N 

Ul 

N TIME ALONG TRACK (HOURS) S - 1800 1600 1400 0 tH 

w 

~ 

2~ _J 

w 

4~ 0::: ~- ~ 

VE. = 3.25 

6~ 5 

I 

8~ ~ 

Figure 2 (Dillon). Seismic profile across the central compartment. V.E., vertical exaggeration. 
structure appears chaotic in seismic reflection profiles; 

and ( 4) the toe of the slope forms an abrupt structural 

front against Hispaniola Basin strata. 

The geologic settings of the two slope types seem 

quite similar. The interplate motions should be 

approximately the same along this rather straight section 

of the plate boundary, and the sedimentary strata 

entering the tectonic accretionary wedge should be 

identical, because they are derived from the same small 

turbidite basin. There is no obvious change in the backstop (Hispaniola). Inasmuch as these factors appear to 

remain the same, why are the slopes in the two morphological/structural styles so different? Why are the internal 

structural styles so different? 

Tectonic accretionary wedges are comparable to 

the pile of snow in front of a moving snowplow; that is, as 

long as conditions remain constant, the snow will 

maintain a constant slope in front of the plow. In a 

tectonic accretionary wedge, the angle between the 

sediment surface and the decollement (known as the 

critical taper) is modeled as a balance between the 

internal strength of the wedge against the forces of the 

compressional push (from Hispaniola), the basal 

frictional resistance (at the decollement), gravitational 

body force (tendency of the slope to spread out flat under 

the influence of gravity), and water pressure (in this 

submarine wedge). Although some of these factors might 

change and thus affect the angle of critical taper, we 

would not expect such abrupt changes in such a small 

area, and see no evidence for them. We suggest that the 

critical taper is likely to remain the same across the area 

and that the changes in slope merely reflect changes in 

dip of the decollement. If critical taper in the wedge is 

comparable to that of other wedges reported, it is less 

than 10°. Such an angle would cause the decollement to 

rise toward Hispaniola in locations where sea-floor slope 

is steepest, and space requirements would dictate a 

complicating structure, such as a duplex. The difference 

in internal structure may result from the difference in dip 

of the sea floor between the two styles. Weaker 

sediments are more easily folded, and sediment strength 

is increased by overburden loading. Therefore, the 

steeper slopes might result in much narrower zones of 

relatively weak sediment that is appropriate for folding 

(thickening occurs 3.6 times faster on crossing a slope of 

14° than at 4°). 

This study shows that, in the setting of a tectonic 

accretionary wedge, structural styles can change very 

rapidly along the structural trend, so that zones that 

might present petroleum traps (broad folds of turbidite 

sediments) can terminate abruptly against regions of 

intense faulting and crumpling. 

26 

Predictive and Actual Results from 2,500 

Wildcat Wells, Offshore Gulf of Mexico 

L.J. Drew and J.H. Schuenemeyer 

The accuracy of a forecast made in 1980, of the 

number and sizes of oil and gas fields expected to be 

discovered in the Miocene-Pliocene and Pleistocene 

trends in the offshore Gulf of Mexico, was determined by 

comparing the predicted and actual results from the 

drilling of 1,832 wildcat wells in the Miocene-Pliocene 

trend and 682 wildcat wells in the Pleistocene trend 

during the 1977-85 time period. This forecast was made 

using a two-stage procedure comprising both a discovery 

process model and the concept of economic truncation. 

A modified version of the Arps-Roberts discovery 

process model estimated the number of larger fields 

remaining to be discovered in each field size class 

(untruncated portion of the field size distribution). A 

geometric multiplier of the log geometric distribution 

allowed estimation of the number of fields remaining to 

be discovered in the truncated portion of the distribution 

(to the left of the mode) down to fields as small as 

729,000 barrels of oil equivalent. This assessment of the 

undiscovered oil and gas resources was in turn used, in a 

1982 report by Drew, Schuenemeyer, and W.J. Bawiec, 

as a basis to forecast the number and sizes of the fields 

that would be discovered in the future. 

During the 1977-85 period, 280 oil and gas fields 

were discovered in the Miocene-Pliocene trend, each 

containing more than 729,000 barrels of oil equivalent. 

Collectively, these fields contain 17.0 trillion cubic feet of 

natural gas and 542 million barrels of crude oil and 

condensate (3.38 billion barrels of oil equivalent) as 

viewed from a 1988 reserve estimation basis. The 85 

fields discovered during the same time period in the 

Pleistocene trend contained 4.8 trillion cubic feet of 

natural gas and 240.1 million barrels of crude oil and 

condensate (1.04 billion barrels of oil equivalent). 

The forecast made in 1980 for the period 1977-85 

for the Miocene-Pliocene trend estimated that 222 fields 

would be discovered, containing 1.79 billion barrels of oil 

equivalent. This is an underestimate of 1.59 billion 

barrels of oil equivalent in this trend ( 47 percent low). 

The forecast for the same period in the Pleistocene trend 

stated that 79 fields would be discovered containing 713.2 

million barrels of oil equivalent. Actually, 4.8 trillion 

cubic feet of natural gas and 241 million barrels of crude 

oil and condensate were discovered, or 1.04 billion 

barrels of oil equivalent (30 percent low) as viewed from 

a 1988 reserve estimation basis. 

This underestimation of the amounts of oil and gas 

discovered in both the Miocene-Pliocene and the Pleistocene trends during the 1977-85 period can for the most 
part be attributed to the field growth phenomenon. The 

field size data used to calibrate the discovery process 

model for the 1980 forecast were taken from the FRRE 

file, maintained at that time by the U.S. Geological 

Survey, and now maintained by Minerals Management 

Service. These estimates were based on engineering 

calculations without complete data on reservoir area or 

numbers of reservoirs or quality of the pays; and 

statistical growth factors were not applied to estimate the 

contribution to field growth through the process of 

extensions and revisions. For example, as a group the 

reserves in the 293 fields upon which the 1980 forecast 

was based, that is, fields discovered in the MiocenePliocene trend between 1946 and 1976, grew 18.7 Tcf of 

natural gas and 1.57 billion barrels of crude oil and 

condensate through the extension and revision processes 

between 1980 and 1988. The parallel growth in the 

Pleistocene trend was 7.2 Tcf of natural gas and 698 

million barrels of crude oil and condensate. The growth 

in reserves of the oil and gas fields discovered before 

1976 in both geologic trends during the 1980--88 period is 

then of the same numerical order as the volume of oil 

and gas discovered during the same period as viewed 

from the end of the time period. This result makes it 

clear, as suggested in a 1985 report by K.C. Manger, E.H. 

Vidas, and T. Woods, that a correction for field growth 

must be calculated and added to those oil and gas fields 

used to assess the size and number of undiscovered fields 

and to forecast future discovery rates. This has been done 

for both the Miocene-Pliocene and the Pleistocene 

trends. 

Deep Oil and Gas Wells and Reservoirs 

in the United States from the Well History 

Control System and Petroleum Data 

System 

T.S. Dyman, D.T. Nielsen, R.C. Obuch, J.K. 

Baird, and R.A. Wise 

Deep wells and hydrocarbon production are widely 

distributed in the U.S. in rocks of various ages and 

lithologies. Sixteen thousand six-hundred fifty wells have 

been drilled deeper than 15,000 ft in the U.S. since the 

first deep well was drilled in 1920, according to 

Petroleum Information Corporation's Well History 

Control System (WHCS) as of February 1988. Of these 

16,650 deep wells, 8,705 were completed as producing 

wells that could be producing oil and (or) gas at any 

depth (above or below 15,000 ft). Nearly as many gas 

wells exist (6,347) as dry holes (7,090); gas wells are 

three times more abundant than oil wells (2,181 ). In the 

WHCS file, 1,442 wells have a total depth greater than 

20,000 ft. 

27 

Of these 16,650 deep wells, 7,251 were drilled in 

the offshore region of Louisiana. Of the 2,860 deep wells 

in the Midcontinent region, 2,211 were drilled in the 

Anadarko basin and 354 in the Ardmore basin. Of the 

841 deep wells in the Rocky Mountain region, 175 are in 

the Uinta basin, 136 in the Wyoming thrust belt, 113 in 

the Green River basin, and 100 in the Wind River basin. 

Of the 3,547 deep wells in Mississippi, Alabama, and 

Florida, 1,876 were drilled in the Cretaceous-Jurassic 

trend; and 1,157 wells were drilled in the Gulf basin. A 

total of 19 deep wells have been drilled in the 

Appalachian, Michigan, and Illinois basins. 

In the WHCS file, 2,981 producing wells drilled 

deeper than 15,000 ft have a formation at total depth 

equal to the producing formation. These wells represent 

a minumum number of those wells that are actually 

classed as producing oil and gas deeper than 15,000 ft; 

they are referred to as deep-producing wells and form the 

basis for statements made in the following discussion. 

The ratio of gas-producing deep wells to total producing 

deep wells increases with increasing total depth of well. 

The gas-producing proportion of total deep-producing 

wells increases from a consistent 72 percent in the 

15,000-ft range to 90 percent in the 19,000-ft range. In 

the Rocky Mountain region, deep gas-producing wells 

account for 34 percent of the total deep-producing wells 

(265 total wells, 91 gas wells). The Uinta and Powder 

River basins are oil-rich below 15,000 ft whereas the 

Green River, Wind River, Washakie, and Bighorn basins 

and Wyoming thrust belt are predominantly gas-rich. 

Only eight wells classed as producing from 

reservoirs deeper than 15,000 ft were completed before 

1960, all of which were reported as gas producers. The 

first three wells to produce gas deeper than 20,000 ft 

were completed in 1967. The two deepest hydrocarbonproducing wells (producing deeper than 26,000 ft) were 

completed in 1977 and 1979. Deep gas-producing wells 

account for 70 percent of the total deep-producing wells 

completed during 1970 through 1975 and more than 80 

percent completed during the 1976--87 period. For all 

years together, more than 90 percent of the wells that are 

classed as producers below 20,000 ft are producing gas. 

Seventy-five percent of the oil wells completed 

deeper than 15,000 ft produce from clastic rocks ( 467 

wells, 7.6 million drilled ft). The greatest depths to clastic 

reservoirs occur in the New Mexico part of the Permian 

basin (average= 18,243 ft). In Utah, 136 deep-producing 

wells (more than 2 million drilled ft) were completed in 

clastic reservoirs. Three hundred sixty-six deep oil wells 

produce from Tertiary rocks; of these 168 produce from 

the Miocene in the Gulf Coast region and 134 from the 

Paleocene Wasatch Formation in the Rocky Mountain 

region. One hundred twenty-five deep-producing wells 

are Jurassic oil producers; 92 of these produce from the 

Smackover Formation. 
More than 75 percent of the deep wells completed 

as gas wells have produced from clastic rocks (1,740 

wells, >29 million drilled ft). The Anadarko basin and 

the Rocky Mountain region produce deep gas primarily 

from clastic reservoirs (352 wells, 5.6 million drilled ft). 

In Texas, 55 percent of the deep-producing wells (377), 

accounting more than 7 million drilled ft, were 

completed as producing from carbonate rocks; most of 

these are producing from the Ordovician Ellenburger 

Group in the Permian basin. Texas and Louisiana have 

more deep wells which produce from carbonate rocks 

than from clastic rocks. Ninety-nine deep-producing 

wells produce from carbonate rocks· in the Jurassic 

Smackover Formation in Alabama, Mississippi, and 

Florida. 

Approximately 7 billion barrels of oil and 50 trillion 

fe (TCF) of nonassociated gas have been produced from 

2,007 deep reservoirs through 1985 according to the 

Dwight's Energy Data Petroleum Data System (PDS). 

Deep gas accounts for about 8 percent of the U.S. 

cumulative gas production (698 TCF), and deep oil 

accounts for about 5 percent of the U.S. cumulative oil 

production (143 billion barrels). The Midcontinent, 

Texas, and Gulf Coast regions, with 1,900 deep 

reservoirs, account for 95 percent of the cumulative deep 

oil and gas production in the U.S. 

Cumulative nonassociated gas production for deep 

reservoirs discovered prior to 1970 equals 9.2 TCF, 

which is 18 percent of the cumulative deep gas 

production in the U.S. Thirty-four of the 260 active deep 

reservoirs in the PDS file were discovered prior to 1970. 

The oldest reservoirs were discovered in the Permian 

basin and Gulf Coast region. 

New Methodologies for Assessment of 

U.S. Oil-Shale Resources 

John R. Dyni 

During the past 20 years, the U.S. Geological 

Survey has developed a large database of Fischer assays 

as well as a collection of drill cores and crushed samples 

of oil shale for assessment of oil-shale resources of the 

United States. Assessment of these resources for future 

energy needs will require additional analyses to better 

characterize the deposits with respect to: types and 

maturity of organic matter, amounts of oil and gas 

obtainable by pyrolysis, amounts of residual carbon 

recoverable as thermal energy, potential mineral byproducts, and oil-shale components that may impact the 

environment. Such information will be vital in order to 

evaluate individual oil-shale deposits for recovery of oil 

and gas by conventional technologies as well as by newer 

processes such as hydroretorting and downhole 

gasification. 

28 

Among the important analytical methods available 

for resource assessment of oil shale are Rock-Eval, 

ultraviolet fluorescence microscopy, 13C nuclear 

magnetic resonance, hydro retorting assay, pyrolysis 

fluorescence, and X-ray analysis. These methods, in 

combination with improving the Fischer assay procedure, 

can provide more complete information about (1) kind 

and degree of thermal maturity of organic matter, as well 

as (2) types of organic matter that respond best to 

different methods of extracting oil, gas, and thermal 

energy from oil shale. Application of some of these 

methods to evaluating oil-shale deposits should be of 

value not only to economic geologists, but also to mining 

and process engineers who will be developing these 

resources. 

Once a Menace, Now a Burgeoning 

Source of Energy-Coal-Bed Methane in 

the Warrior and San Juan Basins 

James E. Fassett 

During the 1980's, coal-bed methane has come to 

be recognized as an enormous energy resource. As much 

as 850 Tcf (trillion cubic feet) of coal-bed methane is 

estimated to be trapped in coal-bearing basins of the 

United States. This estimate is more than four times 

larger than present estimates of natural gas reserves in 

conventional reservoirs. Natural gas produced from coal 

beds is essentially methane and can be added to naturalgas pipelines without any special treatment. The gas is 

generated first biogenically and later thermogenically 

during the coal-forming process and is stored in the 

micropore and macropore porosity of the coal beds. 

Coal-bed methane is adsorbed on and (or) absorbed in 

the coal microstructure. Typical recovery entails 

pumping water out of the macropore system (cleats), 

thereby lowering the hydrostatic pressure on the coal-bed 

reservoir and allowing the gas to desorb from the coal 

micropore system. Production problems include 

controlling coal-fines produced with the water and gas 

and disposing of produced water in areas where surface 

disposal is environmentally unacceptable. Coal-bed 

methane wells typically demonstrate an increase in gas 

production and a decrease in water production over time; 

they are thus characterized by incline production curves 

in contrast to the customary decline curves associated 

with gas production from conventional reservoirs. 

The Warrior Basin of Alabama and the San Juan 

Basin of New Mexico and Colorado are the only largescale, commercial producers of coal-bed methane in the 

United States. Warrior Basin coals are in the Pottsville 

Formation of Pennsylvanian age, are usually less than 5 ft 
(1.5 m) thick, have ranks ranging from high-volatile to 

low-volatile bituminous, and are present under a large 

area at depths less than 3,000 ft (900 m). The Alabama 

part of the Warrior Basin contains 54 billion tons of coal 

that is estimated to contain 39 Tcf of gas (1.1 trillion m3 ), 

of which 15 Tcf (0.4 trillion m3

) or more is considered 

recoverable. Through June 1988, the Warrior Basin has 

produced 60 Bcf (billion cubic feet) (1.7 billion m3

) of 

coal-bed methane. 

Nearly 95 percent of San Juan Basin coal is in the 

Upper Cretaceous Fruitland Formation. Fruitland coal 

beds range from 1 or 2ft (0.3-0.6 m) to 40-50 ft (12-15 

m) thick; total Fruitland coal thickness exceeds 70ft (21 

m) in the northern part of the basin. Fruitland coals 

range in rank from subbituminous to medium-volatile 

bituminous. Fruitland coals are less than 4,000 ft (1,200 

m) deep throughout most of the basin. The Fruitland 

contains more than 200 billion tons of coal that is 

estimated to hold 50 Tcf of gas (1.4 trillion m3 ). It has 

been estimated that 25 Tcf (0.7 trillion m3

) of this gas is 

recoverable. Through 1987, the San Juan Basin has 

produced 85 Bcf (2.4 billion m3 ) of coal-bed gas. 

The immediate future of coal-bed methane is 

somewhat unclear, largely because of as-yet-unmade 

political decisions regarding energy use in the United 

States. For example, if laws were passed creating 

incentives to use natural gas instead of more polluting 

fuels to create electrical energy, the economics of gas 

production could literally change overnight. At the 

present time, coal-bed methane receives a gas-tax credit 

that is clearly helping to encourage the accelerating 

development of this exciting new resource. Will the 

scheduled expiration of this gas-tax credit at the end of 

1990 put a damper on the coal-bed methane 

development activity? Certainly, some of the larger coalbed methane gas wells of the San Juan Basin would be 

commercial, with or without the gas-tax credit. 

Whatever is decided politically in the near future, 

however, will have little bearing on the ultimate future of 

coal-bed methane; it is an enormous resource that is 

waiting for its time to come and it will be used, as present 

supplies of generally-less-expensive energy resources are 

used up, making coal-bed methane more competitive in 

the market place. 

New Developments in Uranium 

Endowment Assessment in the 

United States 

Warren I. Finch, Charles T. Pierson, Richard B. 

McCammon, James K. Otten, Hoyt B. Sutphin, 

and Karen J. Wenrich 

Responsibility for assessing the uranium 

endowment in the United States was returned to the U.S. 

29 

Figure 1 (Finch). Index map showing the location of the 

NTMS 1°X2° quadrangles mentioned in this report. 1, Cedar 

City; 2, Grand Canyon; 3, Marble Canyon; 4, Williams; 5, 

Flagstaff; 6, Prescott; 7, Holbrook; 8, St. John; 9, Sandpoint; 

10, Spokane; 11, Alliance; 12, Torrington; 13, New Castle; 14, 

Hot Springs. 

Geological Survey by the Memorandum of Understandingof1984 between the U.S. Department of Energy 

and the Department of the Interior. (Uranium 

endowment is the uranium estimated to occur in rock 

with a grade of at least 0.01 percent U30s. The economic 

portion of endowment is calculated using a higher grade 

cutoff, commonly 0.10 percent U30s.) Since that time 

the USGS has developed a new assessment method 

(outlined in a 1987 report by Finch and McCammon), 

which is a modification of the NURE (National Uranium 

Resource Evaluation) method. Two regions have been 

assessed using the new method, and a third is currently 

being assessed. 

The new method is called the "depositsize-frequency" (DSF) method and consists of a 

modification of the NURE uranium endowment (U) 

estimation equation, U =A•F•T•G, in which the factors 

F•T (F =fraction of area, A, that is favorable for 

endowment; T = tons of endowed rock per unit area) are 

replaced by a single factor. This factor is the summation 

of the estimates of the number of deposits of different 

deposit-size classes within the area being assessed, or, 

equivalently, the spatial density of deposits; hence, the 

name "deposit-size-frequency." The average grade (G) 

of the endowment is the same in both methods. The DSF 
method requires (1) that a deposit-size-frequency (a 

matrix of the lower limit, most likely, and upper limit of 

number of deposits in each size class) be established in a 

well-known to fairly well known area, called the control 

area, and (2) that the geologic factors that produced this 

frequency be determined. Using these requirements for a 

control area, the assessor estimates the size frequency of 

undiscovered deposits for the favorable area based on 

similarity to the control area. The probabilistic estimates 

of undiscovered uranium endowment are calculated 

using the computer program TENDOWG, published in a 

1988 study by McCammon and others. 

In 1987, the undiscovered uranium endowment 

was estimated for ''young organic-rich uranium deposits" 

in the Colville-Okanogan favorable area in the Sandpoint 

and Spokane NTMS 1 °X2° quadrangles, Washington and 

Idaho (fig. 1 ). These uranium deposits occur in surficial 

organic-rich fluvial, alluvial, and lacustrine sediments 

laid down in the past 15,000 years. The deposits average 

from 0.03 to about 0.10 percent U30s, and contained 

U30s ranges from a few hundred pounds to as much as 

a million pounds. The uranium endowment in the 

Colville-Okanogan favorable area is estimated to lie 

between about 6,750 and 122,000 short tons of contained 

U30s, and the mean (unconditional) undiscovered 

uranium endowment is 35,300 short tons U30s. 

In 1988, the undiscovered uranium endowment 

was estimated for the solution-collapse breccia pipes in 

the Grand Canyon region in the Grand Canyon, Marble 

Canyon, Williams, Flagstaff, Holbrook, St. Johns, and 

Prescott NTMS 1 oX 2° quadrangles in Arizona and the 

Cedar City quadrangle in Utah (fig.1). Solution-collapse 

breccia-pipe uranium deposits occur in pipes that formed 

as a result of solution collapse within the Mississippian 

Redwall Limestone and stoping of the overlying 

Pennsylvanian, Permian, and Triassic rocks (Wenrich 

and others, this volume). Most of the uranium deposits 

are high grade by U.S. standards, averaging between 0.43 

and 0.65 percent U30s. Typical deposits contain 125,000 

to 500,000 tons of ore, yielding 1,000,000-6,000,000 lb of 

U30s. The uranium endowment was estimated for 26 

favorable areas that total 16,728 mi2

• The mean 

(unconditional) uranium endowment totals about 

1,300,000 short tons U30s. This value is about eight 

times the total endowment of 158,000 tons estimated for 

these breccia pipes in a 1980 study, part of the U.S. 

Department of Energy NURE program. The larger 

USGS endowment value is due to three factors: (1) the 

DSF method allows for greater partitioning of input data 

and results in less biased (generally larger) estimates, (2) 

current knowledge of grade and tonnage of post-1979 

discovered deposits is significantly greater, and (3) 

understanding of the geology of the region has greatly 

improved. 

30 

During 1989, an assessment of undiscovered 

uranium endowment was initiated for the roll-type 

uranium deposits in the Oligocene Chadron Formation 

in the Alliance, Torrington, New Castle, and Hot Springs 

NTMS 1°X2° quadrangles, Nebraska, Wyoming, and 

South Dakota (fig. 1; Dickinson and Hansley, this 

volume). We expect to complete this assessment in 1990. 

New Information on the Nuwok Member 

of Sagavanirktok Formation; Implications 

for Petroleum Geology of the North Slope 

and Beaufort Sea-Evidence from Carter 

Creek, Arctic National Wildlife Refuge 

(ANWR), Alaska 

T.D. Fouch, E.M. Brouwers, D.H. McNeil, Louie 

Marincovich, Jr., K.J. Bird, and H. Rieck 

Examination of the Nuwok Member of the Sagavanirktok Formation has identified at least 220 m of 

Nuwok-like strata, a significant addition to the previously 

described 80 m assigned to the member. The beds are 

expo'sed on the north limb of the Marsh Creek anticline 

along Carter Creek, which is located about 160 km east 

of Prudhoe Bay and 0.8 km south of the Beaufort Sea (lat 

70° N.). Beds are deeply weathered and eroded, but 

where trenched, yield exposures sufficient for stratigraphic reconstruction, and for sedimentologic, paleomagnetic, and biostratigraphic sampling and analysis. 

The Nuwok at Carter Creek represents marine 

shelf and prodeltaic sedimentation and consists primarily 

oflithified and unconsolidated pebbly fine sands and silts. 

Upper parts of the Nuwok contain concretions, and 

medium- and coarse-grained sandy units. Lower strata of 

the Nuwok contain laminated to thin flat beds of siltstone, argillaceous claystone, and fine-grained sandstone, 

associated with ostracode and benthic foraminifers that 

suggest middle-shelf water depths. Abundant suspended 

siliceous pebbles ( dropstones?) and a high proportion of 

rafted plant material (fine organic debris, twigs, limbs, 

and mineralized and woody logs) express considerable 

terrestrial input. Some units contain pebbles, their long 

axes randomly aligned, suspended in a poorly sorted, very 

fine grained structureless matrix; these probably 

represent submarine debris flows. 

The section displays an overall upward-shoaling 

trend indicated by progressive upward coarsening of the 

overall sequence and of individual units, increasing 

thickness of bed sets and scale of crossbeds, 

concentrations of large log fragments upsection, and the 

appearance of inner-shelf mollusk and ostracode 

assemblages. Coarsest strata are best developed between 

95-105 m and 155-176 m above the base of the 
measured exposures; they include units several meters 

thick composed of prograding unconsolidated mediumand coarse-grained sand units in multiple cycles of offlapdownlap crossbed sets (some greater than 10 em thick) 

each mantled by clayey drapes (traction and suspension 

cycles). This association suggests periodic episodes of 

near-shore progradational sediment transport across a 

shallow (inner-shelf?) sea floor. 

The precise age of the Nuwok Member at Carter 

Creek is uncertain. Benthic fossil groups yield widely 

disparate ages. A prolific calcareous benthic foraminifer 

assemblage ranges through the entire Nuwok sequence. 

The ubiquitous occurrence of Turrilina alsatica, known 

from the western North Atlantic, the North Sea, and 

northwestern Europe, indicates a late Oligocene age; this 

age is supported by Sr 87/86 ages of 23.8--27.0 Ma from 

Nuwok foraminifers and mollusks. The foraminifer 

assemblage is diverse and abundant for a high-latitude 

site; absolute diversity is greater than 70 species, and 

specimen abundance is as high as 100 per gram. The 

fauna is dominated by Cibicidoides, Cribroelphidium, 

Elphidiella, M elonis, Nuttallides, Trifarina, Turri /ina, as 

well as miliodids, nodosarids, polymorphinids, and 

unilocular genera. A normal marine shelf environment is 

indicated. 

The Nuwok contains two distinct mollusk 

assemblages with mutually exclusive species: a lower 

Chesapecten nuwokensis zone, ranging from the base of 

the sequence to a concretionary unit at 95 to 105 m, and 

an upper Arctica carteriana zone, extending from 105 to 

300 m from the base. The mollusks are all Atlanticderived, indicating a pre-Bering Strait age ( > 3 Ma ). 

Generic level correlations and the evolutionary lineage of 

Chesapecten imply a maximum age of middle Miocene. 

Age arguments based on ostracodes are weaker, 

being based on the presence of extant species, correlation 

with global climatic trends, and genus-level comparison 

with lower latitude faunas. Two ostracode assemblages 

are recognized: the lower assemblage ranges from 60 to 

90 m above the base and includes warm-water genera 

(Cytheretta, Echinocythereis, Cytherelloidea); the upper 

assemblage, ranging from 90 to 245 m above the base, 

consists of temperate to warmer sub frigid genera (Rabilimis, Robertsonites, Cytheropteron, Paracyprideis ). Several 

taxa range throughout the section, but most species show 

stepwise disappearance believed related to changes in 

climate and water depth. Warm-water genera do not 

occur above 110 m, most dropping out just below a 

concretionary zone at 95 to 105 m. 

Paleomagnetic analysis indicates that the Nuwok 

strata have normal polarity from the base of the 

measured section to about 40 m, reversed polarity from 

the 40 to 180 m level m with several =10-m-thick 

sequences of normal polarity, one of which corresponds 

to the concretionary zone extending from 95 to 100 m; 

31 

and normal polarity from 180 to 190m. Lack of adequate 

exposures precludes collection of samples from 190 to 

300 m. Laboratory analysis indicates some magnetization 

is carried by secondary minerals. However, the presence 

of clearly defined polarity zones suggests that the mineralogic changes occurred shortly after deposition. 

Strata that are presumably partial age equivalents 

to the Nuwok (Oligocene and younger-based upon 

palynomorph interpretations) have been penetrated in 

drill holes west of Carter Creek near the Canning River, 

and in the Beaufort Sea north of Camden Bay. Excellent 

petroleum reservoir sandstone units were penetrated in 

these tests that may be represented by the thick innershelf progradational sand sequences exposed along 

Carter Creek. 

Sedimentology, Diagenesis, and 

Reservoir Character of Paleogene Fluvial 

and Lacustrine Rocks, Uinta 

Intermontane Basin, Utah-Evidence 

from the Altamont and Red Wash Fields 

T.D. Fouch, J.K. Pitman, J.B. Wesley, 

Adam Szantay, and F.G. Ethridge 

Examination of the Paleogene part of the oilbearing strata in the Uinta basin indicates that most 

reservoirs formed in an internally drained intermontane 

depositional system. Two major phases of lake 

development gave rise to deposition of sediments that 

became petroleum source and reservoir rocks, tar 

sandstone, thick sequences of evaporite units, oil shale, 

and local uraniferous beds. 

Lake sediments of the first phase of development 

(Maastrichtian to earliest Eocene) are typical of 

deposition in shallow water within the photic zone. Fossil 

mollusk species, gypsum beds, and subsurface units 

containing anhydrite indicate that alkaline lake water was 

relatively low in chlorides. Although permanent lakes 

existed, many were intermittent, and large areas were 

subject to long periods of subaerial exposure and soilforming processes. During the second phase of 

development in early Eocene to early Oligocene(?) time, 

a single large lake complex developed and reached its 

greatest areal and volumetric extent. The thickest fluvial 

and lacustrine sequence formed near Altamont field in 

front of the rising Uinta Mountains along the central 

segment of the axis of the subsiding Uinta basin. In this 

area, more than 3,000 m of Paleocene and Eocene 

lacustrine rock are preserved, and the strata contain 

more than 1,200 m of fine-grained kerogenous carbonate 

and mudstone units, including oil shale, that formed 

during the middle and late Eocene between 46 and 42 

Ma. 
The thickest and most widespread lake deposits of 

the second phase principally comprise chemical 

precipitates, including carbonate units and basincentered halite and sodium bicarbonate evaporite units, 

that formed from sulfate-depleted, saline, alkaline lake 

water in the clastic sediment-starved center of the 

hydrologic basin. The northern and western faultbounded margins of the basin are marked by synorogenic 

coarse conglomerate and conglomeratic sandstone units 

that extend from the mountain front into or near the lake. 

Rocks of the first phase of sedimentation produce 

oil and gas from deeply buried, overpressured, fractured 

reservoirs in the Altamont-Bluebell and Cedar Rim 

fields. Though overpressured strata exist locally, second 

phase rocks yield oil and gas primarily from normally 

pressured rocks at Altamont, Bluebell, Red Wash, Pariette Bench, River Bend, and Duchesne fields. 

Principal petroleum reservoir rocks are diagenetically altered fluvial channel, deltaic, and open lacustrine 

sandstones (including turbidites in Altamont) that 

formed near the lake margin, and nearshore lacustrine 

bars and beaches that apparently developed parallel with 

the northeastern margin of the lake in Utah. The 

channel-form bodies in petroliferous surface exposures 

of the basin's south flank can be separated into two 

distinct types with respect to geometry and 

W:D(width/:depth) ratio. "Type one" is characterized by 

a tabular geometry controlled by a planar lower 

bounding surface, an average channel depth of7.6 m, and 

an average W :D ratio of 8.9. The planar channel bottom 

results from underlying resistant carbonate units whose 

early lithification restricted downcutting and caused 

more extensive lateral channel migration compared to 

that of streams forming "type two" bodies. Type two 

bodies are characterized by a lenticular geometry, by an 

average channel depth of 5.7 m, an average W:D ratio of 

3.6, and a concave-upward lower bounding surface. The 

absence of resistant carbonate rocks underlying streams 

that deposited type two bodies resulted in stream 

channels that, although similar in size, did not migrate 

laterally as much as those of type one. The size of 

individual marginal-lacustrine channel sandstone bodies 

(and therefore reservoir units) is largely dependent upon 

induration of the substrate across which streams flowed. 

Along the south shore of the lake, erosion 

associated with numerous shoreline fluctuations and 

relatively shallow nearshore water depths precluded the 

development and preservation of thick, areally extensive, 

lacustrine clastic beach and bar deposits. However, lacustrine siliciclastic bars up to several meters thick formed 

excellent reservoirs along the northeast margin of the 

lake near Red Wash field, where the depositional dip was 

apparently steeper and shoreline fluctuations more 

restricted than those of the lake's southern margin. 

Carbonate-grainstone-packstone reservoir units, which 

32 

were generally deposited as carbonate shoals, commonly 

as thick as 1 m, yield minor oil in the northeastern area of 

the basin. 

Deeply buried overpressured strata are 

characterized by reservoirs whose matrix permeability 

values are near, and are commonly below, 0.1 md and 

whose porosity values (most porosity being secondary) 

range from 5 to 10 percent. These same strata contain 

open fractures and transmissivity (T = permeability X height) values through producing intervals that 

are commonly high. Combined primary and secondary 

porosity values of 10 to 16 percent are common in 

normally pressured oil reservoirs, and matrix 

permeability values may be as high as 1 d. Transmissivity 

values for such sequences can be relatively high because 

of their high matrix permeabilty. Gas-bearing sandstone 

reservoirs in the basin that commonly contain porosity 

values ranging from 8 to 16 percent, but whose matrix 

permeability values are 0.1 md or less, are frequently 

termed "tight gas" sandstones. Transmissivity values for 

productive "tight gas" intervals are very low because of 

few natural open fractures. 

Basin Development and Resultant 

Sedimentation Patterns During the 

Transition from Sevier- to Laramide-Style 

Tectonism, Central Utah 

Karen J. Franczyk, Timothy F. Lawton, and 

J. K. Pitman 

The final phase of Sevier-style tectonism and the 

initiation of Laramide-style tectonism in central and 

east-central Utah during latest Cretaceous time 

segmented the foreland basin and formed several intermontane basins, both on the thrust sheets and in the 

foreland basin area. An unsegmented foreland basin 

adjoined the eastern edge of the thrust front from late 

Early Cretaceous until late Campanian time. The Castlegate Sandstone and its inferred western equivalents were 

the last strata deposited prior to segmentation of the 

foreland basin. Within the study area, the Castlegate 

depositional system consisted of two major alluvial-fan 

complexes that fringed the thrust belt. The fans graded 

laterally into a sand-rich alluvial plain (Castlegate 

Sandstone) across which sediment was transported 

dominantly eastward toward the coastline. Thereafter, 

eastward-propagated thrusting along a blind thrust fault 

created, within the study area, a triangle zone near the 

thrust front that segmented the most proximal part of the 

Castlegate depositional area. Consequently, this 

foreland-basin sequence cannot be traced continuously 

from proximal alluvial-fan deposits into distal fluvial 

deposits. 
East of the thrust front, isopachs of the Castlegate 

indicate thickening westward and northward from the 

southeastern Wasatch Plateau area; the thinner area 

might have resulted from postdepositional erosion 

caused by the initial uplift of the San Rafael structure. 

West of the thrust front, small intermontane basins 

formed on top of the thrust sheets. Sediment transported 

into these basins came from both eastern and western 

sources. In these intermontane basins, facies graded 

within a few kilometers from conglomeratic alluvial-fan 

deposits near the margins to floodplain and lacustrine 

deposits in the interior parts. These beds previously have 

been correlated with formations of the foreland basin 

depositional sequence. These intermontane basins 

existed from latest Campanian through late Paleocene 

time, and during their formation probably migrated a 

short distance eastward during their formation atop the 

thrust sheets. 

East of the thrust front, latest Campanian 

deposition was associated with northward-flowing rivers 

that transported sediment from feldspar-rich source 

areas southwest of the study area. A thin unit of 

uppermost Campanian strata immediately east of the 

thrust front indicates either extensive postdepositional 

erosion or, more likely, slow subsidence combined with 

depositional onlap of the thrust front in this area. 

Further segmentation of the foreland basin 

occurred when a major uplift of the San Rafael structure 

in very late Campanian or early Maastrichtian time gave 

rise to a new intermontane basin in the area between the 

thrust front and the west flank of the San Rafael uplift. 

Northwestward-flowing, pebble-bearing braided rivers 

deposited the first sediments in this new basin. 

Subsequently, a thick Maastrichtian clastic sequence 

formed in this basin. Like the uppermost Campanian 

strata, these Maastrichtian beds were derived from 

sources to the south, but they contain significantly less 

feldspar than the youngest rocks of the foreland basin 

system in this area. 

East of the thrust front, during the Paleocene, 

deposition was intermittent and within restricted areas; 

centers of basin subsidence and locations of uplifts 

shifted rapidly. During this time, the last phase of 

Sevier-style thrusting occurred in north-central Utah, 

and Laramide-style structural elements, such as the 

Uncompahgre and Uinta uplifts, became active. By early 

Eocene time, the isolated basins both east and west of the 

thrust front had filled, and the depositional systems of the 

region were integrated into a single, large, lacustrinedominated complex where the youngest part of the 

Flagstaff Member of the Green River Formation 

accumulated. 

33 

Application of Ground-Penetrating Radar 

to Development of Reservoir Models 

Donald L. Gautier, C. J. Schenk, and 

Gary A. Olhoeft 

Studies of recent sandy sediments can be used to 

predict reservoir heterogeneities if we are able to 

investigate sand bodies in three dimensions over 

appropriate distances. Many studies of recent sediments 

have relied upon examination of relatively small samples 

in cores or trenches. Ground-penetrating radar permits 

the examination of bedforms, bedsets, and individual 

strata or sets of strata over distances of several 

centimeters to a few tens of meters, which are the same 

distances over which significant variations in reservoir 

properties are commonly observed. 

Ground-penetrating radar was used to analyze 

structures of eolian dunes at Great Sand Dunes National 

Monument, Colorado. Transceivers of five frequencies 

(900, 500, 300, 150, and 80 MHz) were used along 

perpendicular traverses, each approximately 300 m in 

length. A small area of the sand dunes was selected for 

investigation, consisting of a large ( > 30 m thick) dune 

complex with small ( < 1 m thick) superimposed dunes on 

its eastern flank. The locations of the traverses were 

carefully surveyed with laser theodolite, and appropriate 

corrections were made for topography and electrical 

conductivity of the sand. The investigative power of 

ground-penetrating radar is inversely proportional to the 

depth of investigation: higher frequences yield greater 

resolution and lower frequencies provide greater 

penetration. Resolution of features a few centimeters 

thick was possible in the upper few meters of the dune 

complex by means of the 500 or 900 MHz transceivers. 

Lower frequency radar (80 to 150 MHz) was capable of 

penetrating to depths of several tens of meters. 

The radar sections showed that the lee slope of the 

dune complex prograded eastward across fluvial sands 

and gravels. The internal structure of the dune complex 

consisted of a large set of cross strata that graded 

east-northeast into a complex of smaller, multiple sets 

and then back to a large set with multiple smaller sets 

along its present lee slope. Bounding surfaces of various 

sizes were evident within the larger dune sets. Of 

particular interest were the common low-angle, downwind bounding surfaces within the large dune complex. 

These surfaces bounded sets of low-angle strata probably 

of wind-ripple origin. The cut-and-fill structures 

observed along the eastern flank of the dune complex 

probably reflect "vortex scour" and fill resulting from 

east winds blowing opposite the principal wind direction 
for sand transport. The location of the water table was 

visible as subparallel reflections beneath the dune 

complex. 

Our results indicate the potential of ground-based 

radar for the detailed interpretation of structures in 

recent sediments over distances ordinarily out of reach of 

the sedimentologist or reservoir engineer. Radar studies 

have potential for revealing complex structures within 

otherwise relatively homogeneous sand bodies-complex 

structures that can be expected to affect reservoir quality 

in ancient sediments. 

A Seismic Reflection Study of Miocene 

Listric Faulting North of 

Lake Mead, Nevada 

J.A. Grow, R.G. Bohannon, J.J. Miller, and 

R.E. Anderson 

Six industry seismic reflection profiles in the Virgin 

River valley north of Lake Mead, Nevada, are tied to the 

Mobil Virgin River No. 1A exploration well (TD = 5,964 

m, deepest well in Nevada; top of Precambrian crystalline 

rocks at 5,837 m; top of Paleozoic at 3,355 m; top of 

Mesozoic at 2,044 m; Miocene and younger above 2,044 

m). This part of Virgin River valley is in the Basin and 

Range province near the western edge of the Colorado 

Plateau and lies between the Mormon and North Virgin 

Mountains. The well data and seismic lines show no 

evidence of the Mesozoic thrust faults or associated 

compressional structures described in the Mormon 

Mountains and Tule Springs Hills to the north. Because 

this area probably did not inherit a strong Paleozoic or 

Mesozoic structural fabric, it provides an excellent 

opportunity to study the structures formed during the 

late Cenozoic extensional deformation. 

East-west lines show three subbasins beneath the 

Neogene valley fill. The subbasins are separated by two 

large east-tilted fault blocks with north-trending axes. In 

the western subbasin, well-imaged Miocene synextensional basin-fill sediments fan downward against a 

west-dipping listric fault that decreases in dip from 40° at 

0.8 seconds depth (two-way travel time) to 0° at 3.0 

seconds. North-south lines show gentle folding 

contemporaneous with the Miocene extensional 

deformation, confirming earlier geologic studies 

suggesting that north-south shortening occurred 

simultaneously with east-:west extension, and that the 

overall direction of motion for the extensional blocks in 

this part of the Basin and Range province was to the 

southwest. 

Both the sedimentary strata and listric fault are 

expressed by strong reflections (where the fault separates 

34 

basement and cover), but the listric fault shows only weak 

intermittent reflectors where it penetrates the basement, 

at depths between 2.4 and 3.0 seconds (increasing to the 

southwest). Other weak intermittent, subhorizontal 

reflections can be seen to depths of 7 seconds on 

Vibroseis® lines which have been reprocessed using the 

extended correlation technique. We see no evidence in 

these reflection data for or against a postulated major 

regional detachment fault beneath the Virgin valley. If 

such a fault exists, it juxtaposes rocks of such low 

impedance contrast that lateral coherence of reflections 

is precluded. 

Effects of Basin Evolution on 

Source-Rock Characteristics of the 

Woodford Shale, Anadarko Basin, 

Oklahoma 

Timothy C. Hester, James W. Schmoker, and 

Howard L. Sahl 

The Woodford Shale (Late Devonian-Early 

Mississippian) is an organic-rich, highly compacted, 

"black" shale that is a significant hydrocarbon source 

rock in the Anadarko basin of Oklahoma. The Woodford 

is divided here, on the basis of log character, into three 

informal stratigraphic units-the upper, middle, and 

lower members of the Woodford Shale. Higher kerogen 

content of the middle member is the physical basis for 

this subdivision. 

Depositional patterns of the three Woodford 

members within the study area reveal a positive 

structural feature parallel to and about 120 km north of 

the Wichita Mountains front (along the trend of cross 

section E-E', fig. 1) that divided the Woodford into 

northeast and southwest depocenters. This positive 

structural feature was a hinge line separating areas of 

regional basement flexure during Woodford deposition. 

From the hinge line, each member thickens to the 

southwest (cross sections A-A', B-B ', C-C', G-G ') in 

response to subsidence along the axis of the southern 

Oklahoma aulacogen. To the northeast, thickness of the 

lower and middle Woodford members remains nearly 

constant, reflecting a stable shelf environment, whereas 

the upper member thickens significantly (cross sections 

A -A ', B -B ', C -C ', D-D ') reflecting and dating initial 

development of the Sedgwick basin of south-central 

Kansas. 

The Woodford Shale was deposited during the 

transition between two major stages of structural 

development that together formed the present -day Anadarko basin-the first-stage southern Oklahoma aulacogen (early Paleozoic) and the second-stage foreland-style 
I= 

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50 50 

B<sw> B'<NE) 0 ~:_--------~~=---------------------~0 

50 

100 100 

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I UPPER 

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50 50 

100 100 

150 

200 

250 9Q] 300 c 

D<NW> D~sE> 

.:J ~~~:, 100 100 

E(NW) E'<sE> 

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100 100 

150 

0 10 20 30 Ml 

0 10 2'0 --~4'o KM 200 

250 

Figure 1 (Hester). Smoothed regional cross sections of the three informal members of the Woodford Shale (Late Devonian-Early Mississippian) depicting the 

influence of Anadarko basin evolution on the distribution of Woodford Shale sediments. Index maps show study area, lines of cross section, and State and county 

boundaries. 
downwarping (late Paleozoic). Varying burial depths of 

the Woodford during the second stage of Anadarko basin 

development overprinted thermal maturity patterns onto 

Woodford depositional patterns. As a result, Woodford 

sediments in the northeast portion of the study area 

(cross section D-D '), which are dominated by the upper 

member (TOC (total organic carbon) averages 2.7 wt. 

percent), remain immature to marginally mature with 

respect to oil generation. More deeply buried Woodford 

sediments in the southwest portion of the study area 

(cross section G-G '),which are dominated by the middle 

and lower members (TOC averages 5.5 and 3.2 wt. 

percent, respectively), are mature to postmature with 

respect to oil generation. Thus, most hydrocarbons 

sourced by the Woodford Shale of the study area were 

generated from the lower and middle members, which 

contain about three-fourths of the thermally mature 

organic carbon. 

Architecture of Clastic Facies and 

Location of Coals Associated with a 

Major Marine Transgression-The 

Mid-Cretaceous of the Kaiparowits 

Plateau, Utah 

Robert D. Hettinger and Peter J. McCabe 

The upper part of the Smoky Hollow Member and 

lower 100 m of the John Henry Member of the Straight 

Cliffs Formation are well exposed along depositional 

strike and dip in the region west of the town of Escalante 

in the northern part of the Kaiparowits Plateau, southern 

Utah. A series of sections tied into photo mosaics help 

explain the complex facies architecture of this interval. 

The strata are divided into two parasequence sets of 

intertonguing tidal channel, shoreface, and offshore 

marine deposits. The lower set appears to backstep 

toward the southwest, whereas the upper set clearly 

forward steps toward the northeast. These deposits are 

correlated over 19 km to the northwestern part of the 

plateau, where the strata contain significant coal 

deposits. 

The lower parasequence set is underlain by about 

30m of trough crossbedded pebbly sandstones that are 

laterally amalgamated. This distinct and laterally 

extensive pebbly unit, informally called the Calico bed, is 

thought to have been deposited by braided rivers. The 

Calico grades upward into interbedded sandstones and 

mudstones which form the base of the lower parasequence set. The sandstones have erosional bases and 

contain basal lags of mud clasts and logs with Teredolites. 

Bidirectional trough and planar tabular crossbeds and 

ripple laminae suggest accumulation under tidal 

36 

influence. These sediments are truncated by an erosion 

surface which gently dips toward the northeast. It is 

covered by a thin conglomerate of extraformational 

pebbles and cobbles, interpreted to be a lag deposit on a 

ravinement surface. The conglomerate lag is overlain by 

about 2 m of swaley cross-stratified sandstone which is 

capped by a shark-tooth lag that marks the condensed 

interval between the two parasequence sets. 

The upper parasequence set, which forms the 

lower part of the John Henry Member, contains about 10 

parasequences that are arranged in a forward-stepping 

stack. A typical parasequence consists of interbedded 

mudstones and hummocky cross-stratified sandstones 

that pass upward into pebbly sandstones with swaley 

cross-stratification. In the western end of Upper Valley, 

only 2 m of strata separates the shark-tooth lag from the 

lowest swaley cross-stratified sandstone. In less than 8 

km eastwards, this 2-m interval thickens to about 55 m 

because of the forward-stepping geometry. Tidal channel 

deposits intertongue with and replace shoreface 

sediments in a landward direction. These channels are 

infilled with pebbly sandstones containing abundant 

broken oyster and Inoceramus shells. 

Major deepening events have tentatively been 

correlated into the strata of the northwestern part of the 

plateau. In this region tidal channel sandstones interfinger with terrestrial mudstones and coals. The coals, 

which are up to 4 m thick, accumulated lateral to the 

forward-stepping shoreface deposits of the Escalante 

area and appear to have formed in mires several 

kilometers landward of the shoreline. 

Reservoir Characteristics of the Lower 

Cretaceous J Sandstone in the Kachina 

Field, Denver Basin, Colorado 

Debra K. Higley 

Thin-section petrography, well logs, and core 

porosity-permeability studies show that porosity loss in 

the Lower Cretaceous J sandstone in the Kachina field 

was primarily the result of early precipitation of quartz 

cement. Porosity and permeability were further reduced 

by authigenic kaolinite and other pore-filling clays. 

Reservoir facies are primarily fine- to medium-grained 

quartzarenite and sublitharenite. Producing facies are 

thin-bedded, trough- and planar-crossbedded 

distributary channel sandstone. More than 1.3 million 

barrels of oil have been produced from the Kachina field. 

Overlying mudstone is the seal for structurally/stratigraphically trapped hydrocarbons. 

J sandstone core from 4,269 to 4,328 ft depth in the 

B-1 Sheetz (SWY..SWY.. sec. 14, T. 3 S., R. 52 W.), Sheetz 
no. 6 (SWY4SWY4 sec. 23, T. 3 S., R. 52 W.), and 

Raymond Thomas no. 1 (NEY4NEY4 sec. 23, T. 3 S., R. 52 

W.) drill holes was sampled and analyzed petrographically. Core median permeability is 87, 72, and 281 

millidarcies, and core median porosity is 21, 23, and 24 

percent, respectively, for the three drill holes. Intergranular porosity in the thin sections studied ranges from 14 

to 22 volume percent; minus-cement porosity ranges 

from 26 to 43 percent. Porosity is mainly primary and 

secondary intergranular in origin; minor amounts of 

intragranular and microporosity may be present. Volumetrically, the most important authigenic mineral is 

syntaxial quartz cement, which ranges in amount from 

about 4 to 21 percent. Kaolinite plus other clays vary 

from 4 to 14 volume percent. These clays are generally 

incorporated with fine-grained detrital material and 

occur within pores and pore throats. 

Paragenesis of reservoir facies comprises the 

following sequence of events: (1) minor sediment 

compaction prior to (2) formation of quartz and feldspar 

overgrowths, (3) calcite cementation and replacement of 

lithic grains, ( 4) dissolution of calcite, which results in 

restoration of primary porosity and creation of secondary 

porosity, (5) collapse of detrital material into resulting 

pore spaces and growth of illite-smectite, chlorite, and 

other pore-filling clays, and (6) formation of authigenic 

pore-filling kaolinite. 

Computer Display of Petroleum 

Exploration Through Time in the Denver 

Basin of Colorado, Nebraska, and 

Wyoming 

Debra K. Higley and Kenneth I. Takahashi 

Denver basin petroleum exploration through time 

is animated and displayed on a Macintosh computer. 

Trends in basin-wide and individual county exploration 

are shown with drill-hole data for 5-year increments from 

1900 through 1983. 

The source of drill-hole data is the Petroleum 

Information Corp. Well History Control System 

database. Drill-hole location, completion date, and 

production data were analyzed using a series of U.S. 

Geological Survey computer programs which divided the 

Denver basin into approximately Y4 mi2 grid cells and 

calculated the type and highest level of petroleum 

production within each cell. Mapped data show the 

earliest time interval of exploration and the oil and gas, 

oil, gas, or nonproducing category of each grid cell. A 

grid cell with an oil and gas symbol, for example, might 

contain an oil and gas, a gas, and a nonproducing drill 

hole, whereas a dry-hole cell has only one or more 

nonproducing drill holes within it. 

37 

The exploration maps were generated with 

Dynamic Graphics Interactive Surface Modeling 

software on a VAX 111780 minicomputer. The maps 

were then scanned and processed with Super Paint 

software on a Macintosh Plus computer. Denver basin 

political boundaries were created with Macintosh Mapmaker software. Hypercard software is used to select and 

present basin, county, and field map images. 

In this animated display, petroleum exploration 

begins with scattered shallow drilling concentrated 

around basin margins, and with development in the late 

1800's and early 1900's of the Florence oil field (which 

produces from the Cretaceous Pierre Shale). Exploration 

proceeds to a Cretaceous J and D sandstones surge in 

drilling in the 1950's, and continues with discovery in 

1970-83 of Wattenberg gas field and other Cretaceous 

Dakota Group fields, and Paleozoic fields in the 

southeast part of the basin. 

Carbon Isotopic Trends in Peats and 

Coals-Clues to Carbon History and the 

Environment of Coal-Forming Mires 

Charles W. Holmes 

The global biogeochemistry of carbon is extremely 

complex. Carbon dioxide released into the atmosphere as 

a result of the combustion of fossil fuel is added to that 

naturally respired by the biosphere and released from the 

hydrosphere. The carbon cycle has been and continues to 

be a subject of much concern as it is C02 that is held 

responsible for much of the so-called "greenhouse" 

effect. Recent modeling studies have revealed significant 

gaps in information that limit our ability to define the 

paths and interactions of the gases within the biosphere 

and oceans. The measurement of carbon and carbon 

isotopes in coal and in modern peat-forming 

environments has been undertaken as a means of better 

defining the balances within the carbon cycle and 

determining the usefulness of o 13C trends as clues to the 

environmental development of coal-forming mires. 

The o 13C of plants, the original materials that form 

coal, is a function of plant physiology and the isotopic 

composition of the atmosphere in which plants grow. The 

physiological effect is created by the photosynthetic path 

( C3 plants are significantly depleted in 13 C with respect to 

C4 plants) and (or) habitat (mesic plants are depleted in 13C with respect to hydric plants). In the Okefenokee 

Swamp, Georgia, for example, the hydric C3 water lily 

(Nymphaea ororata) has a o

13C of -22.5%o , whereas the 

C3 mesic fern (Woodwardia virginica) has a o

13C of 

-30.0%o. Measurements on the same plants, subjected to 

atmospheric C02 with varying o13C, have demonstrated 
that carbon fixed in plants does reflect these systematic 

variances between hydric and mesic plants. 

Peats forming in environments that are 

progressively inundated as a result of a relative rise in 

base level would be expected to show a succession of 

plants from mesic to hydric. The carbon signature of 

these peats is initially negative (relatively light) but 

becomes heavier as the peats are formed from plants with 

an increasing hydric component. The o

13C trends in the 

Anderson, Smith, and Lake De Smet coals of the Powder 

River basin are of this lighter-to-heavier type. This 

information, coupled with the palynological data from 

these beds, suggests that the plant physiological 

environment resulting in the formation of these coals was 

similar to the modern environment within the Okefenokee Swamp of southern Georgia. 

In raised mires, the isotopic composition of the 

atmosphere is the dominant factor in influencing the 

isotopic variability of the plants. Measurements have 

shown that, due to recycling, the C02 in the local air is 

depleted in 13C with respect to atmospheric averages. 

Continued recycling and deposition of plant material on 

the forest floor would lead to progressive lighter carbon 

being available to the plants, which would be reflected in 

the more negative o

13C in the resultant peat. This process 

accounts for the trend observed in the modern peats and 

Tertiary coals of Borneo. 

The data therefore suggest that the trends of o13 C 

in peats and the resultant coal are a measure of the 

environment of formation, and the o13C of coals may also 

provide data on the variation in isotopic composition of 

atmospheric carbon through geologic time. 

The Search for Subtle Traps Across 

Onshore Alaska 

David G. Howell 

For most of this century the U.S. Geological Survey 

has collaborated with industry and academic scientists 

exploring and characterizing the petroleum potential of 

Alaska. Discoveries in Cook Inlet, Point Barrow, and 

Prudhoe Bay are the obvious successes. These three oil 

and gas fields lie along north and south margins of 

continental Alaska; between these two areas Alaska is 

viewed as a collage of tectonostratigraphic terranes that 

have agglomerated since approximately Middle Jurassic 

time. The stratigraphy of these terranes indicates a 

tectonic mixing of oceanic magmatic arcs and continental 

slivers. The latter presumably represent truncated 

portions of the North American margin. Mapping and 

geophysical experiments indicate that these terranes are 

either enveloped or underlain by a vast volume of gray38 

wacke. Although these rocks initially posed as an 

intriguing potential hydrocarbon source, numerous 

Rock-Eval and associated thermal studies now suggest 

that the sedimentary strata are over-mature, rendering a 

deep-gas scenario only improbable. 

The greater part of the accretion tectonism of 

interior Alaska had ended by the close of the Mesozoic. 

Latest Cretaceous to . Neogene sedimentary overlap 

sequences reflect three general phases of basin 

accumulation, all of which are nonmarine. Locally these 

basin strata are as thick as 5 km, but nowhere is there 

thought to be anything other than small quantities of 

dry-gas resources. 

In spite of this pessimistic forecast, two areas 

remain of interest owing to recent preliminary studies 

that suggest the potential for oil accumulations. The first 

is the Yukon Flats-Kandik basin area of east-central 

Alaska. Here, thermally over-mature Mesozoic strata lie 

structurally(?) above a thick Precambrian to lower Mesozoic sequence that remains thermally within the oil 

window; furthermore, several horizons within this lower 

sequence are excellent potential hydrocarbon source 

rocks. Understanding the tectonic history, the regional 

structural patterns, and the subsurface extent of 

thermally cool strata will better enable us to evaluate this 

region. 

The second area is the region along the northern 

margin of the Brooks Range. Here, tectonic duplexing 

likely thickened and shortened sequences of organically 

rich lower and middle Mesozoic strata along with early 

foreland basin deposits (Upper Jurassic and Lower 

Cretaceous). These same beds are the source of the oil 

trapped in the giant Prudhoe Bay field, and migration of 

the oil probably followed pathways up the south flank of 

the northerly migrating lithospheric bulge, which formed 

as a consequence of tectonic loading in the interior zone 

of the Brooks Range thrust belt. Because this bulge once 

existed farther south, tracking its movement history may 

predict other occurrence of trapped oil. 

Rifts and Hot Spots-A Model for the 

Proterozoic Midcontinent Rift System of 

North America 

D.R. Hutchinson and R.S. White 

Hot spots beneath young, rifted continental 

margins have been identified by their association with 

massive short -lived eruptions of basalts that contain 

distinctive geologic, geophysical, and geochemical 

signatures. This volcanism can be explained by 

decompression melting and rapid extrusion of igneous 
material during lithospheric extension above a broad, 

asthenospheric, thermal anomaly-a hot spot. Perhaps 

the best studied modern hot-spot/rift system is in the 

North Atlantic, where the continental margins of 

Norway, Greenland, and Rockall formed in association 

with the Iceland hot spot. 

The Middle Proterozoic (1.1 Ga) Midcontinent 

Rift System (MRS) of North America shares many 

characteristics with modern rifted continental margins 

and flood basalt provinces. The volume of synrift extrusive basalts in the MRS (1.3X 106 km3

) rivals that of some 

of the Earth's largest and much younger flood basalt 

provinces, such as the Deccan traps. The areal limit of 

MRS basalts can be roughly contained within a circle 

1,600 km in diameter, well within the size range of 

oceanic hot-spot swells. Basalts in the MRS were 

extruded over a period as short as 10 to 13 m.y ., with the 

bulk of the eruption possibly concentrated in as little as 2 

to 3 m.y ., a time frame consistent with the rapid extrusion 

estimated in younger flood basalt provinces such as the 

Columbia River, Parana, Deccan, or North Atlantic 

Tertiary provinces. Stratigraphic and structural studies 

indicate that much of the MRS volcanism occurred at or 

above sea level, which is predicted by the dynamic and 

isostatic uplift associated with a mantle thermal anomaly. 

Geochemical signatures of the basalts, such as the 

presence of basal picrites, are consistent with higher melt 

percentages associated with higher mantle temperatures. 

Deep seismic-reflection profiles collected as part of 

the Great Lakes International Multidisciplinary Program 

on Crustal Evolution (GLIMPCE) can be used to 

constrain end-member models of melt thickness and 

stretching factors, and therefore yield an estimate of the 

potential temperature of the mantle at the time of rifting. 

(The potential temperature is the temperature that the 

mantle would have if brought to the surface adiabatically 

without melting.) We determine that the mantle potential 

temperature was about 1,500 to 1,570 °C during rifting, 

which is about 350 °C hotter than the modern mantle 

potential temperature (1,280 °C) but may have only been 

100 to 200 °C hotter than 1.1-Ga mantle. A thermal 

anomaly of 100-200 °C is consistent with that estimated 

for modern hot-spot swells, such as the Cape Verdes or 

Hawaii, and for modern hot -spot/rift systems, such as the 

North Atlantic province. We call this thermal anomaly in 

the MRS the Keweenaw hot spot. 

Gravity modeling requires that much of the lower 

crust beneath the basalts of the MRS is more dense than 

the adjacent rift flanks or unrifted crust; this density 

anomaly is interpreted as evidence for massive igneous 

(probably gabbroic) underplating. The thickness of the 

upper Keweenawan postrift clastic deposits can be used 

in conjunction with the gravity model to examine 

subsidence and stretching factors. Our combined analysis 

yields stretching factors of 3 to 4 within the MRS, and 

39 

suggests that the thermal anomaly associated with the 

Keweenaw hot spot either dissipated or migrated away 

during the accumulation of the postrift units. Why this 

huge continental rift ceased extending when it was so 

close to complete break-up is unknown, but tectonic 

forces operating in the nearby coeval Grenville orogen 

probably played a critical role. 

Petroleum Geology Studies in the Santa 

Maria Province, California 

Caroline M. Isaacs, J. David King, Richard M. 

Pollastro, and Colin F. Williams 

The Santa Maria Province Project is a basin 

evolution study undertaken in the coastal California 

margin by the U.S. Geological Survey's Evolution of 

Sedimentary Basins Program and the Onshore Oil and 

Gas Investigations Program. The basins included within 

the Santa Maria province are the onshore Santa Maria, 

offshore Santa Maria, Huasna-Pismo, Santa BarbaraVentura, Sur, and Santa Lucia basins (fig. 1). The 

province has significant petroleum reservoirs and is 

especially important as the major location of fractured 

siliceous reservoirs within the Miocene Monterey 

Formation (fig. 2). The province is ideally located for 

study of the hydrocarbon-source characteristics of the 

prolific Monterey Formation, as this formation is the only 

petroleum source rock in the onshore and offshore Santa 

Maria basins, as well as a principal source rock 

throughout the province. Studies of the fractured 

reservoirs and hydrocarbon-source rocks within the 

Santa Maria province are also important to ongoing 

assessment of undiscovered hydrocarbon reserves in the 

little-explored basins offshore central and northern 

California, where the Monterey Formation is regarded 

Figure 1 (Isaacs). Neogene marine basins in Santa Maria 

province area. 
5,000'-

10,000'-

15,000'-

QTu- Quaternary-Tertiary, undiff. 

Tf- Foxen Formation 

Ts- Sisquoc Formation 

Tm- Monterey Formation 

Tps- Point Sal Formation 

Ti- Lospe Formation 

- 5,000' 

-10,000' 

0 1 2 4 MILES 

1-l --r""j .1....1 ,....., -,.-L• -,...---'---'' -15,000' 

0 1 2 3 4 KILO~TERS 

Figure 2 (Isaacs). South-to-north cross section on line A-8 of figure 1. Knoxville-Franciscan, Knoxville Formation and 

Franciscan Complex. 

both as a major potential petroleum source and as an 

important potential petroleum reservoir. 

Despite its importance to petroleum geology in 

California, the Santa Maria province has been little 

studied in the public domain as a petroleum province, 

and many questions remain about its thermal evolution, 

its petroleum reservoir-rocks, and the source, 

maturation, and migration of its hydrocarbons. For 

example, the viscosity and density of the oils within the 

province are highly variable; is the variation due to 

characteristics of source, maturation, or migration? Do 

various facies of the Monterey Formation mature 

differently? Are particular facies or lithotypes better 

petroleum source rocks, and why? What organic maturity 

parameters are useful, and how are they related to other 

measures of diagenesis and thermal exposure? Reported 

present-day thermal gradients vary considerably over the 

region (range, 24-67 °C/km); does this variation reflect 

variations in heat flow or in thermal conductivity of the 

sedimentary cover? How has the thermal history of the 

province been affected by tectonism? 

To examine these questions, the USGS Santa 

Maria Province Project has initiated a wide-ranging study 

of diagenesis, thermal history, and organic geochemistry 

of the province. Specific regional efforts underway 

include: (1) a coordinated study of thermal history 

involving clay diagenesis, silica diagenesis, biomarker 

maturation characteristics, and fission-track thermal 

analysis of subsurface sections throughout the province; 

(2) a major survey of present-day thermal gradients and 

heat-flow distribution; and (3) an international 

cooperative effort with colleagues from industry and 

academia focused on the organic geochemical 

characteristics of Monterey kerogens and oils from the 

province. In addition, topical efforts underway include: 

(1) isotopic study of fluid inclusions in fractured 

reservoir rocks; and (2) characterization by scanning 

electron microscopy of lithotypes within the fractured 

reservoirs. 

40 

Geologic Evolution of the Uinta-Piceance 

Basin Province, Northwestern 

Colorado and Northeastern Utah 

S.Y. Johnson, M.L. Tuttle, Bruce Bryant, R.F. 

Dubiel, T.D. Fouch, K.J. Franczyk, V.J.S. 

Grauch, M.A. Grout, R.C. Johnson, C.M. 

Molenaar, D.J. Nichols, K.M. Nichols, V.F. 

Nuccio, Fred Peterson, J.K. Pitman, 

W.J. Perry, Jr., D. Sawatzky, R.W. Scott, 

E.R. Verbeek, and R.B. Wanty 

The Uinta-Piceance Basin province (UPBP) of 

northwestern Colorado and northeastern Utah has 

undergone a complex Phanerozoic history characterized 

by at least five distinct phases (Cambrian through 

Mississippian, Pennsylvanian-Permian, Triassic-] urassic, 

Cretaceous, Paleogene) of regional tectonism, basin 

development, and sedimentation. Basinal strata were 

deposited on a Precambrian basement of crystalline and 

metasedimentary rocks cut by Proterozoic faults of 

variable orientation. The UPBP formed part of the 

continental platform-shelf on the northwestern flank of 

North America during the early and middle Paleozoic. 

Cambrian through Mississippian strata consist 

mainly of shallow-marine limestone, dolomite, shale, and 

quartzite; contain major unconformities; and thicken 

westward. Pennsylvanian-Permian block uplifts 

associated with the transpressional(?) ancestral Rocky 

Mountain orogeny segmented this early to middle Paleozoic platform-shelf into the Eagle, Paradox, and Oquirrh 

basins. Both basin-margin tectonics and cyclic 

eustatic/climatic fluctuations strongly controlled 

deposition of the nonmarine/marine, mixed clastic, 

carbonate, and evaporitic fill of these basins. 

During the early Mesozoic, the UPBP formed part 

of a slowly subsiding continental platform. TriassicJurassic rocks include considerable eolian, alluvial, and 
lacustrine deposits that become significantly thicker and 

grade into more marine facies from east to west. Paleozoic and early Mesozoic strata in the westernmost part of 

the UPBP were uplifted and thrust eastward during the 

late Mesozoic Sevier orogeny, which resulted in 

subsidence in the bordering foreland basin. The 

sedimentary history of the UPBP portion of this foreland 

basin is recorded by thick nonmarine deposits within and 

adjacent to the thrust belt that grade eastward into 

thinner accumulations of marginal-marine and marine 

rocks. The geometry and style of regional compressional 

deformation changed dramatically in the latest 

Cretaceous with onset of the Laramide orogeny. Laramide uplifts segmented the UPBP Cretaceous foreland 

basin into the Uinta and Piceance intermontane lacustrine basins. The geometry of these lacustrine basins is 

notably different from that of the Pennsylvanian-Permian 

segmented UPBP basins. 

Major scientific problems addressed in the UBPB 

study include the following: (1) documenting and (or) 

refining basin stratigraphy and chronostratigraphy; (2) 

clarifying relations between sedimentation and the 

diverse Phanerozoic tectonic styles; (3) describing and 

modeling the geochemical and diagenetic evolution of 

basin constituents; and ( 4) relating the tectonicsedimentary and geochemical-diagenetic histories to 

development of energy and mineral resources. The 

UPBP has important hydrocarbon resources, including 

oil, gas and tar sands. Paleogene lacustrine rocks host 90 

percent of the Nation's oil shales. The UPBP also 

contains significant coal, evaporite, phosphate, uranium, 

and metal deposits. 

Publications that are planned for the UPBP study 

include the following: (1) gravity and magnetics maps; 

(2) a remote-sensing-lineament map; (3) basement 

structure contour and Phanerozoic sedimentary rock 

thickness maps; ( 4) a series of regional stratigraphic and 

chronostratigraphic cross sections of Phanerozoic rocks; 

(5) balanced structural cross sections across the Sevier 

orogenic belt; ( 6) detailed stratigraphic-sedimentologic 

charts of selected units; (7) surface vitrinite reflectance 

map; (8) paleogeographic maps; (9) a volume of papers 

describing and (or) modeling and synthesizing aspects of 

the geophysics, structural geology and tectonics, physical 

stratigraphy, biostratigraphy, sedimentology, paleogeography, paleoclimatology, petrology and diagenesis, 

geochemistry, heat flow and thermal maturity, and paleohydrology of the UPBP; and (10) a volume of papers on 

the geochemistry of Green River Formation oil shales. 

41 

Diagenesis of Sandstones in the Norphlet 

Formation (Upper Jurassic), Escambia 

County, Alabama 

C.W. Keighin and C.J. Schenk 

The Upper Jurassic Norphlet Formation is an 

important hydrocarbon reservoir in Baldwin and Mobile 

Counties, and offshore in Mobile Bay, Alabama. It 

produces gas condensate in the Flomaton field in Escambia County, and underlies the oil-bearing Smackover 

Formation in the Little Escambia Creek field (southeast 

of Flomaton field), at a depth of approximately 15,500 ft 

(4,725 m). Sandstones of the Norphlet examined in cores 

from two drill holes in the Little Escambia Creek field 

are largely fluvial in origin, are moderately well to well 

sorted, very fine to coarse grained, and feldspathic, and 

are extensively altered by a complex sequence of diagenetic reactions. 

Evidence of chemical and mechanical compaction 

of these Norphlet sandstone units is slight, although 

small stylolites containing asphaltic oil are present in the 

Smackover Formation. The limited degree of compaction 

suggests that extensive early cementation by anhydrite 

and (or) calcite reduced compaction, and subsequently 

these cements were removed by migrating fluids (a 

theory shared by a 1989 study by B.E. Lock and S.W. 

Broussard). In a 1989 study, S.A. Dixon and others also 

suggested that high pore pressure, in conjunction with a 

lack of early calcite or anhydrite cement, may have 

reduced effects of compression due to deep burial. X-ray 

diffraction indicates the presence of halite, but none was 

preserved in thin section. Migrating fluids, in addition to 

removing cements, contributed to albitization of detrital 

feldspars, subsequent leaching of feldspars and rock 

fragments, and precipitation of chlorite cement. Chlorite, 

when present, occurs as well-crystallized grain coatings 

on most framework grains. Chlorite content is quite 

variable, however, not only within the samples examined, 

but also laterally; R.L. Kugler, and S.A. Dixon and 

others, both in 1989 studies, have noted that it ranges 

from zero to several volume percent. 

Porosity is typically well developed. Intergranular 

pores are due primarily to partial-to-complete 

dissolution of cements and mineral grains, especially 

feldspar. Intragranular pores are largely the result of 

partial leaching of rock fragments, as well as due to 
microporosity formed by precipitation of clay minerals in 

earlier dissolution pores. Our evidence indicates that 

most of the porosity present in the samples examined 

from the Little Escambia Creek field is secondary and 

due to leaching of cements and framework grains. S.A. 

Dixon and others' 1989 study reached an alternative 

conclusion, that primary porosity is most significant in 

the Norphlet Formation in Lower Mobile Bay. 

Alluvial Sandstone Geometries and their 

Relationship to Coal Deposition in a 

Transgressive Systems Tract, Dakota 

Formation, Utah 

Mark A. Kirschbaum and Peter J. McCabe 

The terrestrial strata of the Dakota Formation 

were deposited during a eustatic rise in sea level. They 

are overlain by marine shales of Cenomanian age. Clastic 

strata in two areas (the western margin of the Kaiparowits Plateau in southern Utah and the southwest part of 

the San Rafael Swell in central Utah) present slightly 

different architectural relationships to associated coal 

deposits. In both areas, alluvial sandstones overlie a 

major unconformity. In the Kaiparowits region the basal 

Dakota fills paleovalleys incised into gently dipping 

Jurassic strata. In the San Rafael Swell the Dakota 

overlies the mid-Cretaceous Cedar Mountain Formation. 

In the Kaiparowits region, the alluvial sequence in 

the Dakota is from 5 to 300 m thick. Differential 

subsidence in the foreland basin resulted in an increased 

thickness of section towards the western thrust belt. Four 

widespread coal zones separate clastic units that are up 

to 20 m thick. The coal zones contain carbonaceous 

mudrock, rooted and fossiliferous mudrock, thin rippled 

sandstone and coal. Coal beds are as thick as 1.5 m in the 

study area but reach 5.5 m farther to the west. Sediments 

of these zones are thought to have accumulated in mires 

containing minor lakes and low-energy fluvial channels. 

Intervening clastic units are composed of laminated 

mudrock, rippled sandstone, and ribbonlike bodies of 

crossbedded sandstone. Rippled sandstone and mudrock 

are interpreted as crevasse splay and overbank deposits. 

Ribbon sandstones are 5-10 m thick and 50-150m wide 

and have pronounced basal scours and lateral accretion 

surfaces. They are interpreted as deposits of slightly 

sinuous streams. Within the clastic units, numerous 

coeval channels, of various sizes, suggest an anastomosed 

system of channels which may have resulted from avulsion of major river systems into the mire environment. 

In the San Rafael Swell, the Dakota Formation is 

between 0 and 40 m thick. The alluvial sequence contains 

a lower unit of interconnected crossbedded sandstones 

42 

that is traceable along depositional dip for about 80 km. 

These amalgamated channels are interpreted as valleyfill deposits. Few overbank deposits are preserved 

because channels were restricted to valleys and 

continually reworked finer sediment. Amalgamated 

channels are overlain by 2-3 m thick rippled sandstones, 

mudrock and a few discontinuous coal beds less than 1 m 

thick. The rippled sandstones are present as ribbon 

bodies which are highly sinuous. These facies are 

interpreted as the deposits of small meandering rivers 

and associated mires on a low-gradient coastal plain. 

They grade upward into crossbedded, burrowed and 

oyster-bearing sandstones and shales indicating an 

evolution into tidal and lagoonal environments. 

The difference between the two regions in the 

relation of sandstone geometry to amount of coal may be 

related to relative rates of base level rise. The sediments 

of both areas are thought to have accumulated during the 

same eustatic rise in sea level but subsidence rates were 

different. In the San Rafael Swell, the highly 

interconnected channels of the lower unit of sandstones 

preclude any coal preservation, whereas the lenticular 

coals and enclosed channels of the upper unit reflect a 

gradual rise in base level. In the Kaiparowits Plateau, the 

greater thickness of the sequence and the significantly 

greater amount of coal are thought to be due to the 

increased rate of base level rise resulting from 

subsidence in this area; also there may have been a 

tectonic control on river avulsion into the area. 

Gulf of Mexico Basin 

Evolution-Geophysical and Tectonic 

Framework 

Kim D. Klitgord, D. R. Hutchinson, and 

Hans Schouten 

Sedimentary basins seaward of the Gulf Rim fault 

zone in the Gulf of Mexico region (fig. 1A) form the Gulf 

basin, which developed along extensional and rift -shear 

zones that linked the Atlantic rift and spreading-center 

systems with plate boundaries in the Pacific during the 

early Mesozoic (fig. 2). Crustal zones in the Gulf basin 

are delimited by seismic structure, magnetic-anomaly 

character, sediment-distribution patterns, and density 

structures derived from gravity modeling within the 

framework of the plate-tectonic model in a 1986 report 

by Klitgord and Schouten and a 1988 report by Klitgord, 

Hutchinson, and Schouten. We can identify continental, 

rifted-continental, rift-stage (thick-continental), 

marginal-oceanic (thin-continental), and oceanic crustal 

zones (fig. 1B) that are modified from the crustal zones 

of a 1985 study by R.T. Buffler and D.S. Sawyer. This 
GU1LJF OJF MJEXJUCO RJEGKON TJECTONKC JFJEA'fURJE§ 

0 Paleozoic Crustal 

Fragments 

[]Late Triassic -Early 

Jurassic Rift Basins 

0 Middle To Late Jurassic Salt 

Basins And Marginal Basins 

[]Oceanic Crust 

-salt Front 

0 Post Jurassic Volcanic Zones 

= Lower Cretaceous Carbonate 

Bank Front 

Figure 1 (above and following page) (Kiitgord). Gulf of Mexico region. A, Tectonic features. 

crustal-zone distribution and paleogeographic 

reconstructions for the region are used to assess the 

paleoenvironment and shifts in centers of basin evolution 

during the Mesozoic. 

The northern Gulf basin (fig. 1A ), including the 

onshore salt basins of Texas, Louisiana, and Mississippi 

and the offshore basins beneath the West Florida Shelf, 

evolved during the Late Triassic and Early Jurassic 

within a rift-shear zone bounded by the Bahamas and 

Cuban fracture zones. The shear-zone boundary then 

shifted southward between the Cuban and Campeche 

fracture zones, where it remained during the Middle to 

43 

Late Jurassic (fig. 2). Geophysical data from the Gulf 

basin are consistent with a simple plate-tectonic model in 

which the Yucatan microplate remains attached to the 

South American plate until the end of the Jurassic. As 

the Gulf basin evolved between the separating North 

American and South American-African continents, the 

Yucatan microplate formed its southeastern margin and 

moved southeastward from the Texas-Mexico border 

region. Regional geophysical data and limited well data 

suggest the existence of marginal rift basins beneath 

much of Yucatan, where a carbonate platform formed 

atop rift-stage crust, as in the west Florida province. 
CRU§TAJL ZONE§ 

12:1 Continental Crust 121 Rifted Continental Crust Lilli Rift-Stage Crust ~ Marginal Oceanic Crust [] Oceanic Crust 

Figure 1 (Kiitgord)-Continued. Gulf of Mexico region. 8, Crustal zones. 

The Global Methane Hydrate 

Reservoir-Impact on Petroleum 

Exploration 

Keith A Kvenvolden and Timothy S. Collett 

Gas hydrate is a naturally occurring solid 

composed of rigid cages of water molecules that entrap 

mainly methane. Gas hydrate deposits are globally 

widespread in two distinct settings: (1) offshore, in 

sediments of outer continental margins where water 

44 

depths exceed 300 m, and (2) nearshore and onshore, in 

polar areas where gas hydrate is associated with the 

occurrence of permafrost. The stability of naturally 

occurring gas hydrate is controlled by specific 

requirements of pressure, temperatu.re, and 

concentration of methane in water. The amount of 

methane in gas hydrate in the shallow geosphere 

(subsurface depths of less than about 2,000 m) is very 

large; however, estimates of the amount are speculative 

and range over three orders of magnitude, from 3 X 1015 

to 8X 1018 m3 (1 X 1~ to 3X 108 Tcf). We favor a value of 

about 2X 1016 m3 (7X 1~ Tcf), an estimate that is 
Cll "" 

RIFT- DRIFT 

Bathonian 175 m.a. 

ANOMALY M- 25 

Late Oxfordian 156 m.a. 

GULF OF MEXICO SPREADING CENTER PHASE 

BLAKE 

Bathonian 170 m.a. 

ANOMALY M -21 

Tithonian 150 m.a. 

Figure 2 (Kiitgord). Paleogeographic reconstructions of the continental configurations around the Gulf of Mexico region during the Jurassic. Active plate boundaries 

and plate motions relative to North America are shown. Modified from figure 10 of a 1986 report by Klitgord and Schouten. 
exclusive of methane possibly trapped in reservoirs 

immediately beneath gas hydrate. This estimated volume 

of methane in gas hydrate greatly exceeds the estimated 

volume of methane remaining as a conventionally 

recoverable resource [3X1014 m3 (1X104 Tcf)]. 

The presence of such large quantities of methane 

at such shallow depths should have an impact on 

petroleum exploration and production. Consideration 

has been given to gas hydrate as an unconventional 

energy resource. But at least four factors have deterred 

serious efforts to explore for gas hydrate: (1) insufficient 

information concerning the extent of gas hydrate and its 

reservoir parameters, (2) locations in hostile 

environments of polar regions and the deep sea, (3) no 

agreement on adequate production schemes, and ( 4) no 

economic incentive while conventional gas reserves meet 

global energy needs. Only in the U.S.S.R. at the western 

Siberian Messoyaka gas field has methane been 

recovered from gas hydrate deposits, and this production 

has now been shut-in due to limited pipeline facilities. 

Because gas hydrate occurs at shallow subsurface 

depths, exploration drilling in polar regions and on 

continental margins beyond the shelf will undoubtedly 

encounter these solid gas deposits. The explorationist 

should be aware that certain drilling and production 

problems have already been attributed to the presence of 

gas hydrate in Alaska, Canada, and the U.S.S.R. These 

problems include uncontrolled gas release during drilling 

as well as casing collapse during production. As 

exploration and production activities continue to move 

farther offshore into deeper water and to higher latitudes 

in the Arctic, the frequency of gas-hydrate-related 

incidents is likely to increase. 

Because the global methane hydrate reservoir is 

located so near the surface, portions of this reservoir are 

vulnerable to global climate change. A question of 

current interest concerns possible consequences of 

adding methane, a significant "greenhouse" gas, to the 

atmosphere from destabilized methane hydrate as a 

result of global warming. Models of greenhouse warming 

predict that climatic change will be greatest in the Arctic. 

Permafrost warming and release of methane from gas 

hydrate may already be in progress, but the amount of 

methane that has been or will be released is unknown. 

Any methane that comes from destabilized gas hydrate 

will add to methane that is currently lost to the 

atmosphere as a result of industrial activities involved in 

methane production. Methane from these sources 

augments methane from current biological processes 

resulting in an increase in atmospheric methane 

concentrations during recent time. 

As the search for future energy resources 

continues, gas hydrate will either be eagerly sought or 

46 

assiduously avoided. Either way, the petroleum explorationist will need to be cognizant of this substance. 

Sulfur Isotope Evidence for the Origin of 

Cap-Rock-Hosted Sulfide Deposits, 

Hockley Salt Dome, Texas 

J. Richard Kyle, William N. Agee, Tim W. 

Johnson, and W.C. Shanks, Ill 

The Gulf Coast basin is a dynamic hydrologic 

environment in which mixing of multi-source fluids is a 

plausible mechanism to account for sulfur isotope 

variations of metal sulfide concentrations in salt dome 

cap rocks. Stratiform sulfide laminae have been 

documented within the anhydrite cap rocks of several 

Gulf Coast salt domes (fig. 1). Textural evidence 

indicates that these sulfide laminae represent episodic 

mineralization at the salt/cap rock contact as the cap rock 

formed by sequential underplating. Thus, their metal 

contents and isotopic characteristics can be evaluated in 

terms of a progressive paragenesis from top to base 

representing a relatively long history of rock-fluid 

interactions in the cap rock environment. Reservoirs of 

reduced sulfur and metals evolved during the several 

million year accumulation history of the typical anhydrite 

cap rock. 

The best documented sulfide-bearing cap rock 

mantles the Hockley salt dome in south-central Texas 

where subeconomic Fe-Zn-Pb-Ag sulfide concentrations 

have been defined on the basis of 60 drill holes. Hockley 

is a relatively young diapir with the cap rock believed to 

have developed within the last 45 m.y. Sulfides occur 

throughout the 285-m-thick cap rock and show 

progressive trends with regard to metal ratios and sulfur 

isotope composition. If the Hockley cap rock formed at 

accretion rates of the same magnitude as the Winnfield, 

Louisiana, anhydrite cap rock where paleomagnetic 

studies indicate formation rates of 3-6 m/m.y., then the 

mineralization history at Hockley dome likely lasted 

several million years. Major metal concentrations at 

Hockley occur in a 20-m zone within the central cap rock 

"stratigraphy." The general metal trend is an overall 

increase of Zn relative to Pb downward in the cap rock; 

Ag concentrations are also higher in the lower cap rock. 

These data suggest that the sulfide-precipitating fluid 

became more Zn- and possibly Ag-rich during anhydrite 

cap rock accumulation. 

o34 S values of sulfide minerals within the Hockley 

cap rock range from + 4 to -35%o (n = 100). o

34 S values 

of pyrite within a single drill hole are progressively 

heavier with depth to the approximate middle of the cap 

rock, where the isotopic trend is reversed (fig. 2, p. 48). 
• 

• 

• 

• 

• 

• 

• 

• 

Figure 1 (Kyle). Stratiform sulfide laminae 

(diamonds) in a banded anhydrite cap rock 

core from the Hockley salt dome, Harris 

County, Texas. These pyrite laminae are 

relatively enriched in 32S downward, that is, in 

the paragenetically younger direction, with 

o

34S values changing from --0.3 to -5.0"/oo, 

CDT. 

The inflection point corresponds with a local highly 

mineralized bioepigenetic calcite zone. Relatively heavy 

o

34S values generally correlate with more intensely 

mineralized intervals throughout the cap rock. Analyses 

of closely spaced sulfide laminae (fig. 1) in a 1.5-m 

anhydrite intercept indicate a range of o34 S values from 

-0.3 to -7.9%o (n =23). Vertical trends and clustering of 

values for adjacent !amine suggest that local/temporal 

variations affected the sulfur reservoir at this scale. 

The complementary metal and o34 S data indicate 

that two isotopically distinct sulfur components were 

involved in cap rock sulfide mineralization. An isotopically light H2S is attributed to bacterial reduction of 

aqueous sulfate derived from dissolution of anhydrite cap 

rock (o34S = + 16± 1 %o ). The correlation between 

intensity of sulfide mineralization and sulfide o

34 S 

indicates a genetic relationship between the generation of 

47 

heavy H2S and the supply of metals by relatively hot, 

deep-source formation waters. Heavy H2S could have 

been supplied along with metals in these formation 

waters. Conversely, if petroleum was present in the 

formation waters, then thermochemical reduction of cap 

rock sulfate could produce isotopically heavy H2S . 

The highly mineralized intervals with heavy o

34S 

values are interpreted to represent a sustained supply of 

relatively hot, deep-source fluids to the cap rock 

environment. These events resulted in a greater 

contribution of heavy H2S to the mixed sulfur reservoir, 

either through extrinsic supply or by local thermochemical production of H2S. Large volumes of heated metalliferous formation waters also could indirectly affect the 

supply of isotopically light H2S. Episodic introduction of 

~ 100 oc fluids would periodically decimate the bacterial 

population. Heavy H2S would dominate the sulfur 

reservoir until the salt dome environment returned to 

lower temperatures for bacteria regeneration. 

The preferred mineralization model for Hockley 

dome proposes that warm metal-bearing formation 

waters migrated up the salt dome flanks and mixed with 

ambient cool meteoric waters containing isotopically 

light H2S produced by bacterial activity. Introduction of 

metalliferous fluids, perhaps episodically released during 

basin dewatering, overwhelmed the light H2S component 

by the combined effects of supplying heavy H2S and 

suppressing local bacterial H2S production. The trend of 

progressively heavier o34S values of sulfide laminae 

toward the middle of the cap rock along with high metal 

concentrations suggests that basin-derived fluids reached 

a maximum during the middle history of anhydrite cap 

rock accumulation. Biogenic H2S then began to 

dominate the mixed sulfur reservoir resulting in the trend 

toward relatively light o

34S values of the scattered 

mineralized zones to the present cap rock/salt contact. 

Acknowledgments: This research was partly 

conducted during a University Research Institute Faculty 

Research Assignment to RK; additional support was 

provided by NSF grant EAR-8709319. 

Quality Parameters of Permian 

(Gondwana) Coal, Khalaspir, Bangladesh 

E.R. Landis, M.N. Islam, and Hal Gluskoter 

A recently completed exploratory drill hole in the 

northwestern part of Bangladesh penetrated more than 

500 feet of coal-bearing strata in the Gondwana 

sequence of Permian age. The hole was drilled by the 

Geological Survey of Bangladesh at a site selected on the 

basis of geophysical interpretation of gravity 

measurements. Coal of Permian age is now known to be 
Metals (wt %) 

0 10 20 30 

300 

HH 2 

D Fe 

-p ++ + + • ~ Pb + Zn 

++ 

p + 

400 

500 - ++ 

+ ~ 

* 

600 g - + 

.c. 

a ~ *+-= 

Q) 

0 700 - ..L 

+ 

~ + 

b:-. + 

+ 800 

~ ~ + 

+ 

900 - + 

+ 

+ 

1000 - + I I I I 

-40 -30 -20 -10 0 10 

Figure 2 (Kyle). Histogram showin~ metal content of cap rock drill hole HH2 

at Hockley dome compared with o3 S composition ( +) of selected stratiform 

sulfide laminae. Note general correlation of relatively heavy o

34S values with 

greater metal abundances. 

present in three different areas of northwestern Bangladesh, and other potential coal areas await exploration. 

Coal is not presently mined in Bangladesh but might in 

the future constitute a valuable energy resource for the 

country. 

48 

A total of 41 core samples of coal and associated 

coaly rocks from 12 different coal beds were selected 

megascopically to represent grade and type differences in 

the coal. The samples were collected, packed, and 

shipped to an analytical laboratory in a standard manner. 
The coal beds that were sampled range in thickness from 

less than 2 feet to almost 50 feet. The uppermost coal bed 

occurs at a depth of about 935 feet. Further exploration 

is needed to determine the lateral extent of the coal beds. 

Preliminary results from the standard coal 

analytical procedures indicate that according to ASTM 

Standards, 31 of the individual samples have an apparent 

rank of medium-volatile bituminous coal, and the other 

samples have apparent ranks ranging from high-volatile 

A bituminous to anthracite. The individual coal samples 

range in ash content from 7.6 percent to almost 50 

percent: two-thirds of the samples contain less than 25 

percent ash and almost half contain 15 percent or less 

ash. Sulfur content ranges from 0.26 percent to 1.7 

percent: three-quarters of the samples contain less than 1 

percent sulfur. The Free Swelling Index of individual 

samples ranges from 0 to 7.5: the index of 26 samples is 

2.5 or less, and 14 of those samples had an index of 1.0. 

The Hardgrove Grindability Index of the samples ranges 

from 43 to 59. 

Weighted (by thickness) average analyses for coal 

beds or benches of thick coal beds, were calculated. ' . Almost all fall in the apparent rank category of mediUmvolatile bituminous coal, have medium (less than 15 

percent) to high ash contents, and have low (1 percent or 

less) to medium (less than 3 percent) sulfur contents. 

The coal beds are thicker and contain less ash in the 

upper part of the coal-bearing sequence. For example, 

two thick beds (about 45 and 50 feet thick, respectively) 

in the upper 116 feet of the Gondwana sequence have a 

weighted average analysis, on the equilibrium moisture 

basis, of 2.6 percent moisture, 13.9 percent ash, 1.0 

percent sulfur, 24.3 percent volatile matter, and 59.2 

percent fixed carbon, and a heat value of 12,519 Btu/lb. 

The available information indicates that the coals 

of the Khalaspir area are suitable for most or all forms of 

thermal conversion, such as generation of electricity. An 

undefined but probably smaller part of the resource 

might also be suitable for use in the manufacture of 

metallurgical coke. 

Thermal Evolution of the Upper 

Cretaceous Fruitland Formation, San 

Juan Basin, Colorado and New Mexico 

Ben E. Law 

The source of heat during the thermal evolution of 

the coal-bearing Upper Cretaceous Fruitland Formation 

in the northern part of the San Juan Basin of Colorado 

and New Mexico has been the subject of controversy for 

many years. In recent years, the successful exploitation of 

gas from coal beds in the San Juan Basin has revived the 

49 

controversy and provided additional impetus to learn 

more about the thermal history of these coal beds. Nearly 

all previous work dealing with the thermal history of the 

Fruitland has alluded to volcanic activity in the nearby 

San Juan Mountains to the north as a probable source of 

heat. However, based on the interpretations of timetemperature modeling and thermal maturity patterns 

derived from a recently completed project of thermal 

maturity mapping in the San Juan Basin, the high levels 

of thermal maturity in the northern part of the San Juan 

Basin are postulated to be due to a deep, localized source 

of high heat flow in conjunction with convective heat 

transfer associated with vertically directed fluid flow. 

There does not appear to be any evidence supporting the 

notion that the observed levels of thermal maturity are 

due to a heat source located in the San Juan Mountains. 

Mean random vitrinite reflectance (Rm) values of 

coal beds in the Upper Cretaceous Fruitland Formation 

in the San Juan Basin of Colorado and New Mexico 

range from 0.42 percent in the southern part of the basin 

to 1.54 percent in the northern part of the basin, wher~ a 

northwest-trending irregular-shaped area of h1gh 

thermal maturity occurs. North of the area of high 

thermal maturity, in the subsurface and in outcrops, Rm 

values in the Fruitland decrease to less than 1.0 percent. 

Isoreflectance lines drawn on structural cross sections 

intersect dipping bedding planes at large angles at either 

end of the cross sections where they cross the basin's 

steeply dipping monoclinal rims. In the central part of ~he 

basin, isoreflectance lines are far above the same beddmg 

planes on these cross sections. This relationship between 

structure and thermal maturity indicates that the levels of 

thermal maturity were achieved after structural 

deformation of the basin. 

Rm profiles of wells drilled through Cretaceous 

and Tertiary rocks in the basin are commonly nonlinear 

with two to four segments. In the southern, less mature 

part of the basin, nonlinear Rm well profiles have two 

segments, an upper steep-sloping segment and a lower 

moderate-sloping segment. The intersection of these 

segments occurs at Rm values ranging from 0.55 to 0.60 

percent. In the northern, more mature part of the basin, 

where Rm values of the coal-bearing Fruitland 

Formation are greater than 0.8 percent, nonlinear Rm 

well profiles have as many as four segments, in 

descending order: a moderate-sloping segment, a nearly 

vertical steep-sloping segment, a low-sloping segment 

through the coal-bearing Fruitland Formation, and a 

moderate-sloping segment. In the area of high thermal 

maturity, Rm gradients through the coal-bearing Fruitland are high, ranging from 1.0 to 1.5 percent/1,000 ft, 

compared to gradients in overlying and underlying rocks 

that range from 0.01 to 0.30 percent/1,000 ft, 

respectively. These gradients most likely represent the 

combined effects of contrasting thermal conductivities 
associated with lithologic variations and differences in 

heat transfer processes (conductive vs. convective). In the 

area of low thermal maturity there is no distinct Rm 

gradient coincident with the coal-bearing Fruitland, 

perhaps due to the facilitation of heat transfer through 

the coal beds by the relatively large amounts of moisture 

contained in low-rank coals. 

Time-temperature modeling of a few wells in the 

San Juan Basin indicates that present -day heat flow is 

insufficient to account for the measured levels of thermal 

maturity. The modeling shows that heat flow reached a 

maximum of about 200 mW/m2 during Eocene and 

Oligocene time. Furthermore, in order to match the 

nonlinear Rm well profiles, artificially high thermal 

conductivity values must be assigned to nearly all the 

stratigraphic units. The unreasonably high thermal 

conductivity values could be interpreted as evidence of 

heat transfer by vertically directed fluid flow. 

Identified Petroleum Systems Within the 

United States-A 1990 Status Report 

Leslie B. Magoon 

Exploration and resource assessment can be made 

more efficient if the processes responsible for petroleum 

occurrence can be studied in the context of a genetic 

unit-the petroleum system. Such a study is intermediate 

between basin analysis and play or prospect evaluation. 

Basin analysis emphasizes structural depressions and the 

included sedimentary rocks, regardless of the relation to 

any petroleum deposit; study of the petroleum system 

emphasizes the genetic relation between a particular 

source rock and the resulting petroleum accumulations; 

play evaluation emphasizes structural and stratigraphic 

reservoir trends; and prospect evaluation emphasizes 

individual traps. Economics are less important in a basin 

analysis or in a petroleum system study than in a play or 

prospect evaluation. 

A petroleum system encompasses a hydrocarbon 

source rock and all generated oil and gas accumulations, 

and includes all those elements that are essential for an 

oil and gas deposit to exist. Petroleum includes 

concentrated occurrences of any of the following: 

thermal and microbial natural gas found in conventional 

reservoirs as well as in gas hydrate, tight sandstone, 

fractured shale, and coal; condensates; crude oils; heavy 

oils; and solid bitumen found in siliciclastic and 

carbonate reservoir rocks. System describes the 

interdependent geologic elements that create oil and gas 

accumulations. These elements include a petroleum 

source rock, migration path, reservoir rock, seal, trap, 

and the geologic processes that create each element. All 

50 

these elements must be correctly placed in time and 

space for a petroleum deposit to occur. 

The stratigraphic, areal, and temporal extent of a 

petroleum system is specific. The system includes the 

following stratigraphic units: a petroleum source rock, 

rocks through which migration has occurred, a sealed 

reservoir rock (trap), and the rock overburden 

(representing time and temperature) required for 

maturity. The areal extent of the petroleum system is 

defined by a line that circumscribes the mature source 

rock and all oil and gas deposits, conventional and 

unconventional, originating from that source. The events 

of a petroleum system are defined by two timespans, the 

duration time and the preservation time. The duration of 

a petroleum system is the time it took to deposit the basic 

elements and generate the hydrocarbons, or to form the 

system. The preservation time is the length of time that 

some hydrocarbons within the system have been 

preserved in the geologic record. 

The system nomenclature combines the geologic 

names of the source and reservoir rock units, and also 

expresses a level of certainty. For example, the TuxedniHemlock(.) is a petroleum system in the Cook Inlet, 

Alaska. The level of certainty is the likelihood that a 

particular hydrocarbon accumulation originated from a 

particular source rock. Petroleum systems are classified 

by using criteria such as source- and reservoir-rock type 

and the complexity of their geologic history. 

The list of petroleum systems within the United 

States has been revised and expanded to include new 

information published since the last tabulation in 1988, in 

which 119 systems were identified. Presently 130 

petroleum systems have been identified, of which 89 are 

purebred (structurally simple) and 41 are hybrid 

(structurally complex). Of 12 possible categories, the 2 

most common systems are in the purebred siliciclastic 

category and have either type II (32) or type III (19) 

source rocks (rocks containing type II or III organic 

matter). Presently, all hybrid carbonate systems contain 

type II source rocks. Siliciclastic reservoirs (90) occur 

more than twice as often as carbonate reservoirs (40). 

The most common source rock is type II (73 ), followed 

by type III (41); the least common source rock is type I 

(16). 

By characterizing petroleum systems using these 

and other geologic criteria, various elements of each 

system can be more clearly identified and compared to 

determine their efficiency in the generation, migration, 

and trapping of hydrocarbons. Characterizing the 

efficiency of each petroleum system and of each element 

within it will help focus research, resource assessment, 

and exploration programs. 
Deep-Water Fan Deposits, Gulf of 

Mexico-Seeing Through Salt 

Seismically 

Robert E. Mattick and Frederick N. Zihlman 

The hypothesis that the Sigsbee Escarpment in the 

northwestern Gulf of Mexico is not associated with 

deep-rooted structural uplift, but is an expression of 

horizontally intruded and (or) extruded tongue-shaped 

salt lobes covered by a veneer of upper Pleistocene 

sediments less than 1,000 m thick, is supported by at least 

four lines of evidence from seismic data: (1) the top and 

bottom of the inferred salt mass are marked by strong 

reflections; (2) a distinct velocity inversion can be 

measured at the base of the inferred salt mass; (3) 

seismic horizons recorded on the rise continue, without 

change in character, into the interior of the slope beneath 

the inferred salt mass; and ( 4) the thickness of the 

inferred salt tongue is about equal to the height of the 

escarpment above the sea floor. 

Formation of the Sigsbee Escarpment apparently 

influenced construction of a 2,000-m-thick deep-water 

fan complex that is mapped on the rise at the base of the 

escarpment. The fan complex is of Pleistocene age. The 

oldest fan units may have been derived from sediments 

shed from an early escarpment located landward of the 

Sigsbee Escarpment. The short-lived, early depocenters 

of turbidite deposition appear to have migrated back and 

forth (in an east-west direction) for distances in excess of 

200 km. During and following formation of the Sigsbee 

Escarpment, which may have involved two phases of salt 

intrusion or extrusion during late Pleistocene time, the 

principal depocenter of turbidite deposition has migrated 

about 250 km westward. 

Some of these fan deposits, at water depths of 2.5 

km and buried beneath 2-3 km of salt and Pleistocene 

sedimentary rocks, may be potential reservoirs for oil and 

gas. 

Subsidence, Eustasy, and 

Climate-Controls on Coal and Clastic 

Facies Architecture, Cretaceous of 

Western United States 

Peter J. McCabe, Robert D. Hettinger, Mark A. 

Kirschbaum, J. David Sanchez, and 

Keith W. Shanley 

In order to develop more predictive models of the 

geometry and quality of coal deposits, it is important to 

better understand the roles of subsidence, eustasy, and 

51 

climate in controlling coal accumulation. These same 

parameters also control clastic facies architecture. As 

part of a major study of the controls on Cretaceous coal 

accumulation, high-resolution facies studies are being 

carried out on outcrops of coal-bearing strata in various 

locations in the western United States. Lessons learned 

from these studies can be applied not only in coal 

exploration but also in oil and gas exploration for 

sandstone reservoirs. 

Outcrop studies in the Kaiparowits Plateau area of 

southern Utah allow examination of fluvial deposits, 

shoreface sequences, and coals within a variety of 

systems tracts. Major coal deposits are present in both 

the Dakota Formation and the John Henry Member of 

the Straight Cliffs Formation. The Dakota Formation, of 

Albian to Cenomanian age, is part of a transgressive 

systems tract which separates the underlying Jurassic 

strata from the overlying marine Tropic Shale. Coal 

zones in the Dakota can be traced over several tens of 

kilometers, and individual seams are locally as thick as 

5.5 m. Ribbon-shaped channel sandstones, interpreted as 

anastomosed river deposits, are present between the coal 

zones. Other facies include thin rippled sandstones, 

rooted mudstones, and fossiliferous mudstones which are 

interpreted respectively as crevasse splay, overbank, and 

lacustrine deposits. These clastic deposits are thought to 

have been introduced during periods of major river 

avulsion into the mire environments. By contrast, the 

John Henry Member was deposited as an early highstand 

systems tract during the Coniacian to early Campanian. 

Coals of this member lie within a 25-km-wide band that 

parallels the paleoshoreline trend; coal seams are locally 

as thick as 5 m. To the northeast in this systems tract are 

vertically stacked shoreface sandstones; to the southeast 

are vertically aggraded fluvial deposits. The latter consist 

of tabular meanderbelt sandstone bodies lying within 

thick overbank mudstones. 

In contrast to the Dakota and John Henry, the late 

highstand systems tracts of the Turonian Tibbet Canyon 

Member and lower part of the Smoky Hollow Member of 

the Straight Cliffs Formation contain coals that are thin 

and laterally discontinuous. Shoreface deposits show a 

marked forward-stepping pattern and are overlain by 

tidal channel and meandering river deposits. Coals are 

not associated with the braided river deposits of the 

upper part of the Smoky Hollow Member or the Campanian Drip Tank Member of the Straight Cliffs 

Formation, which are interpreted to have formed in 

broad incised valleys above sequence boundaries. 

The nature of the mires in which the coals 

accumulated appears to be important in controlling the 

facies architecture of some of the associated clastics. The 

ribbon-like nature of the sandstones in the Dakota may 

be due to the style of avulsion into the vegetated mires. 

During the Coniacian and Santonian, however, the 
climate appears to have favored the formation of raised 

mires. The elevated nature of these mires would have 

restricted the landward inundation of marine waters 

during transgressions. The mires may, therefore, have 

been a critical element in determining the unusual 

vertical stack of more than 250 m of shoreface deposits 

within the John Henry Member. 

Characteristics of Coal-Bearing Strata in 

Tertiary Basins, Based on Integrated 

Sedimentary and Structural Field Studies, 

Southwestern Montana 

J.W. M'Gonigle, M.H. Hait, Jr., and 

W.J. Perry, Jr. 

The Medicine Lodge (ML) and Horse Prairie 

(HP) topographic basins, which are partly separated by 

the north-trending Maiden Peak spur, are bounded by 

the Tendoy and Beaverhead Mountains in the eastern 

part of the Cordilleran thrust belt. The similarity of 

deposits in both basins, depicted in restored structuralstratigraphic sections, indicates that the original 

depositional basin extended far beyond the present ML 

and HP basins. Eocene(?) to mid-Miocene strata 

deposited in the original basin are coal bearing, whereas 

younger strata are not. 

Tertiary deposition began with the accumulation of 

as much as 900 m of Eocene volcanic rocks, which were 

then locally eroded before the start of Eocene(?) and 

Oligocene fluvial and lacustrine sedimentation. 

Limestone and shale deposits in the southern part of the 

ML basin represent a >300-m-thick lacustrine facies 

that interfingers northward with a marginal-lacustrine 

facies of shale, some conglomeratic sandstone, and carbonaceous shale and coal. After local uplift and erosion 

of some of these sediments, fan-delta and delta plain 

deposits (700-900 m thick) advanced during the Oligocene(?) and Miocene into the southern margins of the 

lake. Source area for the deltas was a highland to the 

south, as evidenced by the types of clasts in the 

conglomerates. Coal-forming environments developed 

on inactive fan-delta platforms and in inter-distributary 

depressions. Thick (1,300 m) mud-rich lacustrine 

deposits subsequently dominated basin sedimentation. A 

second influx of coarse clastics, of probable late early 

Miocene age, from Tertiary, Archean, and Mesozoic 

sources, formed fans hundreds of meters thick. 

Ephemeral coal-forming environments developed lateral 

to the fans. 

The eastward tilt of Eocene to mid-Miocene units 

suggests that considerable low-angle westward extension 

52 

occurred after the original basin was largely filled. These 

tilted beds dip into low-angle, westward-dipping 

detachment surfaces exposed in the western Tendoy 

Mountains. In the southern HP basin, tilted lower 

Miocene beds are overlain by thick, massive, middle 

Miocene mudstone deposits which dip slightly to the 

west. We suggest that extension of the HP and ML basins 

took place after early Miocene and prior to middle 

Miocene time. In addition, exposure and erosion of the 

Maiden Peak spur and the Tendoy Mountains were 

probably enhanced if not caused by isostatic uplift 

accompanying tectonic denudation. 

Coal-bearing parts of the Tertiary basins in this 

area: (1) appear to have been formed in relatively large, 

mud- and carbonate-rich Eocene(?) to mid-Miocene 

lacustrine basins that were subject to incursions of 

coarser clastic debris, and (2) occur in association with 

thick facies sequences, suggesting that deposition took 

place in relatively stable, long-lived basins. Most of the 

coal-bearing strata of this age would probably have been 

tilted by regional westward extension. Post-early 

Miocene basins were smaller, and therefore probably 

more susceptible to minor structural and sedimentary 

disturbances that, irrespective of climatic conditions, 

tended to inhibit the development of widespread coal 

deposits. 

Geochemical Evaluation of Gas-Bearing 

Coals with Respect to Maturity, Upper 

Cretaceous Fruitland Formation, San 

Juan Basin, New Mexico and Colorado 

G.E. Michael, B.E. Law, and D.E. Anders 

Coal units from the Fruitland Formation of the San 

Juan Basin were analyzed for bulk compositional and 

biomarker changes relative to maturity. Coal in the 

Fruitland ranges in maturity from volatile B bituminous 

to medium-volatile bituminous. (Rm values range from 

0.42 to 1.54 percent.) Forty-six samples were analyzed by 

Rock-Eval pyrolysis and vitrinite reflectance (Rm). 

Fifteen samples were chosen for further analysis of 

sterane and terpane biomarkers and saturated and 

aromatic hydrocarbon fractions. 

Fruitland coal is relatively hydrogen rich and 

oxygen poor. The hydrogen indexes (HI) (S2/TOC) are 

primarily between 100 and 350 and oxygen indexes 

(S3/TOC) range between 10 and 45. When plotted 

against Rm both S1/TOC and S1/(S1 + S2) 
(transformation ratio) show the onset of hydrocarbon 

generation at Rm 0.70 percent (Tmax 442) with 

maximum generation in the Rm 0.80 to 0.85 percent 

range (Tmax 447 to 451). The hydrogen index decreases 

linearly with increasing Rm. 

At low maturities up to 0.75 percent Rm, n-alkanes 

range from C25 to C31 with strong odd/even 

predominance, typical for immature type III organic 

matter. Above 0.75 percent Rm, odd/even predominance 

is lost and distributions become increasingly unimodal 

toward lower molecular weight n-alkanes. The pristane 

(Pr) :phytane (Ph) ratio decreases linearly with increasing 

Rm. The Pr:n-C17 ratio also decreases, however, in a 

logarithmic relationship with increasing Rm. Four 

mature samples were nearly devoid of n-alkanes and 

therefore did not fit into the n-alkane maturity trend. 

These differences could be due to heterogeneous organic 

matter type in the coals, to variation in expulsion as a 

result of fracturing, or to biodegradation. The samples 

which do not fit the n-alkane maturity trend are from 

areas of anomalously high gas production. 

Aromatic hydrocarbon distributions show the loss 

of triaromatic pentacyclic compounds at maturity greater 

than 0.60 percent Rm, whereas lower molecular weight 

bicyclics and tricyclics continue to remain at higher 

maturity. Triaromatic pentacyclics in the C25 to C27 

range constitute a large portion of aromatics in the low 

maturity samples from the Fruitland coal. Methylphenanthrene ratios were used to determine the maturity 

in Rm equivalent values. 

Pentacyclic terpanes are present in higher 

concentration relative to steranes at all levels of maturity 

in the sample suite. The relative amount of rearranged 

steranes to regular steranes was low in all the samples, 

even at high maturity. The sterane maturity reactions 

reach completion between 0.75 and 0.80 percent Rm. 

Complete conversion of monoaromatic steroids to triaromatic steroids is achieved by 0.75 percent Rm, a process 

which often does not occur until 1.00 percent Rm. High 

molecular weight triaromatic steroids disappear by 0.93 

percent Rm, leaving only low molecular weight triaromatics. 

Hopane maturity parameters reach equilibrium 

around 0.90 percent Rm in the sample suite. The source 

and (or) maturity parameter Tm:Ts ratio varied unsystematically with respect to maturity. The ratio of tricyclic 

to pentacyclic terpanes varies inconsistently with 

maturity. 

The extractable hydrocarbon yields range from 

5,600 ppm to 40,000 ppm, which indicates good potential 

for oil generation. Minor amounts of condensate have 

been found associated with the Fruitland Formation and 

are likely generated from adjacent coal beds. 

53 

Applications of Expert Systems and 

Geographic Information Systems to Basin 

Characterization-Case Study for the San 

Juan Basin, New Mexico 

Betty M. Miller 

The U.S. Geological Survey (USGS) is currently 

applying geographic information systems (GIS) 

technology to develop a geologic knowledge base that will 

provide the framework for an integrated basin analysis 

for the San Juan Basin. GIS technology involves the 

integration of mapping and data-base functions that 

enable the user not only to integrate and manipulate 

spatial (coordinate) data with attribute (thematic) data in 

order to combine complex geographic, geologic, and 

geophysical data sets into resultant overlay and 

composite maps, but also to conduct multivariate 

exploratory data analysis and to access a variety of 

options for analyzing these data bases. 

The analysis of a sedimentary basin requires a 

multidisciplinary approach drawing on many areas of 

geologic expertise supported by the integration and 

analysis of large volumes of multivariate spatial data. 

One such method being investigated for analyzing 

sedimentary basins in conjunction with GIS is the 

application of expert systems techniques that simulate 

the logic of basin experts to model geologic concepts, to 

document and analyze geologic attributes, and to 

interpret the history of a sedimentary basin. This 

knowledge of the geologic settings, histories, and 

processes characterizing these basins is important for 

predicting the occurrence of oil and gas, uranium, oil 

shale, coal, phosphate, and many other essential energy 

and mineral resources. 

The San Juan Basin, a 13,500-mi2 Laramide 

structural basin in northwestern New Mexico, was chosen 

for the initial pilot project. The basin encompasses a 

maximum of > 15,000 feet of Paleozoic to Eocene 

sedimentary rock and contains economic deposits of 

natural gas, oil, coal, and uranium. Successful 

exploration in this basin requires an understanding of the 

complex stratigraphy and structure controlling the 

distribution of these resources. 

Initially the basin analysis project focuses on the 

integration of the multivariate data bases for merging 

large volumes of surface and subsurface data. GIS 

technology applied to the San Juan Basin is used to 

establish a three-dimensional perspective of the basin's 

fundamental stratigraphic and structural framework and 

to aid in the identification of its temporal and tectonic 

relationships relative to origin and occurrence of its 

resources. Digital Jata bases being used for surface 

mapping include: the Digital Elevation Models (DEMs) 
SUBSURFACE 

Figure 1 (B. Miller). Three-dimensional sedimentary basin analysis. 

for terrain elevations; Digital Line Graphics (DLGs) for 

planimetric information on boundaries, transportation, 

and hydrography; the U.S. Public Land Survey System; 

and Land Use and Land Cover (LULC) data. Additional 

data bases used for surface mapping include surficial 

geology, locations of oil and gas wells, well status, and oil 

and gas fields. 

Information data bases providing the attributes for 

subsurface mapping include those for geologic maps such 

as structure-contour, isopach, and facies maps for the 

major oil- and gas-producing formations within the basin; 

cross sections; paleogeographic reconstructions; geophysical maps; and geochemical maps showing organic 

richness and maturity relative to source bed distribution. 

The GIS manipulates data such that an overlay of 

data layers can produce a new layer of information, or 

data can be merged from multiple maps into single new 

maps. (See figure 1.) Current GIS technology and 

mapping software being used for the three-dimensional 

analysis of the San Juan Basin includes the ARC/INFO 

system (Environmental Systems Research Institute) 

using the PRIME computer and the Interactive Surface 

54 

Modeling (ISM) software package (Dynamic Graphics, 

Incorporated). The Petroleum Information-Well History 

Control System (PI-WHCS) well data base provides one 

of the major sources for well information (Petroleum 

Information Corporation). 

Expert systems techniques included in the basin 

study are used to develop knowledge-based expert 

systems documenting the basic geology and geologic 

concepts that characterize a basin; provide a diagnostic 

tool to understand and predict the occurrence of energy 

and mineral resources on the basis of a basin's geologic 

history, including the interaction between tectonics and 

sedimentation; and provide an "intelligent" data 

management system, an "intelligent" system for 

processing and understanding spatial data relationships, 

an efficient system for exploring and viewing spatial data 

bases, and methods and algorithms for exploratory data 

analysis and data-base queries. 

GIS technology, when integrated with an expert 

advisor system, provides new tools for innovative 

research in geologic interpretation, for updating 

information data bases, for developing new concepts in 
basin analysis, and for new resource appraisal 

methodology. GIS and expert systems technologies can 

document and preserve invaluable, complex, and very 

large knowledge bases that are essential to the evaluation 

of energy and mineral resources. 

This project will demonstrate the feasibility of 

applying GIS and expert systems techniques to building 

data bases and making these data bases available to the 

USGS and other resource management agencies. 

Data Analysis and Display Techniques of 

the National Coal Resources Data 

System, a Geologic Data System 

William G. Miller, Kathleen K. Krohn, Carol L. 

Molnia, and Susan J. Tewalt 

The National Coal Resources Data System 

(NCRDS) of the U.S. Geological Survey is an integrated 

GIS digital system that accesses a master data base and a 

suite of 2- and 3-dimensional mapping, display, and 

statistical capabilities for data analysis and visualization. 

Currently the system operates on a network with 

main nodes in Reston, Va., and Denver, Colo., and is 

accessed by scientists and other coal experts within and 

outside the USGS. Twenty-two State geological agencies 

have cooperative agreements with NCRDS and access 

the system from remote sites via commercial and USGS 

telecommunications networks. Software modules 

operate on a range of equipment platforms: three Sun 4 

servers, minicomputers (Prime), desktop UnixXwindow-based workstations, microcomputers (IBMPC compatibles), and mainframes. Development of 

software and the acquisition and integration of hardware 

are ongoing to provide coal geologists with the means to 

analyze multiple coal-data elements and to create a 

variety of map products with enhanced flexibility and 

interactivity. 

The data-base information includes: stratigraphic 

descriptions and coal quality data (trace element, Btu, 

ash, and sulfur analyses) located by latitude and 

longitude, as well as summary files (coal tonnage and 

coal quality information) located by geographical area. 

The basic geologic data are used primarily to model coal 

deposits and analyze resource estimates in 2- and 3-

dimensional maps and diagrams. 

Necessary and desirable procedures for NCRDS 

include using a combination of both in-house developed 

software and commercial software; not all requirements 

for USGS coal resource assessment techniques are fully 

addressed by commercial vendors. At present NCRDS 

has the following programs available for use for resource 

assessment and mapping: USGS's GARNET; Dynamic 

55 

Graphic's Interactive Surface Modeling (ISM); a USGS 

version of Krieging geostatistics; and aspects of ARCINFO, a geographic information system (GIS). Image 

analysis techniques are being investigated for their 

applicability to coal geology analysis. 

Coal resource tonnage calculation provides an 

example of how multiple digital mapping software 

capabilities are used. First, the data specified are gridded 

and contoured. Then the areas of interest are defined by 

(1) digitized boundaries (outcrop, geologic, geopolitical); 

(2) boundaries constructed from contoured data at a 

chosen interval (such as thickness, sulfur, overburden 

from digital elevation models (DEMs), structure); and 

(3) the intersection of the boundaries of interest (such as 

the area where a coal bed has a thickness of 14-28 in., a 

sulfur content less than 1 percent, and an overburden 

thickness less than 200 ft). Finally, the tonnage of coal 

meeting specified criteria is calculated. These techniques 

have been used successfully in a variety of projects of 

various scales, including lease tract studies, quadranglebased studies, and various county studies, as well as coal 

basins and regions. 

The main advantages of digital graphical analysis of 

geologic data, in contrast to manual methods, are that (1) 

many data elements can be examined efficiently by digital 

techniques, and (2) with these digital techniques 

available, multiple questions can be asked in new 

combinations of data that otherwise would be impossible 

or impractical to address. 

Stratigraphic Cross Sections of Upper 

Cretaceous Rocks Across the San Juan 

Basin, Northwestern New Mexico and 

Southwestern Colorado 

Cornelius M. Molenaar and James K. Baird 

Detailed stratigraphic cross sections are excellent 

for visually portraying facies relations and to help 

interpret the depositional history of sedimentary basins. 

The time-transgressive Upper Cretaceous rock units of 

the San Juan Basin of northwestern New Mexico and 

southwestern Colorado, which have large-scale facies 

changes, are especially well suited to this type of analysis. 

The San Juan Basin, once part of the larger 

Western Interior basin, is an early Tertiary structural 

depression in which a thick section of Cretaceous rocks is 

preserved. In and flanking the basin, these rocks contain 

large reserves of gas, oil, and coal; the coals contain large 

reserves of coal-bed methane, which are currently being 

developed and produced. The extensive exposures of 

Cretaceous rocks rimming the basin, the large number of 

drill holes (20,000 ± ), and the relatively simple structure 
1'+------,----------------- 240 KILOMETERS (150 miles)-------------,-------~:,..j. NEI 

~~-------------------SAN JUAN BASIN --------~N~EW~M~EX~IC~O~....::C:.:;:O:!:.:LO~R:_:A~DO~----o-l 

: SAN JUAN MTNS 

I Ou.a~go , : 1 Pagosa TAH COLO. Sprin s ARiz':t'N..,Tx ·· ---- !:!!!.11. : f I I Farmingto n I 

: I I SAN I JUAN 

: I I I BASIN : 1 Cuba 

I I 

dattuP 

! 

METERS FEET 

500 

1,500 

400 

300 1,000 

VERT. EXAG. ~ 85 

200 

500 

100 

0 0 

EXPLANATION 

~ Nonmarme rocks 

- Marine and coastal-barrier sandstone 

c=J Mari ne shale and siltston e 

~-:; Calcareous shale 

Time ma~ker bed, e.g., benton1te , calcareous 

Arroyo Tongue of Mancos Sh 

f+------BLANCO GAS FIELD-----.-, 

Figure 1 (Molenaar). Northeast-trending stratigraphic cross section showing Upper Cretaceous rocks of the San Juan Basin 

of New Mexico and Colorado. Location of line of section is shown on inset map in upper left corner. Control for section is based 

on detailed measured outcrop sections and well-log interpretation. Cen. =Cenomanian, Turon.= Turonian, Con.= Coniacian, 

Maastricht.= Maestrichtian (now spelled Maastrichtian). 

of the basin make this area ideal for stratigraphic 

analyses through the use of stratigraphic cross sections. 

Upper Cretaceous rocks of the basin, which are as 

much as 6,500 ft (1,980 m) thick, comprise a classic 

sequence of intertonguing marine and nonmarine facies. 

Geophysical logs from closely spaced drill holes 

throughout most of the basin provide data for detailed 

rock-unit correlations which can be made by using 

numerous time marker beds within the marine shale 

sections. These marker beds provide a time framework 

for construction of cross sections that show (1) diachronism and stratigraphic rise of shoreface-sandstone bodies 

associated with the four major transgressions and 

regressions of the Western Interior seaway within the 

basin, (2) shelf to very low angle slope ( < 0.25") to 

56 

basinal topography, (3) the Coniacian (basal Niobrara) 

unconformity, (4) low-amplitude paleostructural 

features, and (5) low-relief differential compaction 

features associated with lateral heterogeneities in sandshale sections. 

Variation of Modern Siliciclastic Turbidite 

Systems and Basin SettingsImplications for Reservoir Development 

C. Hans Nelson 

Studies of a number of turbidite system elements 

(conduits of canyons and deep-sea channels, depositional 
bodies of fans and aprons, connecting channels of 

channel-levee complexes and axial channels) show that 

no single submarine fan model suffices to describe 

reservoir characteristics (table 1, p. 58). Slope canyons 

and deep-sea channels provide point-source conduits for 

channelized fans. Fans can vary from smaller ( = < 100 

km) sand-rich fans with good vertical-continuity 

reservoirs in short channels and mid-fan lobes to larger 

(= > 100 km) mud-rich fans with reservo~r beds .in 

extensive channel floors, but unknown reservOir potential 

in thin sheetlike distal sand lobes. Multiple slope failures 

and numerous local debris chutes can feed base-of-slope 

aprons that lack significant development of channels and 

depositional lobes, but consist of sediment gravity flow 

and turbidite sheet-flow deposits. Aprons also can vary 

from smaller (few kilometers) sand-rich wedges with 

apparent good reservoir continuity throughout to larger 

(tens of kilometers) mud-rich lobes with poor continuity. 

Channel-levee complexes, axial channels, canyons and 

deep-sea channels may be associated with aprons and 

fans. Channel-floor facies in any of these connecting or 

conduit turbidite systems may provide good sand-rich 

reservoir beds (table 1). 

Turbidite-system reservoirs in basin settings may 

vary from a simple case such as the mud-rich Astoria Fan 

filling the trench off Oregon to the complex example of 

the western Mediterranean Valencia Trough, which 

contains prograding slope canyons, channel-levee 

complexes, aprons, a deep-sea channel, and a submarine 

fan that form a connected series of coeval turbiditesystem elements (table 1). Present-day trench floors and 

rift basins also contain combinations of canyon, apron, 

fan, and axial-channel turbidite-system elements. 

Ancient analogs such as the North China and North Sea 

rift basins appear to contain similar complex patterns of 

aprons, fans, and channels; these basins also show that 

the turbidite systems may change from one type to 

another at the same location as the basin setting evolves 

through geologic time. Development of excellent turbidite reservoir beds in these ancient basins indicates the 

value of defining modern turbidite systems as a guide for 

exploration and secondary recovery of petroleum in 

complex ancient turbidite systems. 

Domed, Rainfall-Dominated Peat 

Deposits in Indonesia as a Model for 

Low-Sulfur Coal 

Sandra G. Neuzil 

Aproximately 270,000 km2 of peat are present on 

the coastal lowlands of Indonesia and Malaysia. Most of 

the peat is domed (raised), rainfall dominated (ombrogenous), and thick (1-15 m), and most also overlies 

57 

marine sediments. Preliminary data from the analysis of 

peat samples collected at 16 sites distributed over three 

of these peat deposits in Riau and West Kalimantan 

Provinces, Indonesia, suggest that these peats are 

excellent analogs for some low-sulfur coal deposits in the 

Appalachian basin as well as others worldwide. 

Overall, the peat has a low ash content (93 samples 

average 2.5 percent ash) and a low sulfur content (71 

samples average 0.16 percent sulfur). Ash and sulfur 

contents are lower in peat that is more than 1 km from 

the deposit margin, more than 1 m below the peat surface 

(below the living root mat and fluctuating water table), 

and more than 1 m above the base of the peat (37 

samples, average 0.80 percent ash; 30 samples, average 

0.12 percent sulfur). Ash and sulfur contents are higher 

in the basal1 m of the peat deposit (17 samples, average 

8.5 percent ash; 13 samples, average 0.28 percent sulfur). 

At each sample site the pH is higher near the base of the 

peat, increasing from an average of 3.9 (pH range 

3.0-6.0) in the main peat body to an average of 4.9 (pH 

range 3.2-6.4) < 1 m above the base of the peat. 

Microbial activity and sulfur reduction and fixation may 

be more intense in these more neutral conditions at the 

base of the peat. 

The base of the peat deposits is generally less than 

a few meters above mean sea level and rarely below sea 

level. The peat appears to be hydrologically isolated from 

marine water based on the concentrations of total 

dissolved cations in peat pore water(1-260 ppm). The 

maximum of these values is less than 2 percent of their 

total concentration in sea water. Also, incursion of highsulfate sea water (2, 700 mg!L) into the peat would be 

expected to result in high-sulfur peat. Comparing peat 

samples from locations in close proximity to sea water to 

peat samples from other locations farther inland, sulfur 

contents are similar (16 samples < 10 km from sea water, 

average 0.12 percent sulfur; 18 inland samples > 10 km 

from sea water, average 0.13 percent sulfur), surface and 

basal peats are not included. 

Organic sulfur is the dominant form in a suite of 34 

samples from the three peat deposits (table 1, p. 59). As 

total sulfur increases, the organic sulfur fraction 

increases slightly. Note that all samples are low in total 

sulfur ( < 1 percent) and only two basal peat samples 

(<1m above the peat substrate contact) are represented 

in this sample set for forms of sulfur. 

During coalification, the content and form of sulfur 

may change, for example, by introduction of sulfur in 

ground water or by continued microbial reduction of 

sulfate. However, the major portion of each coal bed 

formed from tropical domed ombrogenous peat deposits 

such as these would be expected to have a low sulfur 

content even where the coal is overlying marine ' . sediments. Exploration for low-sulfur coal depostts 

should take into consideration an interpretation of the 
Table 1 (Nelson). Elements of modern siliciclastic multi-event turbidite systems in base-of-slope and basin floor settings 

[Modified from Nelson and Maldonado, 1988; Nelson and others, in press] 

Endmember 

"Sand-rich" 

fan 

"Mud-rich" 

fan 

"Sand-rich" 

apron 

"Mud-rich" 

apron 

Channel 

levee 

complex 

Axial 

channel 

Slope 

canyon 

Deep-sea 

channel 

Source 

type 

Morphologic 

characteristics 

Facies development 

proximal- distal 

Channelized depositional bodies 

Small point-source of a local Typically small (<100 km) 

river or littoral drift cell. radial fan with leveed 

channels and mid-fan 

sand lobes or suprafans. 

Large point-source of a 

single major mud-rich 

river or deep-sea channel. 

Typically large (> 100 km) 

elongate fan with extensive 

leveed channels and lower 

fan sand lobes or sheets. 

Upper fan: channel-levee 

deposits. 

Mid fan: sand lobes or suprafans. 

Lower fan: fringe turbidites. 

Basin plain: thin-bedded 

turbidite sheets. 

Upper fan: channel-levee 

deposits. 

Mid fan: bifurcated channellevee deposits. 

Lower fan: sand lobes. 

Abyssal plain: sand lobes to 

thin-bedded turbidite sheets. 

Non-channelized depositional bodies 

Line source of multiple 

debris chutes, typically in 

tectonically active basins 

(trench floor, pull apart, 

rift, caldera). 

Line source of multiple 

failures, typically on 

gullied slopes of muddy 

delta fronts and mature 

passive margins. 

Lobate delta? 

Drain canyons fans and 

aprons on trench or rift 

basin floor. 

Slope mass-wasting or river. 

Multiple canyons and (or) 

connecting channels. 

Typically small (few km) 

unchannelized slope base 

radial cone or coalesced 

cones that taper to a flat 

basin plain. 

Typically large (tens of km) 

unchannelized, elongate, 

slope base sediment tongue 

or tongues of irregular 

thickness, shape, hummocky 

surface and abrupt 

termination. 

Slope: chaotic sand and 

gravel in valley floors. 

Apron: wedges of sand and 

gravel sheets. 

Basin plain: thin-bedded turbidites. 

Slope: mounds of organized 

slide blocks and slumps of 

mud. 

Apron: slide debris lobes of 

chaotic mud and sand. 

Connecting channels 

Linear depositional channel 

without significant distal 

sand lobes. 

Conduits 

Erosional and (or) depositional slope valleys that 

connect downstream to 

fans, aprons, or deep-sea 

channels. 

Tectonically controlled basin 

floor erosional channels 

that connect downstream 

to fans or abyssal plains. 

58 

Channel floor: coarse-grained 

sediment-gravity-flow 

deposits. 

Levees: sand-rich thin-bedded 

overbank turbidites. 

Walls: with outcropping beds, 

mass movement or overbank deposits. 

Floors: erosional or with 

aprons and channel-levee 

deposits. 

Walls: with outcropping beds, 

mass-movement or overbank deposits. 

Floors: erosional or with 

channel-levee deposits. 

Examples 

California continental 

borderland basin fans 

(Dume, Hueneme, Magu, 

Navy, Redondo). 

Amazon, Astoria, Indus, 

Mississippi fans. 

Chile trench floor; Crater Lake 

caldera floor, African rift 

lake basins. 

Amazon, Ebro and Mississippi 

turbidite systems. 

Ebro channels; 

Chile trench floor and 

African rift lake floor axial 

channels. 

Astoria, Oropesa, Peiiiscola 

Redondo. 

Bounty Channel, Cascadia 

Channel, Valencia Valley. 
Table 1 (Neuzil). Forms of sulfur in a 34-sample suite from three 

Indonesian peat deposits 

Complete Low sulfur High sulfur 

sample set <0.2 percent ~ 0.2 percent 

Number of samples ---------- 34 26 8 

Average total sulfur 0.19 0.13 0.36 

(percent dry peat) 

Organic sulfur 82.7 80.9 88.7 

(percent of total sulfur) 

Pyritic sulfur 

(percent of total sulfur) 

Sulfate sulfur 

(percent of total sulfur) 

type of precursor peat deposit based on paleoclimate and 

paleotopographic reconstructions. 

Early Stage Diagenesis of 

Plant Biomolecules in Peats 

William H. Orem and Harry E. Lerch 

In the transformation of plant biomolecules to 

fossil fuels, many of the most pronounced chemical 

structural changes occur during the early stages of 

diagenesis. In the case of coal, early-stage diagenetic 

alteration of plant biomolecules occurs in peatlands 

where organic matter may accumulate due to the high 

productivity of algae and vascular plants and the 

stagnant, water-logged conditions, which inhibit biooxidation of the deposited plant remains. Few detailed 

studies on early diagenesis of the organic matter in peats 

have been conducted. We present herein the results of 

organic geochemical studies of peat cores that represent 

a number of different wetland environments. Several 

different analytical approaches (such as 13C nuclear 

magnetic resonance spectroscopy, analytical pyrolysis, 

and gas chromatography/mass spectroscopy) were 

utilized to examine changes occurring in the solid-phase 

organic matter in the peat and to study the chemical 

structures of extractable organic compounds in the peat 

and dissolved organic matter (DOM) in the associated 

pore water. 

In figure 1 (p. 60), solid-state 13C nuclear magnetic 

resonance (NMR) spectra of peats from two very 

different wetlands (the Everglades, Florida, and 

Okefenokee Swamp, Georgia) are shown. In the core 

from a sawgrass area in the Everglades, the major change 

in the organic matter with depth is the loss of labile 

carbohydrates (primarily cellulose) by biodegradation. 

This change is shown in the 13C NMR spectra of the 

whole peat as a gradual decrease in the intensity of the 

peak at 72 ppm. Aliphatic organic matter (broad peak in 

0-50 ppm region ofNMR) and lignin from vascular plant 

8.9 

8.4 

59 

10.1 5.0 

9.1 6.4 

remains (peaks at 56 ppm, 110-150 ppm, and 150-160 

ppm) are selectively preserved in this peat core. 

Analytical pyrolysis and gas chromatography/mass 

spectroscopy have shown that these aliphatic residues 

may originate from vascular plant waxes. 

In contrast, the 13C NMR spectra of whole peats 

from a core taken in Okefenokee Swamp show that the 

organic matter is much more biodegraded than that from 

the Everglades. The Okefenokee peats show a rapid loss 

of carbohydrates and vascular plant lignin with increasing 

depth, leaving only refractory aliphatic substances 

preserved. Note the near total absence of peaks for lignin 

at 56 ppm, 110-150 ppm, and 150-160 ppm in the 13C 

NMR spectra at the bottom of this core (fig. 1 ). The 

biodegradation of lignin and carbohydrates distinctly 

differentiates the Okefenokee peats from those in the 

sawgrass area of the Everglades. 

Geochemical studies of the dissolved organic 

matter (DOM) in peat pore waters may also provide 

information on the biodegradation of plant biomolecules 

in peats. The DOM is an intermediate in the degradation 

of organic matter from macromolecular biopolymers in 

the peat to mineralized organic matter in the form of 

C02 and (or) CJL. 13C NMR analysis of DOM from 

neutral pH peatlands such as the sawgrass area of the 

Everglades shows that the chemical structure of the 

DOM is dominated by carbohydrates. The dominance of 

carbohydrates in the DOM is consistent with the 

dominant degradative process occurring in the solid peat: 

the loss of carbohydrates, as mentioned previously. In 

contrast to the situation in neutral-pH peatlands, the 

chemical structure of DOM from acidic "blackwater" 

peatlands such as the Okefenokee Swamp is dominated 

by aliphatic and aromatic moities, with little or no 

carbohydrate content (

13C NMR analysis). Analytical 

pyrolysis and gas chomatography indicate that the 

aromatic structures in the DOM may be derived from the 

biodegradation of lignin, which is consistent with the 

nature of organic matter diagenesis observed in the 

whole peat (fig. 1 ). Other acidic, "blackwater" peatlands 

such as Dismal Swamp, Virginia, and several Indonesian 
~ 

Everglades, FL Okefenokee Swamp, GA 

0 - 5 em 0 - 5 em 

10 - 25 em 10 - 15 em 

25 - 40 em 

40 - 55 em 

70 - 90 em 

60 - 80 em 

I I I I I I I I I I I I I I I I 

250 200 150 100 50 0 -50 -100 250 200 150 100 50 0 -50 -100 

ppm ppm 

Figure 1 (Orem). 13C NMR spectra of whole peats from two cores representing different peat-forming wetlands: the sawgrass peat area of the Everglades, Florida, 

and water-lily prairie area of the Okefenokee Swamp, Georgia. The NMR scale is in units of ppm relative to tetramethylsilane. 
swamps also exhibit high degrees of lignin 

biodegradation in the peat and highly aromatic DOMin 

the pore water. This aromatic-rich DOM may play a 

significant role in imparting a low pH and dark, tea-color 

to the "blackwater" which is characteristic of these 

wetlands. Only aliphatic residues are preserved in these 

acidic peats, which may represent modern analogs of 

ancient coal-forming peatlands that produced aliphaticrich coals, for example, the brown coals of southeastern 

Australia. The deposits of acidic peatlands may also 

represent environments responsible for oil-forming 

coals. 

New Tonstein Beds in the Middle 

Pennsylvanian of the Central Appalachian 

Basin-Time Lines for Basin Analysis 

W.F. Outerbridge, P.C. Lyons, and 

D.M. Triplehorn 

Tonsteins, which are altered volcanic ash, mark 

instantaneous events over large areas and thus are 

excellent time markers for basin analysis. In the Middle 

Pennsylvanian of the central Appalachian basin, they are 

gray claystones, usually from 1 to 5 in. thick, and 

probably of an original rhyodacitic composition. 

We can demonstrate six new tonstein beds-a flint 

clay bed from the Olive Hill Clay Bed of the Breathitt 

Formation, flint clay beds in the Upper Banner, Williamson, and Little Fire Clay coal beds, a flint clay from the 

Hitchens clay, and the flint clay beds associated with the 

Princess No. 6 coal bed-in stratigraphic order from 

oldest to youngest. They span most of the Middle 

Pennsylvanian (Westphalian A-D) in the central 

Appalachian basin. 

These tonsteins are identified by the ubiquitous 

presence of quartz as clear monocrystalline flakes, thin 

blades, and euhedral a-quartz crystals pseudomorphic 

after ,8-quartz; high-temperature potassium feldspar 

(sanidine?); and euhedral, commonly acicular zircons. 

Aluminum phosphate minerals of the crandallite group, 

euhedral platy crystals of rutile(?), and grains of anatase 

perhaps derived from titaniferous magnetite are also 

common. The matrix is a mixture of microcrystalline 

kaolinite, quartz, and, commonly, some illite. 

Some of the tonstein beds have been traced from 

West Virginia into Kentucky and Ohio, but more detailed 

thickness, mineralogical, trace-element, and geochronological data are needed to identify source areas, synchroneity with acidic plutons, and absolute age dates. 

However, that a source area lies in the eastern Piedmont 

is a reasonable hypothesis, based on isopachous data for 

the Fire Clay coal-bed tonstein and the published age 

( :::::311 Ma) that is coeval with some Piedmont granites. 

61 

40 Ar/ 9 Ar dating of potassium feldspar, now in progress, 

will allow estimation of Middle Pennsylvanian 

sedimentation rates, correlations with acidic plutons, and 

intercontinental correlations. 

Petroleum Potential of Midcontinent Rift 

System, Iowa-Organic Matter and 

Porosity Preserved in 1-Billion-Year-Oid 

Rocks 

James G. Palacas, James W. Schmoker, and 

Raymond R. Anderson 

Preliminary hydrocarbon source rock and reservoir 

evaluations have been made of the thickest section 

(14,100 ft; 4,298 m) of Middle Proterozoic sedimentary 

rocks sampled anywhere along the trend of the Midcontinent Rift System. Source rock and porosity assessments 

are based on analyses of core and drill cutting samples, 

and electric logs from the 17,851-ft (5,441-m) deep 

AMOCO M.G. Eischeid #1 well, which was drilled in 

1987 in the Defiance basin northwest of the medial Iowa 

horst near the town of Halbur, Carroll County, westcentral Iowa. A 7,200-ft (2,195-m) thick basal sequence 

of Precambrian clastic rocks encountered in the Eischeid 

well has lithologies similar to those of the Oronto Group 

of Wisconsin, and an overlying 6,900-ft (2,103-m) thick 

Precambrian clastic sequence resembles the rocks of the 

Bayfield Group in Wisconsin. The Oronto and Bayfield 

Groups are part of the Keweenawan Supergroup. 

In the Eischeid #1 well, the fine-grained 

predominantly red rocks in the interval equivalent to the 

Bayfield Group contain minimal organic matter: total 

organic carbon (TOC) content is less than 0.10 percent, 

indicating no petroleum source-rock potential. The very 

low TOC content is attributed largely to oxidizing 

depositional environments. 

The petroleum source potential of a large portion 

of the underlying rocks, equivalent to the Oronto Group, 

is also generally quite poor: TOC is commonly less than 

0.10 percent and Rock-Eval genetic potential (S1 + Sz) 

less than 0.10 mg HC/g rock. However, between depths 

of about 15,000 and 16,425 ft (4,570-5,005 m), mediumto dark-gray, pyrite-bearing, laminated shales (mudstones) are common. In these shales (mudstones), which 

are possibly equivalent to the Nonesuch Shale of 

Wisconsin and Michigan, TOC contents reach 0.1-1.4 

percent, and average about 0.6 percent; genetic 

potentials range from 0.1 to 0.4 mg HC/g rock, hydrogen 

indices from 20 to 80 mg HC/g TOC, and chloroformextractable bitumen contents from 10 to 60 ppm. 

Based on Rock-Eval Tmax, vitrinite-like 

reflectance, thermal alteration index (TAl), ratios of 

extractable hydrocarbons to TOC, and Lopatin 

modeling, the shales deeper than 15,000 ft ( 4,570 m) are 
ranked as overmature with respect to oil generation. 

More precisely, the maturity of the shales is at least in the 

wet-gas zone of hydrocarbon generation and possibly 

extends into the dry-gas zone. Accordingly, although at 

present these shales have little remaining capacity to 

generate additional hydrocarbons, in the geologic past 

they could have generated significant amounts of 

hydrocarbons. We speculate that equivalent shale facies 

might have better source rock potential if present at 

shallower depths, under lower levels of thermal maturity, 

along the basin flanks away from the frontal fault zone of 

the medial horst. 

Sandstone constitutes 1,721 net ft (525 m), or 29 

percent of the interval between 11,450 and 17,340 ft 

(3,490 to 5,285 m) of the rocks equivalent to the Oronto 

Group in the Eischeid well. Sandstone is distinguished 

from the siltstone and shale that make up the remainder 

of the interval by differences in the photoelectricabsorption, density-porosity, and neutron-porosity log 

traces and (secondarily) by the lithologic descriptions 

prepared from drill cuttings. 

Sandstone porosity below 11,450 ft (3,490 m), as 

determined from compensated density and neutron logs, 

ranges between 1 and 6 percent and averages only 2.3 

percent. "Better" porosities of 3.5 percent or more are 

distributed throughout the interval studied and do not 

correlate with either (1) depth, (2) the zone of more 

reducing environment (the zone of dark-gray, pyritic, 

laminated shales), or (3) the reported presence of 

bitumen- or pyrobitumen-like "intergranular black 

residue." However, Th:K ratios derived from the spectral 

gamma-ray log suggest that intervals of better sandstone 

porosity may have a higher percentage of plagioclase 

feldspar. It is thus possible, but certainly not proven, that 

enhanced sandstone porosity in the Eischeid well may be 

diagenetically linked to plagioclase feldspar. We 

speculate that the porosity of equivalent sandstones may 

be higher on the basin flanks because of shallower burial 

and resulting lower levels of time-temperature exposure. 

Preliminary Reinterpretation of the 

Ouachita Frontal Zone Near Hartshorne, 

Oklahoma, Based Chiefly on Seismic 

Reflection Data 

W.J. Perry, Jr., Warren Agena, and 

N.H. Suneson 

A north-south seismic reflection profile across the 

frontal zone of the Ouachita thrust belt in the Hart62 

shorne, Oklahoma, region illustrates the triangle-zone 

style of deformation: a wedge-shaped structure, floored 

by a foreland-directed decollement, at the foreland tip of 

which a complementary hinterland-directed thrust of 

equal and opposing slip occurs shallower in the section, 

dipping toward the foreland. These opposing thrusts 

form the front of the triangle zone. In our interpretation, 

the Choctaw thrust is simply the frontal imbricate along 

the southern margin of this complex, partially eroded 

triangle zone. This triangle zone and associated 

imbricates appear to represent about 6 miles (10 km) of 

shortening. The Middle Pennsylvanian Hartshorne 

Sandstone appears to be merely peeled upward along the 

northern margin of this triangle zone and not significantly 

displaced with respect to the Arkoma basin to the north. 

The Middle Pennsylvanian Atoka Formation, 

which underlies the Hartshorne Sandstone, is interpreted 

to form the roof of a deeper imbricate zone near the 

northern end of the profile. This zone is interpreted to be 

a duplex fault zone, that is, an imbricate zone bounded by 

floor and roof thrusts which structurally isolate the zone 

from the overlying roof and underlying floor sequences. 

The duplex interpreted on the seismic profile near Hartshorne is unusual because it contains two forelanddipping backthrusts between the floor and roof thrusts. 

The floor thrust of this deeper zone appears to be a 

decollement for a distance of more than 7 miles (11 km) 

north-south within the Upper Devonian and Lower 

Mississippian Woodford Shale and Upper Mississippian 

Caney Shale. Beneath the floor thrust of this deeper 

imbricate zone, the Arbuckle through Hunton Groups 

(Cambrian to Devonian) are cut by steeply dipping 

extension faults, in which the sense of displacement 

appears generally down to the south. The floor thrust 

appears to rise more steeply to the north where it crosses 

each of the extension faults, suggesting that minor ramps 

in the floor thrust were sited by underlying structures. 

The extension-fault-bounded blocks beneath the floor 

thrust may illustrate the style of structural traps involved 

in the subthrust Arbuckle gas play near Wilburton. 

In summary, typical triangle zone features, 

suspected by earlier workers, including J.K. Arbenz, are 

imaged by a high-quality seismic reflection profile across 

the frontal zone of the Ouachita thrust belt near Hartshorne, Oklahoma. Down-to-south extension preceded 

thrusting. Frontal thrusting is younger than the McAlester Formation of late Middle Pennsylvanian (Desmoinesian) age, the youngest Paleozoic stratigraphic unit 

preserved along the seismic profile. 
Architectural Studies in Eolian Reservoir 

Rocks-The Lower Jurassic Nugget 

Sandstone of Northeastern Utah 

Fred Peterson and C.J. Schenk 

Lower Jurassic eolianites in the Western Interior 

of the United States include deposits of the largest erg 

(eolian sand sea) that ever existed in North America and 

perhaps in the world. Previous workers in northeastern 

Utah have applied several names to these rocks, 

including Glen Canyon, Navajo, and Nugget Sandstone. 

However, we prefer the term Nugget (a) because the 

beds closely resemble the type Nugget nearby in 

Wyoming, (b) because the strata correlate with the entire 

Glen Canyon Group farther south rather than just the 

Navajo Sandstone part of it, and (c) because Glen 

Canyon Sandstone is a junior synonym for the Nugget in 

this area. The Nugget is an excellent but anisotropic 

reservoir rock that produces hydrocarbons from about a 

dozen medium-sized oil fields in the southern part of the 

overthrust belt of southwestern Wyoming and northern 

Utah. There, it has been faulted against or near good 

source beds that were buried to sufficient depths to 

generate hydrocarbons. 

Our study has concentrated on lateral and vertical 

variations in eolian dune, sand-sheet, and sabkha 

deposits that may influence fluid movement and sweep in 

reservoir sandstone beds of the Nugget. Because 

exposures tend to be poor and of limited areal extent in 

the Wyoming-Utah overthrust belt, most of the research 

was done near Vernal, northeastern Utah, where fairly 

continuous exposures are amenable to architectural 

studies. The Nugget in that area consists of a stacked 

sequence of eolian dune, sand-sheet, and clastic sabkha 

deposits with rare thin and areally limited lacustrine 

limestone beds. 

Eolian dune sandstone beds range from simple to 

complex, the complex being more abundant. A simple 

dune deposit consists almost entirely of high-angle 

avalanche cross-strata that grade downward into windripple and grain-fall apron strata. Of such deposits, most 

occur in a single tabular-planar or wedge-planar set that 

can be traced for hundreds of meters on outcrops 

oriented parallel to wind flow, which was roughly from 

north to south. Over this distance, set thicknesses range 

from several to 10 or more meters. Simple trough-shaped 

sets are also present, but not as abundant as the planar 

sets. 

Complex dune deposits range from a coset of 

eolian dune cross-strata that resembles a simple set but 

has multiple downwind- or southward-dipping internal 

bounding surfaces, to compound cosets with nested 

large-scale trough-shaped sets, to thick sets (15 m or 

63 

greater) that commonly grade downwind into several 

thinner sets. Some of the complex eolian dune deposits 

exhibit significant internal variation, including several 

orders of bounding surfaces, and a complex intercalation 

of avalanche and wind-ripple strata. 

The best original porosity and permeability in these 

beds would be in the avalanche cross-strata, but at least 

moderate porosity and permeability can be expected in 

the wind-ripple and grain-fall apron laminae. Fluid flow 

should be more complicated in the complex eolian dune 

deposits than in the simple dune deposits, not only 

because of the multiple bounding surfaces, but also 

because of the complex distribution and orientation of 

the cross-strata and apron deposits. For both the simple 

and complex types of dune deposits, the individual eolian 

sets or cosets cannot be expected to extend across the 

areal extent of typical Nugget oil fields (roughly 3-10 km 

in width). 

Some of the major bounding surfaces are marked 

by slight erosional irregularities 2-6 em high that are 

mostly in the finer grained (very fine to fine-grained) 

cross laminae of the underlying set. In vertical exposures, 

these surfaces tend to be parallel to sabkha units higher 

or lower in the formation, or else thin sabkha units locally 

wedge in along some of these surfaces. These major 

bounding surfaces with slight erosional irregularities may 

be Stokes' surfaces that formed where eolian erosion in 

front of an advancing dune occurred down to the water 

table or at least down to the zone of capillary action just 

above the water table. Early cementation then took place 

by evaporative concentration of solutes in the ground 

water, especially in the finer grained laminae where 

capillary action is greatest. Thus, some of the major 

bounding surfaces, especially those associated with 

shallow water tables, may lie on slightly better cemented 

zones in the upper parts of underlying sets or cosets. 

Recent studies of major bounding surfaces ("super 

surfaces") in other eolian formations suggest that these 

zones may have considerable lateral extent, could easily 

extend across an entire oil field, and therefore could be 

slight but important barriers to vertical fluid movement. 

Eolian sand-sheet deposits consist largely of 

laminae produced by the migration of wind ripples, but 

they also include intercalated structureless laminae that 

may be grain-fall or poorly defined wind-ripple deposits. 

Porosity and permeability are excellent although not as 

high as in the crossbedded dune facies. Nugget sandsheet deposits are most abundant in Idaho and westernmost Wyoming; they are much less common farther 

south and southeast, including the Vernal study area. 

Clastic sabkha sandstone beds generally contain 

irregular or wavy-bedded laminae with a moderate 
amount of lateral variation produced by thin remnants of 

eolian foreset cross-strata 1-20 em thick, contorted 

strata, and wind-ripple laminae. Individual sabkha units 

characteristically range in thickness from less than a 

meter to several meters across a distance of several 

hundred meters. Sabkha deposits are especially abundant 

in the basal approximately 30 m of the Nugget where they 

form a continuous zone that can be traced throughout 

northern Utah, westernmost Wyoming, and central Utah. 

Higher in the Nugget, sabkha units form discontinuous 

lensoid bodies on the order of 1 to several kilometers in 

areal extent. Sabkha units typically are better cemented 

and more poorly sorted than dune and sand-sheet 

deposits, properties that make them significant barriers 

to fluid migration. However, fracture porosity in areas of 

intense structural deformation, such as in the overthrust 

belt, may improve their transmissivity. Similarly, the rare 

lacustrine limestone beds should impede fluid flow but 

also may be expected to be fractured in structurally 

complex areas. Because of their generally limited areal 

extent, sabkha units in the upper part of the formation 

would not be expected to extend completely across a 

typical Nugget oil field; however, their presence could 

well make field development difficult. 

In summary, although the Nugget Sandstone can 

be an excellent reservoir medium, it contains numerous 

sedimentologic heterogeneities that make optimum field 

development a challenge. Vertical fluid migration may be 

expected to be hindered in various degrees by apron and 

persistent sand-sheet deposits, by slightly greater 

cementation beneath some of the major bounding 

surfaces (especially Stokes' surfaces), by sabkha deposits, 

and by lacustrine limestones. Lateral fluid migration 

should be optimal in the crossbedded dune facies, 

especially perpendicular to paleowind flow along crossbed laminae. However, lateral discontinuities produced 

by inclined or curved bounding surfaces overlain by 

apron deposits may impede lateral fluid movement. 

Algal Mound Carbonate Reservoir, Aneth 

Oil Field, Paradox Basin, Utah-Origin 

and Related Petroleum Geology 

James A. Peterson 

The Aneth oil field (approximately 400 million 

barrels ultimate recovery) contains three-fourths of the 

oil reserves discovered in Pennsylvanian reservoirs of the 

Paradox basin. The field occurs within an isolated 

northwest -trending Desmoinesian (Pennsylvanian) algal 

carbonate bank buildup located about 25 mi {40 km) 

basinward of the main carbonate shelf of the basin in 

Utah. Desmoinesian deposition was strongly cyclic, with 

64 

as many as 30 main evaporite-carbonate cycles 

recognized. The Aneth algal bank is part of the Desert 

Creek cycle, which is the first cycle above that of the most 

widespread salt-bearing cycle. The Desert Creek 

carbonate facies grades basinward to increasingly 

prevalent evaporite facies, dominated by thick salt beds 

in the basin center. Within the isolated algal-mound 

facies, the Desert Creek cycle is characterized by a 

vertical succession that includes: (1) basal black, organicrich, dolomitic, silty shale, and {2) overlying dark chalky, 

finely crystalline dolomite, which grades upward into {3) 

the main carbonate mound facies, dominated by 

accumulations of calcareous, leafy green algae with 

associated brachiopods, fusulinids, small foraminifera, 

ostracodes, and rarely, corals. Mound buildups are 

overlain by a relatively thin, black, organic-rich shale 

unit, the basal bed of the succeeding mound-bearing 

Ismay cycle. This upper shale unit thickens markedly on 

the flanks of the Desert Creek and other mounds. 

The basal black shale unit is thickest beneath the 

Aneth mound facies and also is commonly thicker 

beneath many other Desert Creek and Ismay algalmound buildups. Detailed regional studies suggest that 

the Aneth algal facies was deposited on a broad 

southeast-trending organic-rich mud and silt bank. This 

bank provided submarine topographic relief which 

localized the Aneth algal-mound complex. These 

interrelated carbonate and clastic depositional processes 

resulted in the close association between source rock, 

large reservoir, and seal at Aneth and contributed 

significantly toward the large size of the Aneth 

accumulation. Broader scale factors involved in 

development of the Aneth and other Paradox basin 

carbonate mounds include: (1) global paleolatitudinal 

position of the Paradox basin; (2) paleogeographicpaleotectonic framework ofthe basin region; (3) climatic, 

prevailing-wind, and ocean-current patterns, strongly 

influenced by the above factors; ( 4) eustatic changes in 

sea level; and (5) position of the Aneth mudbank-mound 

area with respect to the Paradox basin marine accessway. 

Pyritic Sulfur and Trace-Element 

Affinities in Facies of the Upper Freeport 

Coal Bed, Allegheny Formation, 

West-Central Pennsylvania 

Brenda S. Pierce and Ronald W. Stanton 

The distribution of pyritic sulfur and associated 

trace elements indicates two sources of trace-element 
enrichment in facies of the Upper Freeport coal bed. 

Samples were collected from 62 localities in a 120 mi2 

area of west -central Pennsylvania. A generalized stratigraphic section of the Upper Freeport coal bed (fig. 1, p. 

66) shows the coal-bed facies (A to E), upper parting 

(UP), and lower parting (LP). The coal-bed facies, which 

represent developmental stages during peat formation, 

differ compositionally and are continuous and mappable 

over the study area. 

The Upper Freeport coal bed began forming as a 

low-lying, topogenous peat (facies E and D) that was 

susceptible to sediment influx. The peat body became 

slightly raised (facies C and C'), which restricted clastic 

input to the margins of the swamp. In the western part of 

the study area, peat accumulation ended when 

freshwater lakes formed and the dark laminated shales 

that now overlie the coal bed were deposited. These 

shales are represented by the upper parting (UP) in the 

eastern part of the study area, where peat accumulation 

resumed (B) as peat islands on the emergent, slightly 

raised areas underlain by facies C. Facies A' (nonbanded 

coal) was formed by mixing at the edges of the peat 

island, and facies A (also nonbanded) was formed by the 

gradual inundation of the peat by shallow lakes. 

The distribution and stratigraphic concentrations 

of total sulfur content, sulfur forms, and trace elements 

related to sulfur-As, Se, Hg, Ph, Zn, and Cd-were 

examined and correlated by facies. Mean values of these 

elements, plotted by facies, show that the highest 

concentrations are at the top and bottom of the coal bed. 

The lowest concentrations of these elements are most 

commonly in facies that constitute the middle of the coal 

bed. Elemental compositional means for the middle and 

the top facies, respectively, are as follows: As, 10.6 and 

59.8 ppm; Se, 1.7 and 10 ppm; Pb, 4.76 and 25.8 ppm; and 

Zn, 8.8 and > 61 ppm. The mean pyritic sulfur content 

varies from 0.8 to 2.6 percent in the various facies. The 

amount of organic sulfur in the Upper Freeport coal bed 

is relatively lower (0.5-1.3 percent) and much less 

variable than pyritic sulfur. Pyritic sulfur is responsible 

for variations in total sulfur and trace-element 

characteristics. 

Correlation coefficients indicate that pyritic sulfur 

and As have a strong positive correlation in most facies 

data sets. Detailed geochemical cross sections show that 

As commonly follows the same trends as pyritic sulfur 

throughout the coal bed, both laterally and vertically (fig. 

1). The pyritic sulfur and As values in the middle facies 

are very low throughout most of the coal bed. In the 

interior and eastern parts of the study area (represented 

by locations 3 and 4, fig. 1 ), pyritic sulfur and As values 

are highest at the top and bottom of the coal bed, perhaps 

indicating a relationship to associated strata. In the 

western part of the study area (locations 1 and 2, fig. 1 ), 

the highest pyritic sulfur and As values are found in the 

65 

top and bottom of the coal bed in only half of the 

locations studied; in the other half, highest values were 

found in facies C. 

In the top and bottom facies, the following 

statistically significant correlations exist: As-Se, As-Hg, 

Pb-Se, Pb-Cd, and As-Pb. These correlations may 

indicate diagenetic influence from associated strata. 

However, these elemental correlations are not significant 

in facies C', which is the uppermost facies in the western 

part of the study area. Therefore, either the epigenetic 

processes operative in the central and eastern part of the 

study area were not significant in the western part, or 

these correlations may indicate some degree of syngenetic relationship with the original peat facies. 

Alternatively, certain elements correlate only 

within the middle facies of the bed: Zn-Cd, Cd-pyritic 

sulfur, Hg-pyritic sulfur, and Zn-Se. These correlations 

appear to have been related to conditions present during 

peat formation. The mode of occurrence of these 

elements is not yet known; however, sphalerite has not 

been detected from microscopic analyses or LT A 

mineralogy. 

Although pyrite is inferred to contain As, Zn, Cd, 

Pb, and Se, there appear to be at least two suites of 

associations within the Upper Freeport coal bed: HgCd-Zn-As, possibly a syngenetic phase found in the 

middle facies, and Se-Pb-As-Hg, possibly an epigenetic 

phase, associated with the top and bottom of the coal 

bed. These two suites imply a paragenesis of pyrite 

formation that first concentrated Hg, Cd, Zn, and As, 

and later Se, Pb, As, and Hg. 

Interplay of Tectonism and Sea-Level 

Change-Lessons from the 

U.S. Atlantic Margin 

C. Wylie Poag 

Isopach maps (scale 1:1,000,000) of 23 successive 

stratigraphic sequences demonstrate that marine depocenters on the United States middle Atlantic margin have 

migrated significant distances during their 190-millionyear postrift history (Early Jurassic to present). These 

depocenters migrated in two principal ways: (1) 

latitudinal shifts from north to south (and vice versa) and 

(2) bathymetric shifts from continental shelf to 

continental slope or rise (and vice versa). The major 

latitudinal migrations were caused by changing rates of 

differential uplift among the three principal highland 

source terrains (central Appalachians, Adirondacks, and 

New England Appalachians) that supplied the offshore 

basins with terrigenous detritus. The historical pattern of 
en 

en 

• 1 

en 

Cl) 

J: 

() 

c 

0 

,... 

I 

• 

2 

C' 

c 

.0 

LP 

E 

Localities 1 

West 

Nj 4 

p 

~ 

3 

• 

A 

~0 

• 

.· ,~ .. , .. ' .. 

)t 

PA 

___ .,__ ________ __J 

2 

p A 

w~o 

3 4 

East 

Figure 1 (Pierce). Element distributions in facies of the Upper Freeport coal bed. Four locations selected from 62 vertical sections examined throughout study area. P, pyritic sulfur values in percent; A, arsenic values in ppm. 
latitudinal depocenter migration shows that the main 

source for terrigenous detritus during most of the postrift 

history of the offshore basins was the central 

Appalachian terrain. During the Late Cretaceous, 

however, the main terrigenous source was the New 

England Appalachians. The Adirondack terrain 

contributed less sediment than the other two principal 

terrains, but was an important source during the Jurassic 

and Early Cretaceous and throughout much of the Cenozoic. 

Some bathymetric migrations of depocenters 

appear to have been unrelated to differential uplift of the 

source terrains; these migrations were caused by eustatic 

changes. For example, a eustatic fall at the end of the 

Cretaceous restricted principal depocenters to the 

continental slope and rise, while exposing the shelf to 

extensive erosion. In contrast, high global sea levels 

during the Hauterivian, Cenomanian-Turonian, and 

much of the Paleogene allowed mid-shelf depocenters to 

develop at the expense of deep-water depocenters. 

Abrupt surges in sediment supply could overcome the 

effects of relatively high sea levels, however, to produce 

thick depocenters on the continental slope and rise. 

Examples of such sediment-supply overprints are 

particularly conspicuous on the Neogene and Quaternary 

isopach maps. 

Thick siliciclastic depocenters are attractive targets 

for petroleum exploration, but their migration through 

geologic time complicates the search for commercial 

reserves. A comparison of depocenter locations with the 

positions of exploratory wells in the middle Atlantic 

offshore region shows that few of the major depocenters 

have been adequately tested for hydrocarbons. 

Controls, Habitat, and Resource 

Potential of Ancient Bacterial Gas 

Dudley D. Rice 

More than 20 percent of the world's natural gas 

reserves are estimated to have been generated by the 

decomposition of organic matter by anaerobic bacteria at 

low temperatures. Such gas is referred to as bacterial gas. 

This estimate does not include the enormous resources 

of bacterial gas contained in gas hydrates in both 

permafrost and deep-sea settings. Further large 

resources of bacterial gases probably remain to be 

discovered in frontier areas or are already known to be 

present in subcommercial accumulations and in 

accumulations bypassed in past exploration efforts. 

The factors that favor significant generation and 

thus possible accumulation of bacterial methane are 

anoxic environment, low sulfate content, low 

67 

temperatures, abundant organic matter, and sufficient 

space for the bacteria to thrive. Rapid deposition is also 

critical for the preservation of organic matter prior to and 

during methane generation and the preservation of 

methane after its generation. The interrelation of these 

key factors indicates that most bacterial gas is probably 

generated at burial depths less than 1 km. 

Ancient bacterial gas can be distinguished by its 

chemical and isotopic composition. The hydrocarbon 

fraction of bacterial gases consists mainly of methane 

(Cz+ values are generally less than 1 percent). The minor 

amounts of heavier hydrocarbon gases result from early 

thermogenic or diagenetic processes. The most 

diagnostic feature of ancient bacterial gases is the 

isotopic composition of their methane component: o

13C 

values are generally lighter than -60 ppt and oD values 

are usually in the range of -150 to -250 ppt. This isotopic 

composition indicates that the methane resulted from 

C02 reduction, even though methane generation by 

fermentation is observed in recent sediments: methane 

derived by fermentation is depleted in deuterium in 

contrast to that generated by COz reduction. Bacterial 

methane generation by fermentation is probably 

restricted to very young, recently deposited sediments, 

and the methane is largely lost to the atmosphere. In 

contrast, methane production by C02 reduction can take 

place in relatively older, more deeply buried sediments 

deposited in both marine and nonmarine environments 

and thus is more likely to be trapped. 

Bacterial gas can be buried to much greater depths 

after generation ceases, where it is commonly mixed with 

varying amounts of thermogenic gas. Gases of mixed 

bacterial and thermogenic origin are characterized by 

o

13C1 values of -60 to -50 ppt and Cz+ values of as much 

as 5 percent. 

Significant accumulations of ancient bacterial gas 

have been discovered on five continents: Africa, Asia, 

Europe, North America, and South America. These 

accumulations are in Mississippian and younger rocks, 

occur at burial depths as much as 4,500 m, are commonly 

mixed with some thermogenic gas, and are associated 

with a variety of rock types (carbonate, clastic, and coal) 

and marine and nonmarine depositional settings. 

Genetic Lithofacies in the Dakota 

Sandstone, a Major Oil- and GasProducing Formation, Northern San Juan 

Basin, Colorado and New Mexico 

J.L. Ridgley 

The Cretaceous Dakota Sandstone in the northern 

San Juan Basin and vicinity, Colorado and New Mexico, 
consists of three major transgressive sequences overlying 

an entirely fluvial sequence. Each transgression 

coincided with a westward shift of the shoreline. The 

Dakota consists of, in ascending order, the Encinal 

Canyon Member, Oak Canyon Member, Cubero 

Tongue, Paguate Sandstone Tongue, and Twowells 

Sandstone Tongue. The Cubero and Paguate Tongues 

are separated by the Clay Mesa Tongue of the Mancos 

Shale, and the Paguate and Twowells Tongues are 

separated by the Whitewater Arroyo Shale Tongue of the 

Mancos Shale. An erosional unconformity of regional 

extent marks the base of the Dakota. The Encinal 

Canyon Member consists of fluvial sandstone and 

conglomerate that filled incised valleys cut during a 

sea-level fall; the deepest valleys occur in a more seaward 

direction. 

The Oak Canyon-Cubero, Clay Mesa-Paguate, and 

Whitewater Arroyo-Twowells intervals each comprise a 

single genetic package that coincides with a major 

depositional cycle; each cycle began with a marine 

transgression and ended with a regressive pulse. The Oak 

Canyon, Clay Mesa, and Whitewater Arroyo are 

marginal-marine and marine shale sequences. Deltaic 

and offshore marine sandstones, possibly remnants of 

barrier bars, characterize the Cubero and Paguate, which 

separate the marine shale members. The Twowells is 

entirely marine in this area. 

Westward from the area of entirely marine 

deposits, each genetic package changes facies to entirely 

fluvial deposits. These fluvial sequences are commonly 

lumped with the Encinal Canyon Member as part of the 

main body of the Dakota. The sandstone and shale 

distribution and geometry of the entirely fluvial sequence 

permit separation of individual genetic packages. For 

each genetic package, lower delta plain rocks 

characterized by distributary channel fill, coals, or bay fill 

are laterally adjacent to thick coastal or nearshore 

marine sandstones. Upstream, lower delta plain rocks 

are replaced by meander-channel sandstone and overbank mudstone of the lower alluvial plain. Also 

upstream, the meander-channel sandstone units are 

thicker and more extensive laterally. During each 

subsequent transgression and resulting shoreline shift, 

the fluvial depositional environments also shift. For 

example, as a result of the shoreline shift between 

Paguate and Cubero time, lower delta plain rocks overlie 

lower alluvial plain rocks. Coals of the lower delta plain 

are especially useful in identifying major shoreline shifts 

that are due to transgression. 

Oil and gas are produced from all sandstone facies 

in the Dakota, although marine sandstones are the 

primary exploration targets. Gas is the principal 

hydrocarbon produced in the deeper part of the northern 

San Juan Basin. Oil production or shows are confined to 

the Hogback monocline and Archuleta arch, which 

68 

bound the northern San Juan Basin on the west and east, 

respectively. Syndepositional uplift of the Hogback monocline and Four Corners platform to the west of the San 

Juan Basin resulted in both a thinner sequence of Dakota 

in these areas and reduced reservoir continuity. Laramide folding and faulting have segmented sandstones 

into semi-confined reservoirs, but, except locally, do not 

appear to have destroyed their capacity to contain gas. 

Basin Analysis Study of the San Juan 

Basin, Colorado and New Mexico 

J.L. Ridgley and A.C. Huffman, Jr. 

During 1985-1989, the U.S. Geological Survey 

conducted a basin analysis study of the San Juan Basin 

and vicinity under the Evolution of Sedimentary Basins 

Program. Major scientific problems addressed in the 

study were: (1) refining basin lithostratigraphy and biostratigraphy, (2) documenting periods of tectonism and 

relations of depositional sequences to tectonics, and (3) 

relating tectonic-sedimentary histories to development of 

energy and mineral resources. Final published results 

will include isopach and structure maps, regional cross 

sections, and numerous topical and synthesis reports 

documenting results of stratigraphic, sedimentologic, 

structural, and geochemical studies. 

The San Juan Basin is located in northwest New 

Mexico and southwest Colorado in the southeastern part 

of the Colorado Plateaus physiographic province. More 

than 14,000 ft of Paleozoic, Mesozoic, and Cenozoic 

continental and marine rocks fill the basin. Regional 

structural, stratigraphic, and sedimentologic studies have 

revealed a complex history of deposition, nondeposition, 

uplift, and erosion from Cambrian to the present. 

Preserved Mesozoic and older sedimentary rocks 

in the basin formed as, part of widespread regional 

depositional systems. Paleozoic rocks consist of a thick 

sequence of marine clastics, carbonate rocks, and evaporites overlain by eolian and fluvial sandstones and mudstones. Mesozoic strata, accounting for more than 60 

percent of the sedimentary basin fill, were deposited in a 

variety of fluvial, lacustrine, and marine depositional 

environments. Tertiary continental fluvial and lacustrine 

rocks were deposited within the San Juan Basin but are 

preserved only in its northern part. 

The San Juan Basin assumed its present 

structurally asymmetric form during the Laramide orogeny in Late Cretaceous to Eocene time. The structural 

basin is bounded on the northwest and north by the 

Hogback monocline, on the northeast by the Archuleta 

anticlinorium, on the east by the Nacimiento uplift, on 

the south by the Zuni uplift, and on the west by the 
Defiance Laramide-age uplift. Basinward-directed thrust 

faults underlie the Hogback monocline and parts of the 

Nacimiento uplift. The configuration of the subsurface 

faults, together with numerous folds and normal faults 

around the southern, western, and northern margins of 

the basin, suggests that the basin was formed by northeastward compression during northeast rotation of the 

Colorado Plateau. Major faults and folds along the 

eastern side of the basin are part of a wrench-fault system 

along which a small amount of right-lateral movement 

may have occurred. Interpretation of more than 1,000 mi 

of reflection seismic ·lines from the basin suggests the 

presence of numerous northwest- and northeast-oriented 

faults bounding basement blocks of various sizes. 

Movement on these faults and on basin-bounding uplifts, 

recurrent during the geologic history of the basin, 

influenced the rates of sedimentation, the distribution of 

facies, and the preservation or erosion of rock. 

The San Juan Basin contains significant resources 

of coal, uranium, and oil and gas. Coal occurs only in 

Upper Cretaceous sequences deposited during major 

shoreline regressions and stillstands. Uranium deposits 

in the basin account for more than 50 percent of the 

Nation's uranium reserves; these uranium deposits are 

principally in Jurassic sandstone and limestone. Major 

oil- and gas-bearing strata include Cretaceous marine 

sandstone, Jurassic eolian sandstone, and Pennsylvanian 

carbonate rocks. Significant nonconventional 

hydrocarbon resources occur in low-permeability 

sandstone and in coal beds. 

Manganese Nodules and Microbial 

Fixation of Oxidized Manganese in the 

Huntley Meadows Wetland, Fairfax 

County, Virginia 

E.l. Robbins, J.P. D'Agostino, Virginia Carter, 

D.S. Fanning, C.J. Gamble, J. Ostwald, R.L. 

Van Hoven, and G.K. Young 

Observations of active processes in modern peatforming wetlands can be used to explain the origin of 

metals in coal deposits. One metal that is easy to track in 

the modern environment is manganese, because its oxide 

precipitates are black. The iron bacteria that oxidize 

manganese are morphologically distinct, and oxidized 

manganese can be readily identified with the redox dye 

leucoberbelin blue (LBB). 

The Huntley Meadows wetland in Fairfax County, 

Va., hosts an active Mn deposit. Manganese-rich ground 

water and streams enter the wetland; Mn accumulates in 

peat, coats rocks in stream riffles, and forms nodules in 

69 

soils that accumulate in streams. Manganese-binding 

activity can be shown for all the iron bacteria in the 

wetland. 

The > 800-acre wetland is one of many floodplain 

wetlands along the course of Dogue Creek, which flows 

into the Potomac River. The wetland is located in a 

meander cut into Cretaceous sedimentary rocks by the 

ancestral Potomac River. In the Pleistocene, the 

meander channel was filled with a basal gravel, overlain 

by impermeable clay and silt that serve as a confining 

layer for the modern wetland, and locally by peat as thick 

as 23 feet. 

In terms of vegetation, open ponds are colonized by 

pond weed and water starwort; marshes are dominated 

by soft rush and wool grass; shrub wetlands contain 

button bush, swamp rose, and lizard's tail; and forested 

wetlands are a mosaic of oak, maple, and sweet gum 

trees. Peat composed of the bog moss, Sphagnum, and 

plant litter are being actively deposited but not 

accumulating because of a fluctuating water table. 

No water budget has been measured yet for the 

wetland, but annual inputs include surface water, ground 

water, and an average 39 inches of rainfall. Surface pH 

measurements in an open pond and inflowing streams 

range from 5.8 to 7.4. The Mn content of ground and 

surface water was measured at two localities in April 

1989. At Mittendorf£ spring along Dogue Creek, the Mn 

content of an underlying sandy aquifer was 0.51 mg!L, 

and Mn content from surface water was 0.44 mg!L, as 

measured by direct current plasma atomic emission 

spectrometry. In Dogue Creek at our Telegraph Road 

bridge locality, the Mn content of an underlying sandy 

aquifer was 0.49 mg!L, and Mn from surface water 

measured 0.02 mg!L. 

Manganese oxide is precipitating and accumulating 

in the wetland. A fibric peaty muck at the surface 

contained 680 ppm Mn (dry weight, dw); at a depth of 

nearly 100 feet, a 3-inch sapric muck in a core contained 

870 ppm Mn (dw). Manganese oxide precipitates on the 

rocks of riffles of streams entering the wetland. Glass 

slides left in the riffles become coated with doughnutshaped polygonal precipitates on the holdfasts of the 

Mn-binding iron bacterium Leptothrix discophora. 

Manganese nodules accumulate in Deer Run, a 

tributary to Dogue Creek, and form in the surrounding 

soil. Initial estimates suggest that several hundred 

pounds of Mn oxide nodules are present in the soil and 

streams. Soil taxonomy classifies the Mn-rich hydric soil 

of the wetland as an Ochraquult; the nodules form in the 

transitional EB-BE horizon between a very dark grayishbrown (10YR 3/2) silt loam A horizon and the gray (10YR 

6/1) silty clay of the Btg horizon. Knobby manganese oxide 

nodules as large as 3 em in diameter have been collected 

from the transition zone. Glass slides left in this 

transition zone were colonized by cocci and bacilli and 
became coated with soil particles, some of which tested 

positive for manganese oxide. Creek nodules, which 

probably formed as a lag concentrate from the 

surrounding soils, are rounded, pisolitic, and no larger 

than 1 em in diameter. They can be characterized 

chemically as ferromanganese and have buff, iron-rich 

rims surrounding black, manganese oxide cores. The 

creek nodules are amorphous to poorly crystalline, as 

shown by X-ray diffraction, and are composed of the 

barium-rich psilomelane, romanechite (Ba, 

Mn + 2

)3(0,0H)6Mns0 16· Glass slides left in the creek 

become competely coated with the black Mn oxide 

precipitates of Leptothrix discophora. Manganeseoxidizing activity, as shown by the bright-blue color of 

LBB, is present in the other iron bacteria as well, 

including Leptothrix ochracea, Leptothrix/Sphaeroti/us sp., 

Siderocapsa sp., and Gallion ella ferruginea. 

The manganese cycle is complex, and many details 

remain to be determined. From this study of microbial 

populations and hydrological inputs, we conclude that a 

metal such as manganese can be incorporated into peat 

during deposition and therefore be inherited by the 

ensuing coal. 

Microbially Mediated Fixation of 

Uranium, Sulfur, and Iron in a 

Peat-Forming Montane Wetland, Larimer 

County, Colorado 

E.l. Robbins, R.A. Zielinski, J.K. Otton, D.E. 

Owen, R.R. Schumann, and J.P. McKee 

Uranium and sulfur create major environmental 

concerns as problem elements in coal. To study processes 

that contribute to the initial fixation of these elements in 

peat, we selected a modern, minerotrophic, peat-forming 

environment. Microbiological, palynological, and 

geochemical techniques were used to characterize the 

biogeochemical conditions that affect the mobility and 

immobility of uranium, sulfur, and iron in the wetland. 

The Boston Peak wetland is a fen/carr complex 

located at 8,800 feet elevation in the Colorado Rockies. 

The 8-acre wetland lies along the floor of the glaciated 

upper Laramie River valley and is surrounded by faulted, 

uraniferous, granitic and metamorphic rocks of Early 

Proterozoic age, mineralized fault zones, and Tertiary 

volcaniclastic rocks. The wetland is fed by metal-bearing 

ground water, and uranium has accumulated in Pleistocene and Holocene peat and lacustrine sediments in 

the subsurface. 

Vegetation of the central fen is dominated by 

sedges ( Carex spp.) and the spike rush (Eleocharis rostellata). Vegetation of the marginal carr is dominated by 

70 

willow (Salix planifolia), but birch (Betula glandulosa) is 

also common. Coring in the wetland has revealed a 

sedimentary section as much as 35 feet thick, composed 

of a basal glacio-lacustrine clay as a confining layer and 

an overlying permeable peat, as much as 13 feet thick, 

composed predominantly of sedge and rush remains. Ash 

content of the peat ranges from 10 to 25 weight percent; 

the mean value is 15 percent. Pine and spruce pollen is 

abundant in the peat. Diatoms are particularly abundant 

through the basal section of the peat and most of the clay. 

Although the maximum uranium content of the clay is 

about 150 ppm, the uranium content of the peat varies 

from a few ppm to 3,300 ppm near spring sources. 

Ground water dominates the water budget of the 

Boston Peak wetland. Seeps feed the wetland along the 

east and south edges, and ground water upwells in five 

spring pools. Spring pools provide the best samples of 

input ground water (S04 4.0-6.5 ppm, U 20-83 ppb, total 

Fe 0.02-0.20 ppm, pH 6.95-7.65, DO (dissolved oxygen) 

2-3 ppm). Well waters sampled from the base of the peat 

represent ground water modified by residence in the 

reducing environment of the subsurface (S04 0.4-4.7 

ppm, U < 0.1-1.5 ppb, Fe 0.07-5.8 ppm, pH 6.15-7.0, 

DO <0.1 ppm). 

The identified microbial populations were those 

having distinct morphologies or distinct mineral 

precipitates. Many of the bacteria use iron and sulfur as 

important energy sources. Iron-oxidizing bacteria 

include: Leptothrix discophora that forms floating surface 

films of iron oxide; L. ochracea that forms red flocculates 

of ferrihydrite; and Siderocapsa sp. that precipitates iron 

oxide in organic-matter-rich standing water. Sulfuroxidizing bacteria include: Thiothrix sp., microaerophilic, 

white, filamentous bacteria in the suboxic zone at 10 em 

water depth in one spring pool; and Lamprocystis sp., 

purple anoxyphotosynthetic sulfur bacteria in another 

spring pool. We did not determine the physiological 

characteristics of the microbial populations that reduce 

uranium, sulfur, and iron; but from anoxic ground water 

in piezometers, bacilli, cocci, and rare filamentous 

bacteria wer~ filtered and counted; counts ranged from 

2. 7 X 105 to 1.65 X 106 cells/mL. One spring pool had 

sulfur-oxidizers in the near-surface waters. Below that 

surface, short, curved, black-rimmed rods (Desulfovibrio?) were collected from the anoxic, HzS- and 

organic-matter-rich muds. 

The cycles involving uranium, sulfur, and iron are 

entwined through microbial oxidation, reduction, and 

degradation. Data from four cores of peat and clay show 

that iron oxide occurs with pyrite at almost all depths, 

which suggests that the oxide precipitates of iron bacteria 

may serve as iron sources for pyrite production by 

microbial reducers. Near the spring pool that records the 

highest uranium concentration in peat, framboidal pyrite, 

resulting from the action of sulfur-reducing bacteria, is 
present in samples collected at depths greater than 36 

inches. Fission track radiographs of sliced peat indicate 

that uranium (1) is most abundant at depths where pyrite 

is abundant, (2) is primarily located on organic matter, 

and (3) is not concentrated immediately adjacent to 

authigenic pyrite. 

Because the plant parts in the peat of these 

intervals are particularly degraded, we postulate that 

uranium reduction is microbially mediated but in a 

complex manner. Because anaerobes were not studied, 

direct reduction cannot be ruled out. Indirect reduction 

is interpreted from observations on the state of 

preservation of plant parts and from the presence of 

pyrite. Partial decomposition of organic matter by 

microbial degraders can act to produce organic 

compounds serving as carbon sources for heterotrophic 

sulfur-reducing bacteria and providing sites for uranium 

adsorption. The local microbial production of H2S from 

upwelling so4 -bearing ground water can reduce 

previously sorbed U (VI) and continually added dissolved 

U(VI) to relatively insoluble U(IV), further 

immobilizing and concentrating uranium in the peat. 

Structural and Basement-Lithological 

Implications of Gravity and 

Seismic-Reflection Data Across the 

Central Powder River Basin from the 

Black Hills to the Bighorn Mountains 

S.L. Robbins and J.A. Grow 

The most conspicuous features on a colored 

complete Bouguer anomaly (CBA) gravity map of the 

central Powder River basin (lat 44°-45° N., long 

104°-108° W.) are: (1) a northwest-trending gravity high 

(-106 mgal) over the Bighorn Mountains, (2) a northtrending gravity low (-186 mgal) over the deepest part of 

the basin (western edge), (3) a small, arcuate gravity high 

(-108 mgal) over the central part of the basin, (4) a small 

gravity low (-136 mgal) east of (3), and (5) a gravity high 

( -84 mgal) over the Black Hills near the northeast corner 

of Wyoming. These features and the following 

interpretations are based on several map compilations at 

the scale of 1:500,000: (a) complete Bouguer gravity 

anomalies in color, (b) isostatic residual gravity 

anomalies in color, (c) horizontal gravity-gradient 

anomalies in color, (d) residual-intensity aeromagnetic 

anomalies in color, (e) structure contours of the basin 

area. The maps are augmented by several profiles: (a) 

gravity and magnetic modeling of the thrust fault on the 

eastern side of the Bighorn Mountains, (b) an east-west 

gravity and magnetic model across the Powder River 

basin, and (c) two seismic-reflection profiles from 

Chevron USA, Inc. 

71 

The highest part of the gravity high over the 

Bighorn Mountains is situated west of the 

topographically highest part of the mountain range. 

Modeling of this offset relationship along with modeling 

of aeromagnetic profiles and the high-quality seismicreflection profiles along the east flank of the Bighorn 

Mountains provide strong evidence that the Precambrian 

rocks of the mountain range have been thrust eastward, 

along a low-angle fault (dipping 20°-30°), several to 10 or 

more kilometers over sedimentary rocks within the 

Powder River basin. Modeling of the gravity data does 

not require density influences outside of the crust and 

can easily accommodate a westward flattening of the 

thrust fault into the middle or lower crust. When isostatic 

corrections are applied to the CBA data, this large gravity 

high over the Bighorns becomes even larger (by 25-30 

mgals ), suggesting that these mountains are rootless and 

not in local isostatic compensation. 

Borehole and seismic data indicate only gentle 

westward dips for the strata within the central part of the 

basin. The gravity high in area (3), therefore, is probably 

caused by significant lateral differences in the densities of 

the Precambrian basement rocks that are related to 

basement lithologic variations. Aeromagnetic patterns 

within the basin also support this interpretation. 

On a regional scale, the CBA values decrease from 

east to west probably as a result of: (a) westward 

thickening of the sedimentary basin-fill, and (b) westward 

increase in depth to base of the crust. When isostatic 

corrections are applied to the gravity highs over the 

Bighorn Mountains and the Black Hills, the corrections 

of the highs over the Bighorns are much greater; 

therefore, the residual values of these two highs become 

more equal than the CBA values, suggesting that, on a 

more regional scale, the area is in isostatic equilibrium. 

Characterization of Hydrocarbon 

Reservoirs in Eolian Sandstones 

C.J. Schenk 

Eolian sandstones can be composed of eoliandune, clastic sabkha/interdune, and sand-sheet facies, 

and can be intercalated with extra-dune (fluvial, tidal, 

evaporite) facies. Successful reservoir development and 

improved hydrocarbon recovery require an 

understanding of the vertical and lateral distribution of 

the different facies and their fluid-flow properties. 

Generally, eolian-dune sandstones are the best 

hydrocarbon reservoirs, whereas interdune/sabkha, sandsheet, and extra-dune facies can be barriers to fluid flow 

largely because of depositional textures and diagenetic 

alterations, some of which are early. 
Eolian-dune sandstone is generally well sorted, and 

comprises a coset of sandflow cross-strata and eolian 

ripple strata. The sandstones can range from a simple 

stacking of sets of cross-strata, to those in which the 

internal geometry is complicated by several scales of 

bounding surfaces. Eolian-dune sandstones generally 

exhibit little or no early diagenesis. 

Clastic sabkha/interdune sandstones are not as well 

sorted as dune sandstones, and are more irregularly 

bedded. Structures common to sabkha/interdune 

sandstones include thin sets of eolian ripple strata, 

adhesion structures, irregular bedding, contorted strata, 

and thin, remnant foresets. Early diagenesis is common 

because of the association of these deposits with the local 

water table. Early diagenesis includes cementation by 

halite, gypsum, calcite, dolomite, aragonite, and silica. 

Early cements such as halite and gypsum can be 

pervasive, leading to a juxtaposition of cemented 

sabkha/interdune sands and uncemented eolian dune 

sands. Sand-sheet sandstones typically exhibit the same 

forms of early diagenesis as the clastic sabkha/interdune 

sandstones. These differences in early diagenesis persist 

and influence the pathways of later diagenesis. 

Sedimentary Patterns on the Mid-Atlantic 

Continental Rise as Discerned by a 

GLORIA Sidescan Survey 

John S. Schlee and James M. Robb 

A detailed GLORIA sidescan survey (125,000 

km2

) of the continental slope and rise off the midAtlantic coast has revealed a complex association of 

depositional features and transport channels on the 

upper continental rise. The relatively flat upper rise 

deepens from 2,000 to 4,000 m over a distance of 150 km. 

No submarine fans mark the base of the slope; instead, 

the upper rise has three large triangular zones where 

sediment conduits converge seaward in what we term 

"gather areas" (Norfolk, Baltimore-Toms, and Accomac). These are mainly sediment transport pass-through 

areas where many submarine canyons converge, or die 

out, or lose their identity at the base of the slope, in a 

broadly triangular region. The apices of the "gather 

areas" lead into major channelways that cross to the 

lower rise. High-resolution profiles of the gather areas 

show multilayered drape and zones of hyperbolic returns 

where minor channels are cut. The Accomac and Norfolk 

gather areas are associated with smaller submarine 

slides, now largely buried. 

Irregular areas of hemipelagic drape that lie 

between the gather areas are uniform regions of low 

back-scatter (dark gray) on the GLORIA mosaic (fig.1); 

72 

in a few areas, the sediment drape is finely gullied and 

occurs adjacent to major channelways. High-resolution 

seismic profiles are marked by gently rolling multilayered 

signature. 

Channelway systems traverse the rise in broadly 

curving bands, within which are narrow, active channels. 

Some of the channelways, like the Hudson, are fairly 

direct pathways to the lower rise and contain only a few 

meanders. Other channelways at the apex of gather areas 

are as much as 9 km wide and extend toward the lower 

rise in broad conduits that are well defined 

topographically. 

The Albemarle-Currituck slump-debris flow is a 

complex tongue-shaped mass off North Carolina as much 

as 40 km wide that extends 120 km seaward of the base of 

the slope. The flow appears as light-gray discontinuous 

streaks on the mosaic. The varied acoustic texture on the 

mosaic is interpreted to represent a complex of slides, 

slumps, and debris flows. Seismic-reflection profiles in 

the shallower part of the complex show closely spaced 

diffuse hyperbolae that indicate bottom relief of about 

300m. 

The GLORIA images show the upper rise 

topography to be dominated primarily by offshoredirected processes that are probably of Pleistocene and 

early Holocene age, when sea level was near the shelf 

edge. Evidence of contour-parallel processes is visible 

only in the seaward parts of the study area. For example, 

the Lower Rise Hills are an area of contour current scour 

covering at least 22,000 km2 on the lower rise off 

Virginia-North Carolina. The mosaic of this area shows a 

distinctly rippled surface marked by alternating bands of 

high and low reflectivity whose crests are 8-10 km apart. 

Prediction of Sandstone Porosity-An 

Extension of the Concept of 

Thermal Maturity 

James W. Schmoker and Timothy C. Hester 

The porosity of sandstones, which is roughly 40 

percent at the depositional surface, commonly decreases 

during burial. The decrease is frequently treated as a 

function of burial depth. However, depth is a position 

coordinate that may not reflect the effects upon porosity 

of variations in thermal and burial histories. An alternate 

approach is to consider porosity decrease during burial_ 

as a function of thermal maturity. Advantages of this 

approach are: (1) it takes into account variations in 

time-temperature histories and (2) the thermal-maturity 

measurements used to define porosity trends can also be 

used to characterize petroleum generation and 

destruction. The timing of porosity change and of kerogen and petroleum maturation can thus be linked. 
Figure 1 (Schlee). The GLORIA mosaic of the U.S. mid-Atlantic continental rise from the shelf edge (dark area to 

northwest) to the middle continental rise (in excess of 4,000 m water depth). 

Low, average, and high sandstone porosities can 

each be represented by an equation of the form 

r/> = ARo 8 , where r/> is porosity and Ro is vitrinite 

reflectance. B is a negative number. This result is derived 

from 131 measurement suites incorporating 4,353 

73 

individual porosity measurements. Diverse sandstone 

facies and geologic settings are represented. The data 

span a maturity range of Ro = 0.25-1.7 percent. 

Plots of porosity versus Ro for the lOth, 25th, 50th, 

75th, and 90th porosity percentiles of each measurement 
10~----------~------~----~--~--~~ 

9 

8 

7 

6 

5 

-

C/)3 

0 

a: 

0 

a.. 

2 

', 

' ' 

' ' ' 

' ' 

' ' ' 

' ' 50th ' 

' ' ' ' 

\ 

\ 

\ 

25th ' 

' ' ' ' 

' ' ' ' ' \ 

\ 

\ ' 1Oth 

\ 

\ 

' \ 

\ 

\ 

' ' ' ' ' 

' ' ' ' ' ' ' 

' ' ' ' 

' ' ' ' ' 1~------------~------~----~~--~--~~ ' 

1 2 3 4 5 67 

VITRINITE REFLECTANCE (

0

/o) 

Figure 1 (Schmoker). Extrapolation of regression lines, fit to 10th, 25th, 50th, 75th, and 90th percentiles of sandstone 

porosity distributions, to thermal maturities characteristic of deep portions of sedimentary basins. Note that remarkably high 

porosities, which may be of great exploration importance but which represent a very small fraction of sandstones overall, are 

not represented by this figure. 

74 
suite form subparallel trends, with correlation 

coefficients of roughly r=-.7, from which regional 

porosity predictions may be extrapolated. Regression 

lines for the lOth through 90th porosity percentiles are 

projected in figure 1 (p. 74) to thermal maturities as high 

as Ro = 7 percent. These projections, taken together, 

predict the typical porosity distribution of deeply buried 

sandstones. As such, they are useful for basin modeling 

and as a framework against which to compare local 

porosity measurements. 

Variations in Facies Architecture Related 

to Sequence Stratigraphy of the 

Turonian-Campanian Strata, Kaiparowits 

Plateau, South-Central Utah 

Keith W. Shanley and Peter J. McCabe 

The various facies developed within the Straight 

Cliffs Formation of the Kaiparowits Plateau have been 

studied in outcrop and placed within a sequencestratigraphic framework. The strata are arranged in 

geometric patterns that can be related to lowstand, 

transgressive, and highstand systems tracts. This 

interpretation provides a new perspective to regional 

chronostratigraphic and lithostratigraphic relationships 

of Turonian through lower Campanian strata for 

southern Utah. 

Shoreface deposits of the Tropic Shale and the 

overlying Tibbet Canyon Member of the Straight Cliffs 

Formation record progradation of highstand and late 

highstand systems tracts. Extensive reworking of the 

upper shoreface deposits by tidal processes may be 

explained by the relatively slow rates of base level rise, 

which provided ample time for lateral migration of tidal 

channels. Coarse, laterally amalgamated fluvial clastics 

of the Smoky Hollow Member of the Straight Cliffs 

Formation are interpreted as braided river deposits. This 

transition from shoreface to braided river deposits 

represents an abrupt seaward shift in facies tracts due to 

an increased rate of base level fall. The lower portion of 

the Ferron Sandstone Member of the Mancos Shale to 

the east may be part of the resulting lowstand systems 

tract. 

Renewed base level rise is recorded within the 

Smoky Hollow by a vertical change from fluvial and 

floodplain deposits to tidally influenced sandstones 

capped by a ravinement surface characterized by a thin 

pebble lag. These strata and the upper portion of the 

Ferron Sandstone Member to the east compose the 

transgressive systems tract. A thin shark-tooth lag, a few 

meters above the ravinement surface, is thought to mark 

a condensed section recording maximum rate of water 

deepening. 

75 

Subsequent reduced rates of base level rise 

resulted in vertical aggradation of the overlying John 

Henry Member of the Straight Cliffs Formation which 

forms an early highstand facies tract. Aggradation of 

fluvial sediments is recorded in the western part of the 

plateau whereas vertical stacking of shoreface sandstones 

is characteristic of the eastern margin. The central part of 

the plateau was the site of major coal accumulation. Most 

of the fluvial strata show a high ratio of overbank to 

channel deposits. In the lower part, however, there is a 

low ratio of overbank to channel deposits which 

corresponds to a small forward step in the shoreface 

sandstones to the east, indicating a period of somewhat 

slower base level rise. In contrast to the Tibbet Canyon 

Member, most shoreface deposits of the John Henry 

Member show little evidence of reworking by tidal 

channels, presumably because of the more rapid rates of 

base level rise. 

The John Henry Member is unconformably 

overlain by the laterally amalgamated, coarse fluvial 

sandstones of the Drip Tank Member of the Straight 

Cliffs Formation. The unconformity represents removal 

of increasing amounts of strata to the west. The braided 

river deposits of the Drip Tank resulted from a major 

lowering of base level during the Campanian. 

Impact of Drilling off Key West, 

Florida-Where's the Beef? 

Eugene A. Shinn 

Geological and biological assessment of eight 

nonproductive offshore drill sites off South Florida 

revealed both positive and negative environmental 

impacts. Measurable impacts at all sites were of 

mechanical origin and limited to small areas adjacent to 

the borehole. 

Environments near Key West, where six wells were 

drilled between 1959 and 1961, include coral reefs, sea 

grass, live bottom and rippled carbonate sands. Two 

modern wells off Fort Myers (1981 and 1986) were 

drilled in deep water (53 and 70 m). The deeper site was 

on a surficial algal/sponge community, whereas the other 

was on a relatively barren sand with scattered spongeencrusted rocky outcrops. (Table 1 provides additional 

site data.) 

Positive impact is limited to the "artificial-reef 

effect." Abundant debris discarded at sites on rippled 

sand was encrusted with corals and algae not present 

before drilling. Numerous species of fish and crustaceans 

reside among casing, cables, discarded core, and other 

materials that were routinely dumped overboard before 

enactment of OCS dumping regulations. 
Table 1 (Shinn). Well site data, offshore Florida drill sites 

Loran Lease Well name Lat./Long. CTDs block 

SL 1011 No.2 13887.9 24.32.07 State 

43748.5 82.06.25 1011 

SL 1011 No.3 13887.9 24.32.07 State 

43748.5 82.06.25 1011 

SL 826Y No.1 13905.4 24.37.05 State 

43729.1 82.02.14 826Y 

OCS 0665 No.1 13845.7 24.27.06 ocs 

43826.8 82.21.40 Block 28 

OCS 0674 No. 1 13826.4 24.26.01 ocs 

43867.9 82.29.18 Block 46 

OCS 0672 No.1 13809.8 24.25.13 ocs 

43903 82.36.02 Block 44 

OCS G4950 No. 1 13854.67 26.18.37.98 ocs 

30348.52 83.42.10.99 Block 622 

OCS G3906 No. 1 13978.88 26.49.27.19 ocs 

30587.78 83.24.33.20 Block 144 

Negative impact resulted where drill rig legs and 

anchors impacted coral bottom, and at one site the 

bottom was altered when a barge load of pea gravel was 

dumped to level the bottom. Approximately 1 acre of 

gorgonian and sponge hardbottom was destroyed by the 

pea gravel. A new community of fleshy algae now grows 

on the pea gravel. At the same site several dozen bags of 

cement were piled over the well head. The cement bags 

support 8 species of corals and provide a habitat for 25 

species of fish. 

The most severe and long-lasting impact occurred 

where a 14-legged jackup rig (site OCS 0665 No. 1) 

drilled on coral reef bottom in 1960. In addition to the 

sand-filled 4.5-m-diameter "footprints," two > 30-

m-long anchor scars remain. The total amount of 

impacted bottom is 406m2 or approximately 1!10 acre. 

Sand in the impacted areas has prevented coral and 

gorgonian recruitment for the past 30 years. However, 

diversity and numbers of corals and gorgonians in a 

10-m2 quadrant bordering the borehole are the same as 

in a control site 1 km from the borehole. No positive or 

negative impacts could be detected where a floating rig 

was used to drill on a coral reef. Although all sites may 

have been initially impacted by drill mud and cuttings, no 

evidence of their effects could be detected in 1988. 

76 

Date Rig Water Well 

depth depth Lessee drilled type (m) (m) 

1961 Barge 5 2,354 California Co. 

1962 Pontoon 5 3,917 California Co. 

1959 Unknown 5 4,481 Gulf Oil Corp. 

1960 Jackup 11 4,662 Gulf Oil Co. 

1961 Jackup 23 2,399 Gulf & Calif. Co. 

1961 Barge 20 1,429 California Co. 

1986 Jackup 70 3,216 Shell Oil Co. 

1981 Jackup 53 3,464 Gulf Oil Corp. 

Drill mud and cuttings were not apparent at either 

of the deep-water sites drilled in the 1980's. Neither 

cuttings nor drill mud was apparent at OCS G4950 No. 1 

drilled in 70 m of water in 1986, 2.5 years before our 

observations. The most obvious impact consisted of a 

1-m-high, 10-m-diameter mound of grout surrounding a 

1-m-diameter borehole. Large fish lived in the borehole 

and the site was enveloped by a cloud of small sardinelike 

fish. Some debris was present, the most obvious of which 

were dozens of used welding rods. 

The other deep-water site (53 m), drilled in 1981, 

consisted of a 1-m-diameter borehole centered on a 

patch of sponge-encrusted hardbottom. Two very large 

groupers occupied the hole and again the area was 

enveloped in clouds of small fish and schools of 1-m-long 

amberjacks. Debris was less obvious and no grout mound 

or cuttings pile was present. At both deep sites, the 

borehole and debris had created an artificial reef. 

The purpose of our study was to determine what 

effects can be predicted during future drilling in tropical 

environments. We conclude that noticeable damage from 

offshore exploratory wells drilled on or around coral 

reefs will be of mechanical origin. Anchors and platform 

legs do impact on the environment; proper selection of 

drill sites can greatly reduce such damage. Because the 

only visual evidence of drilling at sites drilled on sandy 
bottom was caused by discarded debris, I conclude that if 

no debris is thrown overboard there will be no lasting 

effect of drilling, assuming no blowouts or drilling 

accidents. In fact, it would have been impossible to verify 

six of the eight sites had debris been absent. Because 

impacts are largely mechanical, it seems likely that 

offshore wells can be drilled within a few meters of reefs 

without causing lasting harm. 

Western Tight Gas Reservoirs-Resource 

Potential and Development Constraints 

Charles W. Spencer, Ben E. Law, and 

Ronald C. Johnson 

In 1985 the U.S. Congressional Office of 

Technology Assessment analyzed the availability of 

natural gas to the year 2000 and beyond. They concluded 

that tight gas reservoirs, located mostly in the western 

United States, had the greatest potential to replace 

declining conventional gas reserves. Tight reservoirs in 

the U.S. are currently producing about 1 TCF (trillion 

cubic feet) of gas per year. This volume is about 1/16 of 

total U.S. production. 

The USGS, in cooperation with the U.S. 

Department of Energy (DOE), is conducting research on 

selected western tight gas basins and areas. Estimates of 

gas in place and recoverable gas have been made for 

three basins and areas: the northern Great Plains, the 

Piceance basin in northwest Colorado, and the Greater 

Green River basin in southwest Wyoming and northwest 

Colorado. The Greater Green River basin tight gas 

assessment, made in 1989, is the most recently completed 

evaluation. An assessment of tight gas resources in the 

Uinta basin in northeast Utah is currently in progress. 

The Greater Green River basin tight gas-bearing 

interval is mostly overpressured and is as thick as 14,000 

ft. The prospective rocks consist of sandstone, mostly 

Cretaceous in age but including some of early Tertiary 

age. The gas-bearing intervals were subdivided into five 

plays, and only gas-bearing sandstones more than 10 ft 

thick were included in the assessment. Several economic 

and technologic scenarios were used to estimate 

recoverable tight gas volumes in the Greater Green River 

basin. The most conservative estimate was made 

assuming state-of-the-art current technology and a gas 

price of $5/MCF (thousand cubic feet) in 1987 dollars. 

Using these criteria, the aggregated recoverable gas 

estimates for the five Greater Green River plays range 

from 27 to 148 TCF. The arithmetic mean estimate is 73 

TCF. 

The Piceance basin tight gas resource assessment, 

made in 1987, estimated a recoverable gas volume, using 

77 

current technology, ranging from 8.46 to 20.65 TCF with 

an arithmetic mean of 13.42 TCF. 

Recovery of much of the gas from tight reservoirs is 

heavily constrained. The two most significant constraints 

are gas price and recovery technology. Special incentive 

gas prices in the early 1980's exceeded $5/MCF in some 

areas of the U.S. These incentive prices encouraged a 

high level of exploration and development activity for gas 

in these low-quality reservoirs. Conversely, the current 

low gas prices have strongly discouraged tight gas 

research and development. 

Major advances are needed in recovery technology 

in order to improve the productivity of these lowpermeability reservoirs. Hydraulic fracturing is presently 

the most common method of reservoir stimulation, but 

this technique was developed approximately 40 years 

ago. More innovative drilling and completion methods 

need to be developed and tested, such as horizontal and 

inclined well drilling. New methods to reduce or prevent 

formation damage need to be tried. 

Based on these assessments, tight reservoirs appear 

to be one of the best future sources of gas and should be 

a key factor in the Nation's energy and economic future. 

Diagenesis of Organic Matter and 

Sulfur in Sapropel and Peat from 

Mud Lake, Florida 

E.C. Spiker, P.G. Hatcher, V.J. Comer, 

A. L. Bates, and S.A. Stout 

A study of Mud Lake, a small, shallow freshwater 

lake located in north-central Florida, was undertaken to 

further our understanding of the chemical changes 

occurring in peat during early diagenesis. The lake 

sediments are particularly interesting because they 

record a significant change in lake vegetation. The 

sediment grades from a gelatinous algal sapropel into a 

highly degraded aquatic Nymphae a peat at approximately 

2.5 m depth, and to a fibrous Mariscus peat at 

approximately 3 m depth. The sapropel was studied in 

the 1960's by Wilmot Bradley, who considered the sapropelic deposit to be analogous to the organic matter in oil 

shale. 

Our recent study mainly utilized solid-state 13C 

NMR (nuclear magnetic resonance) to determine the 

bulk organic chemistry, and stable isotopes were used as 

natural tracers. The total organic carbon content ranges 

from about 30 to 45 percent. The carbohydrate carbon 

content decreases and lignin and paraffinic carbon 

contents increase with depth in the sapropel and Nymphaea peat. This major change in the bulk chemistry of 

the organic matter reflects the degradation of labile 
material and the selective preservation of the more 

resistant aromatic and aliphatic (paraffinic) components. 

The carbohydrate content increases in the Mariscus peat, 

which is more fibrous and apparently better preserved 

than the overlying Nymphaea peat. 

The stable carbon isotope content shows a strong 

correlation with the carbohydrate carbon content, 

decreasing nearly 8 per mil with decreasing 

carbohydrates in the sapropel and Nymphaea peat. This 

correlation may be due, in part, to the loss of 13Cenriched carbohydrates, as studied in 1984 by Spiker and 

Hatcher. However, more than half this decrease in the 

carbon isotope composition is due to the change from 

algae to herbaceous plants, which also produced a large 

relative increase in lignin content in the Nymphaea peat. 

The total sulfur in the sediment is moderately high, 

especially considering that this is a freshwater lake. The 

source of the sulfur is presumably sulfate from local 

streams and ground water. The sapropel smells of H2S. 

Total sulfur content increases systematically from 2 

percent in the near-surface sapropel to about 6 percent at 

1.5 m depth and decreases to about 4 percent at 3 m 

depth in the Mariscus peat. The sulfur appears to be 

concentrated in the sediment as a result of the loss of 

labile organic matter. Forthcoming analyses of the forms 

and isotopic composition of the sulfur should help 

determine the origin and mode of sulfur formation. 

Age, Facies, and Depositional 

Environments of the Lower Miocene 

Lospe Formation, Santa Maria Basin, 

Central California 

Richard G. Stanley, Samuel Y. Johnson, John 

D. Obradovich, Michele L. Tuttle, Mary Lou 

Cotton Thornton, David R. Vork, Mark V. 

Filewicz, Mark A. Mason, and Carl C. Swisher Ill 

The Lospe Formation is an 800-m-thick sequence 

of sedimentary and minor volcanic rocks that occurs at 

the base of the petroliferous Neogene section of the 

Santa Maria basin of central California. We are 

conducting a multidisciplinary study of the stratigraphy 

and sedimentology of the Lospe in its type area in the 

Casmalia Hills. Our preliminary results shed new light on 

long-standing problems concerning the age and 

depositional setting of the Lospe and provide additional 

insights into the early Neogene history and paleogeography of the Santa Maria area. 

Until now, the age of the Lospe Formation has 

been constrained by the age of the underlying Jurassic 

ophiolite and the overlying lower Miocene Point Sal 

Formation. We have discovered palynomorphs of early 

78 

Miocene age in the upper 200 m of the Lospe and 

calcareous benthic foraminifers of earliest Miocene 

(Saucesian) age in the uppermost 15m of the Lospe and 

lowest 2 m of the Point Sal Formation. The lower part of 

the Lospe apparently lacks fossils but contains several 

horizons of pyroclastic crystal-vitric tuff that we are 

attempting to date isotopically. 

The Lospe has long been considered to be entirely 

nonmarine in origin. However, new fossil discoveries and 

detailed analysis of sedimentary facies indicate that the 

Lospe accumulated in an orderly succession of paleoenvironments including alluvial fan and fan-delta, lake or 

restricted coastal embayment, and shallow marine shelf. 

Alluvial fan and fan-delta facies within the basal 

part of the Lospe are up to 200 m thick and consist of 

reddish-brown and greenish-gray conglomerate and 

sandstone with minor mudstone and tuff. Many of the 

conglomerate clasts are angular, suggesting rapid firstcycle erosion from nearby fault -bounded uplifts of Mesozoic and Paleogene sedimentary and igneous rocks. 

Conglomerate clast compositions and paleocurrent 

directions suggest that this part of the Lospe Formation 

was deposited in at least two sub-basins separated by an 

east-west-trending paleohigh of Jurassic ophiolite 

located approximately in the same position as the 

present-day Point Sal Ridge. 

The alluvial fan and fan-delta deposits grade 

upward into a 600-m-thick sequence of interbedded 

greenish-gray sandstone and mudstone that accumulated 

in a subaqueous environment, most likely a lake or 

coastal embayment with restricted connections to the 

ocean. Many of the sandstone beds are sheetlike and 

normally graded, and appear to have been deposited by 

turbidity currents. The associated mudstones contain 

sparse marine microfossils including dinocysts, 

foraminifers, radiolarians, and diatoms. Lenticular beds 

of pyroclastic tuff, as thick as 20 m, occur sporadically 

throughout this sequence; in places, the tuffs incorporate 

blocks of Jurassic ophiolite up to 50 m long and 20 m 

across. 

Near the top of the Lospe Formation is a 5-m-thick 

bed of amalgamated, plane-laminated to bioturbated, 

fine-grained sandstone that can be traced laterally at 

least 6 km. This sandstone is underlain and overlain by 

mudstones bearing outer shelf to upper bathyal benthic 

foraminifers and is interpreted as a storm-generated 

shelf deposit. About 3 to 5 m above this sandstone, the 

characteristic gray-green mudstones of the Lospe are 

sharply overlain by black fissile shale of the Point Sal 

Formation, recording an abrupt change from a welloxygenated marine shelf to an oxygen-poor, deeperwater slope environment. 

Overall, the Lospe Formation provides a clear 

record of progressive deepening, active faulting, and 

regional volcanism during the earliest stages of formation 
of the Santa Maria basin. This history is consistent with 

several competing tectonic models that variously explain 

the origin of the basin as the result of regional extension, 

regional transtension, local pull-apart rifting, or local 

tectonic rotation of small crustal blocks. 

liquefaction Potential of Facies of the 

Wyodak-Anderson Coal Bed, 

Powder River Basin 

R.W. Stanton, P.D. Warwick, and S.S. Crowley 

Low-temperature carbonization yields, from a 

modified Fischer Assay, of selected samples from 

petrographically distinct facies have a positive correlation 

with the amount of humic matrix material ( cryptoeugelinite) in the Wyodak-Anderson coal bed of the Fort 

Union Formation (Paleocene, subbituminous). In 

contrast, the amount of total huminite, which varies little, 

does not correlate with carbonization yields. 

Facies within the Wyodak-Anderson coal bed were 

delimited on the basis of maceral compositions of 100 

samples from three localities in the Gillette Field, 

Wyoming. Four major classes of samples were indicated 

by cluster analysis. Facies were then defined on the basis 

of one or more of these sample classes. To evaluate the 

liquefaction potential of these facies, we selected 17 

samples to represent the six type of coal facies. 

Petrographic analyses were used to differentiate 

the samples by composition. Macerals on etched polished 

pellet surfaces were point-counted under white-reflected 

light and blue-light fluorescence. Relative response of 

the varieties to etching by acidified potassium permanganate solution facilitated identification of huminitemaceral varieties. In particular, structured huminite 

macerals ( crypto-humotelinite, crypto-detrogelinite, and 

crypto-corpohuminite) are more resistant to etching than 

the humic matrix material ( crypto-eugelinite ). 

Oil yields from Fischer Assays range from 0.7 to 

9.9 wt. percent on an as-received basis and from 0.8 to 11 

wt. percent on a dry basis. Crypto-eugelinite amounts 

vary from 17 to 58 percent on a dry, whole coal basis 

( dwc ). The plot of oil yield ( dwc) versus crypto-eugelinite 

(dwc) has a correlation coefficient of 0.72, a relation 

which is best shown by an exponential fit (fig. 1, p. 80). 

From these preliminary data, we infer that the more 

reactive and oil-yielding maceral is eugelinite, which 

resulted from chemical and physical degradation of plant 

cells and other, possibly hydrogen-rich plant parts. 

In the Gillette area, the Wyodak-Anderson coal 

bed consists of 12-15 km2 bodies that commonly exceed 

30 m in thickness. Samples from the margins and the 

base of the bed contain generally greater amounts of 

79 

structured huminitic materials than do samples from the 

upper and more interior parts of the deposit. Initial 

formation of the Wyodak-Anderson swamp deposits 

began with an accumulation of peat containing 

structured huminite premacerals. During later stages of 

accumulation, the margins of the swamp contained peat 

facies rich in structured premacerals. In the interior parts 

of the swamp, more degraded peat facies formed under 

wetter conditions, which probably were more suitable for 

the growth of peat-forming plants that were easily 

degraded. Swamp cessation was caused by lake flooding 

that deposited fine-grained sediments. 

Based on this model for peat development, the 

highest pyrolysis yields should be found in the more 

interior parts of the coal bodies. The optimal liquefaction 

yield would depend on the process used, but from this 

preliminary study, samples characterized by large 

amounts of degraded humic material ( eugelinite) should 

prove to be the most successful for liquefaction. Eugelinite can be also easily measured in higher rank coal by 

analysis of etched polished surfaces of coal. The eugelinite content of coal, therefore, may be an important 

parameter to determine if a coal bed were a source for 

petroleum. 

Is There a Future for 4.0 Trillion Tons of 

low-Sulfur Alaskan Coal? 

Gary D. Stricker 

With an ever-increasing interest in acid rain, the 

demand for and utilization of low-sulfur coal will 

increase. Alaska's coal resources have a unique position 

in the United States' overall coal resource picture and 

can only be described as enormous: 4.0 trillion tons of 

hypothetical onshore coal. Alaska's coal is also low in 

sulfur: mean total sulfur content of0.34 percent (range is 

0.06 to 6.6 percent, n = 262). Mean ash content is 10.9 

percent and mean apparent rank is subbituminous B. By 

contrast, Carboniferous coal of the Appalachian region 

and Interior Province has a mean total sulfur content of 

2.34 percent (range of 0.1 to 19.2 percent, n = 5,497); 

mean ash content of 11.16 percent; and a mean apparent 

rank of high-volatile A bituminous. Lower 48 Cretaceous 

and Tertiary coals have a mean total sulfur content of 

0.86 percent (range of 0.02 to 18.9 percent, n = 2,754); 

mean ash content of 11.97; and a mean apparent rank of 

subbituminous B. Thus, Alaskan coal's mean sulfur 

content is 2.5 times less than the mean for western U.S. 

coal and 6 times less than the mean for Carboniferous 

U.S. coal. 

A 1987 report by Wood and Bour lists 50 major 

and minor coal fields and occurrences of coal in Alaska. 
- 25 • c • 0 

.... 

-: 

ii • 

s 20 

'0 • a; 

">. 

0 

15 exponential line ~ • 

'0 

.I 

as 10 

E • 

;; ' .n • 

5 

• 

0 

10 20 30 40 50 60 

Crypto-eugellnlte (vol. o/o, whole coal basis} 

Figure 1 (Stanton). Low-temperature carbonization yields of Wyodak-Anderson coal samples. 

The bulk of Alaska's coal resources are in six major coal 

fields, which are (in order of decreasing economic 

potential) Nenana, Cook Inlet, Matanuska, 

Chignik-Herendeen Bay, North Slope, and Bering River. 

The Tertiary Nenana coal basin, containing the only 

active coal mine in Alaska, has the most economic 

potential. Mean total sulfur content in that coal is 0.24 

percent (range of 0.1 to 1.5 percent), mean ash content is 

9.9 percent, and mean apparent rank is subbituminous C. 

Resources are estimated to be 1 billion tons of identified 

coal and 2 billion tons of hypothetical coal. 

In the Cook Inlet region, two coal fields are of 

interest: Beluga and Kenai, in both of which coal is of 

Tertiary age. In the Kenai field, mean total sulfur content 

is 0.33 percent (range of 0.06 to 1.1 percent), mean ash 

percent is 14.3, and apparent rank is subbituminous C. 

Resources are estimated to be 320 million tons identified 

and 35 billion tons hypothetical. In the Beluga field, 

mean total sulfur is 0.18 percent (range of 0.08 to 0.33 

percent). Mean ash content is 16.4 percent and apparent 

rank is subbituminous C. This field contains 10 billion 

tons identified and 30 billion tons of hypothetical coal. 

The Tertiary Matanuska coal field has a mean total 

sulfur content of 0.45 percent (range of 0.2 to 1.5 

percent). Mean ash content is 12.3 percent and mean 

apparent rank is high-volatile A bituminous. Coal 

resources are estimated as 150 million tons identified and 

500 million tons hypothetical. 

Coal in the Chignik-Herendeen Bay fields is 

Cretaceous in age. Total mean sulfur content for these 

coal units is 0.82 percent (range 0.3 to 1.3 percent), mean 

ash content is 13.6 percent, and mean apparent rank is 

80 

high-volatile B bituminous. Resources are estimated to 

be 360 million tons identified and 3 billion tons 

hypothetical. 

The Alaskan North Slope has the largest estimated 

coal resources in Alaska. Coal ranges in age from 

Cretaceous to Tertiary. For the Cretaceous coal the total 

mean sulfur is 0.32 percent (range of 0.01 to 2.02 

percent), mean ash content is 10.4 percent, and mean 

apparent rank is subbituminous B. Resource estimates 

for the Cretaceous coal are 3.2 trillion tons of 

hypothetical coal. For the Tertiary coal, the total mean 

sulfur is 0.37 percent (range of 0.08 to 2.02 percent), 

mean ash content is 10.6 percent, and mean apparent 

rank is subbituminous C. No resource estimates are 

available for Tertiary coal. 

The Tertiary Bering River coal field has a mean 

sulfur content of 1.2 percent (range 0.4 to 5.22 percent). 

Mean ash content is 13.6 percent and apparent rank is 

semianthracite. Resources for this tectonically deformed 

coal field are 110 million tons of identified and 3.5 billion 

tons of hypothetical coal. 

Even though Alaska has 4.0 trillion tons of 

hypothetical low-sulfur coal, this resource has not been 

developed. Factors limiting coal development are: (1) 

increased shipping cost because of large distances to 

potential markets; (2) inhospitable climate during long 

and cold winters, which adds to the cost of mining; and 

(3) little infrastructure in areas where many coal fields 

are located. Unless the United States and world energy 

picture changes, this abundant resource will not be 

utilized in the near future. 
A Structural and Stratigraphic Transect 

Across the Florida Platform from the 

Deep Gulf of Mexico to the Deep Atlantic 

B. Ann Swift, William P. Dillon, 

Myung W. Lee, and Mahlon M. Ball 

The U.S. Geological Survey has synthesized data 

from multichannel seismic profiles, boreholes, 

submersible dives, and two seismic-refraction lines to 

develop a structural/stratigraphic transect across the 

Tampa Basin, the Florida peninsula, and the Blake 

Plateau basin. This transect spans a carbonate 

depositional province, from deep ocean crust on either 

side of the Florida peninsula, across steep erosional 

escarpments and broad, flat continental borderlands. The 

Cenozoic platform strata continue across the central 

Florida peninsula. Seismic profile TD-3 begins in the 

deep Atlantic basin, crosses the Blake Plateau basin, the 

Blake Escarpment, and the Blake Plateau. Lower 

Cretaceous rocks, exposed by erosion on the escarpment 

and sampled by DSRV ALVIN, provide fossil age-control 

that complements ages derived from well samples 

(DSDP 391 and 536 and COST GE-l). 

The offshore stratigraphy (Cenozoic and part of 

the Cretaceous) is carried across Florida by correlating 

biochronologic horizons with synthetic seismograms 

generated at six sites, using well-log data and 

extrapolating along multichannel lines. On the Gulf of 

Mexico side, seismic-reflection profile Mafla 15-16-17 

crosses the West Florida Shelf (near the St. Petersburg 

area) and extends beyond the Florida Escarpment to the 

deep Gulf of Mexico basin. 

Post-stack processing improved the seismic image 

of the platform features. A post-stack deconvolution 

filter was applied to the Mafia data and followed by 

migration. Line TD-3 (Blake Plateau basin) was treated 

similarly, except that a section near the Blake 

Escarpment was completely reprocessed to reduce 

multiple energy that obscured reflections immediately 

landward of the escarpment. Reprocessing also helped to 

better resolve a deep mantle(?) reflector seaward of the 

escarpment. The interpreted time sections were then 

depth-converted, using velocities from two oblique 

refraction lines and smoothed velocity functions. 

Early structure and stratigraphy of the Blake 

Plateau basin were controlled by the extensive Jurassic 

rifting and extension of continental crust associated with 

the opening of the North Atlantic. On Line TD-3, synrift 

and early postrift deposits (inferred red beds and other 

clastics) are overlain by predominantly carbonate 

platform deposits that filled the main basin during the 

thermal subsidence phase. The postrift stratigraphy is 

essentially flat, with pre-Upper Cretaceous horizons 

81 

terminating against a basement high on the landward 

edge. Erosion, concentrated on the seaward platform 

edge, created much of the present physiography. 

On the West Florida Shelf part of the transect, 

rifting associated with opening of the North Atlantic and 

the Gulf of Mexico is reflected in basement faulting. On 

the landward end of Line 17, the Paleozoic to Jurassic 

basement forms a fault-related monocline structure, 

which is draped by overlying Mesozoic and Cenozoic 

deposits. Farther seaward on Line 16, intrabasement 

reflections indicate a synclinal structure. Another 

basement monocline is evident seaward on Line 15, upon 

which Jurassic deposits onlap and thin toward the 

escarpment edge. 

Coal Resources in 

Sind Province, Pakistan 

Roger E. Thomas, Mohammed Riaz Khan, and 

Shafique Ahmed Khan 

Approximately 4.7 billion metric tons of coal, 

ranging from subbituminous C to lignite A in rank, has 

been estimated for the Sonda coal field and Indus East 

area in Sind Province, 80 km north of Karachi, Pakistan. 

This estimate was based on 34 exploratory drill holes 

completed between April1986 and February 1988 in an 

area of 1,583 km2

• The drilling was part of the Coal 

Resource Exploration and Assessment Program 

(COALREAP) of the Geological Survey of Pakistan, the 

U.S. Geological Survey, and the U.S. Agency for 

International Development. Ten coal zones within the 

Paleocene Bara Formation were identified. Most of the 

coal resources are in the Middle Sonda (2,200 million 

metric tons) and Inayatabad (780 million metric tons) 

coal zones. Together, these two coal zones contain 63 

percent of the total resources. 

Isopach maps of the thickest coal bed in each zone 

were constructed for the 10 identifiable coal zones in the 

Indus East area. Resource estimates, based on the 

thickest coal bed in each zone, reflect a conservative 

amount of coal in this area. In the Indus East area, for 

example, the thickest coal bed (2.40 m) in the Middle 

Sonda zone was found in drill hole UAK-15, 5 km west of 

Mulla Katiar; the thinnest coal bed (0.25 m) was found in 

drill hole UAK-12, 1 km west of UAK-15. Isopachs 

constructed for both coal bed thicknesses indicated a 

great variation in coal thickness over a relatively small 

area. The Inayatabad coal zone (approximately 60 m 

above the Middle Sonda coal zone) contains coal beds 

that range from 0.35 to 1.50 m thick and average 0.75 m 

thick. Isopachs drawn for the thickest Inayatabad coal 

bed revealed a nearly symmetrical thick coal deposit in a 
horseshoe-shaped area near the village of Tando 

Muhammed Khan and Chhari Dhand (lake]. The 

absence of coal in an area 9 km east-to-west and 24 km 

north-to-south suggests channels where the coal was 

eroded. 

Resources for the Indus East area were calculated 

for three reliability categories-measured, indicated, and 

inferred. The most reliable estimates are those for the 

measured category. Total coal resources are 

approximately 31,000,000 metric tons or about 2 percent 

of the total resources; indicated resources are 

241,000,000 metric tons or 14 percent of the total 

resources; and inferred resources are 1,414,000,000 

metric tons or 84 percent of the total resources, the least 

reliable resource category. This percentage distribution 

is due to the spacing of data points and the construction 

radii around the inferred category data point that are 

larger than the radii constructed for indicated or 

measured coal. 

Coal beds in the Sonda coal field and the Indus 

East area are difficult to correlate due to abrupt pinching 

out and swelling. They grade laterally to carbonaceous 

shale and rooted siltstone within 2 to 5 km. Seat rock can 

be sandstone, shale, or siltstone, and is commonly rooted. 

Most coal zones are separated by 5-10 m of interburden 

that can attain a maximum thickness of> 100m. Loose, 

unconsolidated sandstone and poor core recovery make 

interpretations difficult and coal bed correlations 

speculative. Closer spaced drill holes will clarify and 

significantly improve coal zone correlations in the Bara 

Formation. 

Analysis of 90 coal samples indicates a rank of 

subbituminous C to lignite A and average contents of 

13.7 percent ash and 3.6 percent sulfur. These coal 

analyses also indicate calorific values ranging from 6,000 

to 8,000 Btu on an as-received basis. 

Basin Analysis as an Exploration 

Tool-Paradigms Lost, Insights Gained 

Christine E. Turner-Peterson and 

Neil S. Fishman 

Advances in geology, as in all sciences, result from 

the testing and overturning of paradigms and the 

replacement of old theories with new. Paradigms are 

useful in seeking solutions to complex geologic problems 

because ''we have to start somewhere" in our analysis, 

and existing theory provides a convenient point of 

departure. Moreover, paradigms provide a framework 

within which to place what might otherwise be random 

observations. For example, a relatively new paradigm in 

geology is sequence stratigraphy, which provides a more 

systematic way to organize stratigraphic observations. 

82 

A problem with paradigms is that we become 

increasingly dependent upon the ready explanations they 

offer and find ourselves searching for data in support of 

the paradigm rather than treating the paradigm as one of 

many working hypotheses. The more a paradigm is cited 

in the literature, the more "correct" it becomes, and in 

the process the more difficult it is to overturn. So, 

although science advances by the overturning of 

paradigms, in practice our reliance on paradigms leads us 

to become increasingly reluctant to relinquish them even 

when faced with contradictory data. As a consequence, 

paradigms are more commonly applied than tested: what 

begins as hypothesis evolves into unalterable truth. This 

is in spite of the fact that the creators of new paradigms 

commonly are the most cautious in the extrapolation of 

their models and warn readers against indiscriminate 

application. The proponents of sequence stratigraphy, for 

example, urge us to use the concept as a "tool rather than 

a template" (H. Posementier, oral commun., 1989). 

With these caveats, why do we still have the 

tendency to apply paradigms without questioning them? 

In large measure, this tendency stems from the need to 

interpret an increasingly bewildering amount of data 

from diverse specialties in which we have limited or no 

expertise and must rely on prevailing thought to narrow 

the number of possible interpretations. Also, the 

propensity of scientists to hold tenaciously to 

conventional wisdom is understandable in light of new 

knowledge of the partitioning of brain functions. The 

analytical and organizational left hemisphere of the brain 

seeks explanations for random information already in 

storage. Although this ordering is an important and 

necessary function, the left hemisphere becomes 

reluctant to give up a model that it sees as a satisfactory 

explanation for otherwise random information. With 

time, a paradigm can become deeply rooted and virtually 

ineradicable, even in the face of new data that may be 

contradictory to the paradigm. Moreover, paradigms 

stored in the left hemisphere filter new observations that 

enter the visual right hemisphere of the brain, a process 

that also hinders formulation of new concepts. In light of 

this inclination to override the implications of new 

observations, our objectivity as scientists is questionable. 

This coloring of our thought processes comes through in 

the humorous admission, "I would never have seen it if I 

hadn't believed it myself." 

In the study of sedimentary basins, the basin 

analysis approach forces rigorous testing of scientific 

paradigms because the multidisciplinary nature of the 

approach necessitates the integration of data from 

diverse specialties. Feedback from diverse specialties 

provides numerous constraints so that no conclusion can 

be drawn about one aspect of a basin's history without 

affecting the interpretation of other aspects. Thus, when 

a conclusion from one line of evidence is at variance with 
a conclusion drawn from several other lines of evidence, 

we must challenge the assumptions that led to the 

different conclusions-which usually involves examining 

cherished theories or paradigms. The reluctance to 

relinquish paradigms is more easily overcome when 

several lines of evidence point toward new concepts that 

have exciting implications of their own. Basin analysis, by 

its integrative nature, pushes us toward new perspectives 

and thus serves to promote new discoveries in geoscience. 

A case study in the San Juan Basin of New Mexico 

serves as an example of the basin analysis approach to a 

geologic problem. It also points out that answers to 

questions not initially posed can sometimes be the most 

significant (and surprising) outcome of a basin study. The 

original goal of the San Juan Basin study was to develop 

a genetic model for sandstone-type uranium deposits in 

the Jurassic Morrison Formation. Tectonic, geophysical, 

sedimentologic, petrographic, hydrologic, and geochemical studies were drawn together so that mineralization 

could be evaluated in the context of the entire 

depositional, structural, and diagenetic framework. The 

result was not only a model for uranium mineralization, 

but also, somewhat unexpectedly, the overturning of 

several paradigms and their replacement with new 

concepts. Many of these new developments were 

unrelated to the solution of the original problem. 

One new result of the San Juan Basin study is that 

it was possible to document that authigenic illitic mixedlayer clays in the Upper Jurassic Morrison Formation 

formed at near-surface conditions in the absence of 

elevated temperatures. This finding contrasts with the 

"Gulf Coast model" for illite formation, in which 

temperatures of at least 90 oc are thought to be required. 

The "Gulf Coast model," in which composition of 

illite/smectite mixed-layer clays is attributed to increasing 

temperatures attendant with increasing burial, had 

become a paradigm throughout the petroleum industry. 

In the San Juan Basin study, because the basin analysis 

approach was used, formation of authigenic illite was not 

viewed as an isolated event. The process instead was 

constrained by other lines of evidence, including 

inferences from associations with other authigenic 

minerals; vitrinite reflectance data; petrographic 

constraints; paragenetic relationships; reconstructions of 

burial and thermal history; and hydrogeochemistry. 

Thus, the "Gulf Coast" paradigm, requiring elevated 

temperatures, did not provide a valid model for illite 

formation in this study. It became apparent that, in 

certain instances, pore-water chemistry alone can 

facilitate formation of authigenic illite, and thus that illite 

is not always a reliable geothermometer. Therefore, the 

"Gulf Coast model" offers one, but not the only, 

mechanism by which authigenic illite can form. This 

example serves to illustrate that a paradigm cannot be 

83 

generalized to include all cases. The paradigm was 

correct, yet did not provide a unique solution to the 

problem. In other cases, a paradigm is invalid because 

the underlying assumptions are incorrect. In either case, 

basin analysis provides internal checks on the validity of 

paradigms and highlights inconsistencies that would not 

be evident if only the constraints within individual subdisciplines were considered. 

R.K. Matthews stated in a letter to the editor of 

Geology in 1985, "A paradigm is the framework within 

which we attempt to solve problems," not necessarily the 

solution to the problem itself. The integrative nature of 

the basin analysis approach allows a synoptic rather than 

a myopic view of specific geologic problems, and the 

multidisciplinary nature of the approach forces us to 

scrutinize each paradigm because each paradigm has 

consequences for the whole, beyond the solution of an 

isolated problem. The approach can be applied to any 

geologic problem and will serve to advance science by 

continuing to lead us away from current paradigms, as 

multiple lines of evidence force us to question our most 

cherished beliefs. 

Depositional and Diagenetic Controls on 

the Residence and Isotopic Composition 

of Sulfur in Middle Pennsylvanian Coals, 

Southeast Iowa and Northwest Illinois 

Michele L. Tuttle, Cynthia A. Rice, 

Joseph R. Hatch, and Richard D. Harvey 

In the Midcontinent region from Kansas and 

Oklahoma eastward, Pennsylvanian high-sulfur coal is 

found in cyclothems. These alternating sedimentation 

cycles record the contest waged in the Pennsylvanian 

between the sea and the rivers: when sediment deposited 

by rivers exceeded basin subsidence, deltaic clay-rich 

sediment was deposited in channels and organic matter 

(precursor to the coal) accumulated in vast swampy 

lowlands. When subsidence exceeded infilling, the sea 

crept eastward, drowning the swamps and depositing 

marine shales and limestones. The rapidly alternating 

environment profoundly affected the sulfur geochemistry 

of the Pennsylvanian coal. The depositional and diagenetic conditions associated with these changes were 

investigated by studying various forms of sulfur and their 

isotopic composition in the Colchester No. 2 coal in the 

Carbondale Formation and associated deltaic and 

marine shale from three different locations. We also 

analyzed acid-soluble metals and organic carbon and 

calculated the degree of iron and organic-matter sulfidization. 

A 0.35-m coal seam in the Star Mine 12, Monroe 

County, Iowa, is overlain by two organic-rich, marine 
black shales (1.2 and 3.6 wt. percent S; o

34 SFeS2 =-24.3 

and -32.9%o, respectively). The coal contains abundant 

sulfur (5.4 wt. percent), half of which occurs as sulfide 

minerals. Sulfide minerals are FeS2 (o34S=-14.6%o) in 

the upper coal bench, and FeS2 (o34 S =-8.7%o) and ZnS 

(o34S=-16.9%o) in the basal coal bench. Organic S 

(o34S=-14.1%o) makes up 40 percent of the totalS and 

3.3 wt. percent of the organic matter. The 34S-depleted 

isotopic composition and high sulfur content of the 

organic matter indicate that the organic matter has been 

sulfidized by bacteriogenic H2S of similar isotopic 

composition to sulfur in sulfide minerals. The negative 

o34 S values indicate that an unlimited sulfate reservoir 

was available to the sulfate-reducing bacteria. All the 

iron in the basal coal is sulfidized; excess bacteriogenic 

sulfide (possibly associated with organic matter) was 

available in the basal unit to react with Zn in possible 

hydrothermal fluids moving through the coal, as noted in 

a 1988 study by J.F. Whelan and others. 

A 0.71-m coal seam in the Cedar Creek Pit 5, 

Schuyler County, Ill., is overlain by 2 m of gray deltaic 

shale (6.0 wt. percentS; o

34SFeS2 = + 10.9%o), 1.7 m of 

black marine shale, and 1 m of marine limestone. FeS2 

(o34 S = + 1.6%o) in the coal generally constitutes half of 

the total S (3.7 wt. percent); the other half is organicS 

(o34S = + 11.2%o) which constitutes 3.1 wt. percent of 

the organic matter. Similar o

34S values for the FeS2 and 

organic S and a high sulfur content of the organic matter 

indicate that the organic matter in the coal was sulfidized 

by bacteriogenic H2S. The positive o

34S values and sulfur 

content indicate that a large, but not unlimited sulfate 

reservoir was completely reduced by sulfate-reducing 

bacteria to H2S that sulfidized nearly all the iron in the 

coal; excess H2S sulfidized organic matter. 

A 0.49-m coal seam in the Cedar Creek Pit 3 is 

overlain by at least 7.6 m of gray deltaic shale (0.14 wt. 

percent S; o

34SFes2 = + 1.5%o ). FeS2 (o34S = + l4.6%o) 

in the coal makes up 20 percent of the total S (1.5 wt. 

percent), whereas organic S (o34S = + 13.9%o) 

constitutes 58 percent of the total S and only 0.6 percent 

of the organic matter. Less than half the iron in the coal 

is sulfidized. The low degree of iron sulfidization, low 

FeS2 content, and positive o

34SFes2 values indicate that a 

small sulfate reservoir was completely reduced by 

bacteria. The bacteriogenic H2S was consumed by 

reaction with iron, leaving little, if any, to sulfidize the 

organic matter, hence the low sulfur content in the 

organic matter. 

From these examples, the sulfur geochemistry in 

the Colchester No. 2 coal appears to have been 

controlled by the environment in which the overlying unit 

was deposited. Marine black shale overlying coal 

indicates that subsidence exceeded infilling and the 

swamp was flooded by seawater. Abundant seawater 

sulfate diffused into the swamp deposits, producing an 

unlimited sulfate reservoir for the sulfate-reducing 

84 

bacteria. Where the coal is overlain by a relatively thin 

unit of deltaic shale, which in turn is overlain by marine 

black shale, seawater sulfate diffused into the swamp 

deposits, producing a large, but not unlimited sulfate 

reservoir for the bacteria to reduce. Where the coal is 

overlain by a thick sequence of deltaic shale, the swamp 

deposits were isolated from seawater sulfate. FeS2 was 

formed when bacteria reduced the small freshwater 

sulfate reservoir in the swamp and the organic S was 

inherited from the sulfur assimilated in the growing 

vegetation. 

Depositional Processes Revealed by 

GLORIA Sidescan Sonar Images on the 

Mississippi Fan 

David C. Twichell, Neil H. Kenyon, and 

Bonnie A. McGregor 

GLORIA (Geologic LOng Range Inclined Asdic) 

sidescan sonar images have been used in combination 

with 3.5-kHz high-resolution subbottom profiles to infer 

the depositional processes that formed the surface of the 

Mississippi Fan. These images show that three distinct 

depositional stages occurred in the formation of the 

surface of the fan. The stages are represented in the 

images by regions of distinctive acoustic backscatter. A 

region of low backscatter rims the margin of the fan. The 

overlapping relationships seen on the 3.5-kHz profiles 

indicate that this region is the oldest of the three stages. 

The 3.5-kHz profiles and available core data suggest that 

this peripheral region consists of hemipelagic and turbidite deposits. 

The next oldest region of the fan is marked by 

linear high-backscatter stripes separated by areas of 

lower backscatter. These stripes are as much as 150 km 

long and as much as 10 km wide; they radiate 

southwestward from a large channel that originates in the 

Mississippi Canyon area and trends southeastward across 

the apex of the fan. The linear stripes apparently 

represent overbank flows that breached the levees of the 

main channel. The absence of channels coincident with 

the stripes suggests that these flows were largely nonchannelized. Their presence downslope from sections of 

the main channel that have been buried by younger 

sediments indicates an intermediate age between the 

deposits having the low-backscatter surface and those 

having a high-backscatter surface. 

The third, and youngest, backscatter region 

consists of a series of elongate, overlapping, lobe-shaped 

features. These lobes often exceed 200 km in length and 

75 km in width and can reach 40 m in thickness. They 

have high-backscatter surfaces and coincide with 
011 

Ill 

Upper /eft-Navajo Point from lake Powell, southeastern corner of Kaiparowits Plateau, southern Utah. Cliffs in foreground are eolian Navajo Sandstone. Top of plateau 

(approx. 3,800 ft above lake level) consists of stacked shoreface deposits of the John Henry Member of the Straight Cliffs Formation (Coniacian to early Campanian). 

Original color slide by Peter J. McCabe. Upper right-Straight Cliffs of Fiftymile Mountain, Kaiparowits Plateau, Utah, composed of coarsening-upward parasequences 

of the John Henry Member of the Straight Cliffs Formation. Major coal deposts in central part of plateau lie lateral to the vertically stacked shoreface deposits. Original 

color slide by Peter J. McCabe. Lower left-Cross section of a swilley in a coal of the Straight Cliffs Formation. Swilleys are interpreted to be the deposits of crevasse 

splays into mires. Note erosion of middle coal bed and thinning of upper coal bed over sandstone due to differential compaction. Original color slide by Keith W. Shanley. 

Lower right-Cedar Breaks National Monument, a scenic feature of the Cedar City 1 ox 2° area, southwestern Utah. Original color slide by L.M.H. Carter. 
acoustically transparent lenses on the 3.5-kHz subbottom 

profiles. The lobes either radiate from the end of the 

main channel or eastward from a sharp bend in the 

channel. A study of one lobe shows that it consists of a 

series of smaller elongate high-backscatter areas (5-40 

km in length) located at the ends of previously 

unrecognized small channels ( < 5 m deep). These small 

channels extend as much as 120 km from the main 

channel, and the high-backscatter areas at their ends are 

interpreted to be sites of deposition. Channelized turbidites or debris flows are the inferred process of 

deposition. 

The different backscatter patterns of the three 

regions and their relative age relationships suggest that 

different depositional processes were active at different 

times during the development of the present Mississippi 

Fan surface. The acoustic variability that is expressed in 

the GLORIA images on the surface of the fan suggests 

that laterally discontinuous and variable facies are 

present. This variability needs to be reconciled with the 

apparent uniformity of the facies inferred from lowfrequency seismic-reflection profiles across these areas 

of the fan. 

Chemical and Physical Characteristics of 

Coal Beds from the Salt Range Coal 

Field, Punjab Province, Pakistan 

P.O. Warwick, T. Shakoo'r, S. Javed, S.T.A. 

Mashhadi, and M.l. Ghaznavi 

From 1985 to 1988 forty-four coal samples were 

collected from the Patala Formation, Paleocene age, in 

the Salt Range coal field, a westerly-trending, 15 X 100 

km area, in Punjab Province, Pakistan. Five of these 

samples were collected from drill core, and the remaining 

39 were collected from channels cut in fresh coal faces in 

35 underground mines. Coal bed thicknesses from 37 

sample localities averaged 0.49 m, with std. dev. 

(standard deviation) 0.25. Results of proximate and 

ultimate analyses, reported here on an as-received basis, 

indicate that the coal beds have an average ash yield of 

24.23 percent with std. dev. 9.76, average sulfur content 

of 5.32 percent with std. dev. 2.52, average pyritic sulfur 

content of 4.07 percent with std. dev. 2.5, and average 

calorific value of 8,943 Btu with std. dev. 1,467. Eleven 

samples, analyzed on a whole-coal, dry basis for selected 

trace elements and oxides, have anomalously high 

average concentrations of Ti, at 0.36 percent; Zr, at 382 

ppm; and Se, at 11.4 ppm, compared to worldwide 

averages for these elements in coal. 

Correlation coefficients were calculated among 

trace-element, oxide, proximate, ultimate, location, and 

86 

coal-bed-thickness data. Sample localities were assigned 

to the eastern, central, and western parts of the coal field, 

which roughly correspond to areas of previously defined 

depositional facies of the coal-bearing strata: the coal 

beds in the western area are interbedded with deposits of 

a northerly-trending barrier-bar complex; the coal beds 

in the central part of the coal field are associated with 

lagoonal and tidal flat deposits; and coal beds in the 

eastern part of the coal field are associated with upper 

shore face and tidal channel deposits. 

Some positive correlations, significant at the 0.01 

level, are those between total sulfur and As, pyritic sulfur 

and As, total sulfur and location, organic sulfur and Se, 

calorific value (Btu) and location, and coal bed thickness 

and Se. In general, the thickest coal beds with the lowest 

total sulfur content are in the central part of the coal 

field. Organic sulfur and selenium contents are greatest 

in the eastern part of the coal field; pyritic sulfur content 

is greatest in the western part of the coal field. Total ash 

yields increase toward the east. Calorific values for the 

samples, calculated on a moist, mineral-matter-free 

basis, indicate that the rank of the coal is high-volatile C 

bituminous. 

Some of the variations observed in the chemical 

and physical characteristics of the Salt Range coal beds 

may be related to the different depositional environments 

of the coal-bearing strata. The increase of ash and 

selenium concentrations in a landward direction 

probably indicates less stable, more fluvially influenced 

environments of peat deposition than elsewhere. 

Increased pyritic sulfur concentrations near the barrierbar complex may be related to post-peat, pyrite-filled 

burrows commonly observed in the upper part of the coal 

bed. The thickest coal beds that have the lowest ash and 

sulfur contents and highest calorific values formed from 

peats deposited in back-barrier, tidal flat environments of 

the middle part of the coal field. 

Genesis and Distribution of Uraninite in 

Solution-Collapse Breccia Pipes, 

Northwestern Arizona 

Karen J. Wenrich, Bradley S. Van Gosen, and 

Hoyt B. Sutphin 

Thick sequences of karst-forming Mississippian 

limestone extend across the Colorado Plateau and into 

adjacent areas of the Basin and Range and Rocky 

Mountain region. As much as 800 ft of the Redwall 

Limestone, which underlies or caps the various high 

plateaus of the southwestern Colorado Plateau in 

Arizona (fig. 1 ), is responsible for one of the finest karst 

terranes in the United States. By the close of the 
3 

0 116 

e Breccia pipe with U production 

0 Breccia pipe with U mineralization 

Kingman 

• 

UTAH 

02 

Williams 

• 

0 Turn of the century breccia pipe Cu mine 

• Stratabound Cu prospect district 

Figure 1 (Wenrich). Map showing the location of U-rich breccia pipes, copper prospects, and the Apex mine (a Ga-Ge-rich 

breccia pipe). The lightly shaded area on the Colorado Plateau indicates terrane capped by the Mississippian Redwall 

Limestone or younger strata-rock necessary for the formation of solution-collapse breccia pipes containing uranium 

orebodies. The dark shading indicates the same terrane in the Basin and Range-areas that have potential for breccia pipes, 

but have not been explored for them. Breccia pipes discussed in the text are shown with the following numbers on the map: 

(1) Arizona 1, (2) Canyon, (3) EZ-1, (4) EZ-2, (5) Hack 1, (6) Hack 2, (7) Hack 3, (8) Kanab N, (9) Orphan, (10) Pigeon, and (11) 

Pine nut. Plateaus mentioned in the text are shown with the following letters on the map: (CP) Coconino Plateau, (HP) Hualapai 

Plateau, (KIP) Kaibab Plateau, (KP) Kanab Plateau, (MP) Marble Plateau, (SP) Sanup Plateau, and (SHP) Shivwits Plateau. 

Mississippian, extensive karst had formed in the Redwall-extensive enough to promote the formation of 

thousands of breccia pipes, typically 100-500 ft in 

diameter. The breccia pipes later propagated upward by 

stoping and collapse of as much as 3,000 ft of overlying 

Pennsylvanian and Permian sandstone, shale, and 

limestone. The karst provided channelways for removal 

of clisaggregated material by circulating waters that 

87 

dissolved the carbonate cement of the overlying strata 

and reactivated the Redwall karst. Breccia pipes were 

actively stoping upward during the Leonardian (about 

260-270 Ma), as shown by the thickening of the 

Harrisburg Member of the Lower Permian Kaibab 

Limestone over the Canyon breccia pipe (W.P. Casaclevall, oral presentation, AAPG Albuquerque meeting, 

1989). Pipes either continued to stope or were 
co 

co 

) 

KAOLINITE -'----- --- --

QUARTZ -- - - - --

BARITE 

ANHYDRITE 

CHALCEDONY 

DOLOMI TE CALCITE 

?-- ? 

<.'o"' 

o'-" 

"'~#"""" "r 

"''o"' o"" o'""""~~ <(. «-' ~ 

""~~c."'" ~'"' ~"':"'~«-~&' 

\~( 

"''0~ 

,,.,..«-~"" ( 

NICKELINE RAMMELSBERGITE 

MILLERITE 

GERSDORFFITE 

VAESITE 

SIEGENITE 

BRAVOITE 

PYRITE -

ARSENOPYRITE 

MARCASITE ~ 

SPHALERITE 

CHALCOPYRITE - - ----

TENNANTITE 

ENARGITE 

) 

GALENA~ 

) 

GYPSUM -'-

!from Anhydrite alteration) 

DOLOMITE 

) 

KAOLINITE -·-

QUARTZ 

CALCITE-?--- >--

MILLERITE -

SIEG.-

BRAV.-

PYR.-

MARC. -

SPHAL. -

CCP . -

TENN. -- LUZONITE --

LAUTITE 

ENAR. BORNITE 

CHALCOCITE 

DJURLEITE 

DIGENITE 

NUKUNDAMITE 

PYROBITUMEN -

URANINITE --­

HEMATITE 

TIME 

-, 

__ -:::_COVELLITE / 

GOETHITE--

JAROSITE--

GYPSUM--

ZIPPEITE --

TORBERNITE --

MALACHITE --

LIMONITE--

AZURITE--

Figure 2 (Wenrich). Paragenetic sequence for minerals in solution-collapse breccia pipes of the southwestern Colorado Plateau. Thickness of bar indicates relative 

mineral abundance. Arrows point to a mineral that is replacing the mineral located at the tail of the arrow. 
Figure 3 (Wenrich). Detrital quartz grain (01) rimmed by uraninite (U). Later silica deposition 

encased the uraninite with a quartz overgrowth (02). The quartz lies within a carbonate matrix (C). 

Transmitted light photomicrograph with crossed nicols. Long dimension of photo =0.4 mm. 

Figure 4 (Wenrich). Two stages of uraninite mineralization. The early uraninite (large 

grains around the outside, labeled U1) was fractured and then uraninite was again 

deposited in a more wormy, less massive habit (unfractured material in center of view, 

labeled U2). Reflected light photomicrograph. Long dimension of photo= 1.34 mm. 

reactivated during the Triassic, as beds of the Upper 

Triassic Chinle can be observed dipping concentrically 

into pipes on the Marble Plateau just east of the Grand 

Canyon. 

89 

The Redwall Limestone is an excellent aquifer, as 

are many of the overlying sandstone units. When the 

breccia pipes formed, they connected several of these 

aquifers whose waters probably used the breccia pipes as 
conduits, thus permitting waters from different aquifers 

to mix. This unique scenario included: (1) highly 

permeable well-developed passageways for large-scale 

fluid movement, (2) access to the breccia pipes by several 

aquifers that undoubtedly contained diverse water 

compositions, and (3) the development of this linking of 

the aquifers during a relatively short period of time 

following a long period of total confinement. These 

unique conditions were amenable to deposition of a large 

suite of elements (including U, Ag, As, Co, Cu, Mo, Ni, 

Pb, V, and Zn); as a result rich deposits of uraninite 

formed that contain an unusual and large assemblage of 

minerals (104 species-some of which are listed in fig. 2). 

Mining of breccia pipes began during the late 

1870's, at which time essentially all mining was for copper 

with minor production of Ag, Pb, and Zn. In 1951 

uranium was discovered at the existing copper prospect 

in the Orphan breccia pipe (fig. 1). Until 1975 the 

Orphan was the only known breccia pipe uranium 

deposit in northwestern Arizona. During the period 

1956-1969, the Orphan mine yielded 4.26 million pounds 

of U30s from ore with an average grade of 0.42 percent 

U30s (figures from 1986 study by W.L. Chenoweth). In 

addition to uranium, 6.68 million pounds of copper, 

107,000 ounces of silver, and 3,400 pounds ofV20 5 were 

recovered from the ore (figures from 1986 study by W.L. 

Chenoweth). Between 1975 and the close of the 1980's, 

exploration was intensive, and 19 deposits containing 

over 50 million pounds of U30s were recognized; 10 

million pounds were mined between 1980 and 1987 from 

ore with an average grade of 0.65 percent U30s (figures 

from 1987 report by I.W. Mathisen, Jr.) from the 5 (Hack 

1, Hack 2, Hack 3, Pigeon, arid Kanab N) of these 

deposits that were put into production since 1980. 

Another 46 pipes have been identified that contain > 1 ft 

of 0.01 percent U30s (data from 1989 study by Sutphin 

and Wenrich). Most of the breccia pipes presently known 

to contain uranium resources lie on the Kanab and 

Coconino Plateaus-the two areas where exploration has 

been most intensive. Many additional pipes are buried 

with no expression on the overlying plateau surface, and 

many parts of northwestern Arizona need equally 

intensive exploration and drilling; thus, the potential for 

discovery of additional uranium reserves is enormous. 

Unfortunately, with the 1980's slide of uranium prices, 

which by 1989 had reached the low prices of the late 

1960's, no new mines are expected to go into production 

in the near future. 

The 104 minerals that have been identified within 

the breccia pipes can be roughly divided into six 

depositional stages with some overlap during the 3-5th 

stages (fig. 2). Abundant sulfides of Fe, Cu, Co, Ni and 

As from stages 2-3 provided enough reductant to permit 

precipitation of high-grade uranium. Uraninite 

(U02)-the only primary uranium-bearing phase identi90 

fied-was precipitated (1) in minor vugs, (2) as rims 

around detrital quartz grains (fig. 3), and (3) within the 

coarsely crystalline calcite matrix of stage 1. The 

morphology of uraninite is variable, ranging from distinct 

spheres and clusters of spheres to botryoidal crusts, thin 

''wisps," and irregular patches that replace previous 

matrix material. Uranium -bearing material of lower 

reflectivity has been observed associated with uraninite; 

microprobe analyses indicate that this Ca-P-U-bearing 

material is not a discrete phase, but perhaps a finegrained mixture of uraninite and apatite. Two periods of 

uraninite mineralization have been observed (fig. 4)-all 

late stage, that is, after deposition of most sulfides: (1) 

massive uraninite, which may have been deposited in two 

separate events prior to a major fracturing event within 

the pipes, and (2) a post-fracturing, wormy, finer grained 

uraninite. A large set of U-Pb isotopic analyses from the 

Hack 2, Hack 3, Pigeon, Kanab North, EZ-1, EZ-2, 

Arizona 1, Pinenut, and Canyon pipe orebodies shows 

that the main uranium-mineralizing event occurred 

roughly 200 Ma, that is, Early Jurassic; data from the 

Canyon and Pinenut pipes, however, indicate at least one 

earlier period of mineralization roughly at 260 Ma, Early 

Permian (data from 1988 study by K.R. Ludwig and K.R. 

Simmons). Whether or not these two isotopic ages 

correspond to the two stages of uraninite mineralization 

has not been determined. 

Although most of the primary ore minerals in the 

breccia pipes were deposited prior to the uraninite, some 

pyrite, sphalerite, and galena formed contemporaneous 

with, or after, the uraninite. In addition, pyrobitumen was 

deposited after the uraninite; in the more southern 

breccia pipes so was a sequence of the copper sulfides: 

bornite, chalcocite, djurleite, digenite, and covellite. 

Fluid inclusions within sphalerite, calcite, and dolomite 

indicate that ore-forming fluids had temperatures in the 

range of 80°C to 173°C, with salinities consistently > 9 wt. 

percent NaCI equivalent and most commonly > 18 wt. 

percent NaCl equivalent. Little quartz precipitation 

accompanied breccia pipe mineralization, except for latestage silica deposition as quartz overgrowths on detrital 

quartz grains; this quartz clearly follows uraninite 

deposition because the quartz overgrowths surround 

uraninite rims that enclose detrital quartz grains (fig. 4 ). 

Apparently, an earlier period of quartz instability 

occurred, presumably associated with deposition of the 

early uraninite-detrital quartz grains associated with 

some uraninite deposition are corroded. In addition, 

strong evidence exists that within breccia pipes the silica 

cement of the Coconino Sandstone was totally removed, 

causing the Coconino to settle downward into the pipe as 

loose sand (Vivian Gornitz, written commun., 1987; N.A. 

Brown, oral presentation, AAPG Albuquerque meeting, 

1989). 
Understanding the genesis of such high-grade 

sedimentary uranium deposits lies in recognizing the 

significance of the aquifer systems and the high 

permeability of the breccia pipes themselves, rather than 

in debating the age-old question of "source rock." 

Whether the ground water transporting the uranium 

carried 0.1 ppb or 10 ppb uranium is insignificant 

compared to the importance of the volume of water that 

was apparently flushed through the Paleozoic aquifers 

and breccia pipe conduits, and its interaction with the 

large mass of sulfides already residing in the pipes. This 

interaction would have reduced and precipitated the 

uranium from the ground water. 

The stability of the Colorado Plateau, perhaps 

aided by the reducing pyrite cap over most of the 

orebodies, preserved the high-grade uranium since its 

deposition 200 Ma. Canyon dissection, which probably 

occurred throughout the past 5 m.y ., has subjected many 

breccia pipes on the well-dissected Shivwits, Sanup, and 

Hualapai Plateaus to extensive erosion that permitted 

oxidation of their orebodies and formation of colorful 

supergene minerals (stage 6-fig. 2). The relatively 

undissected Kaibab, Kanab, Coconino, and Marble 

Plateaus undoubtedly contain most of the remaining 

breccia pipe uranium resources. 

The Point Lookout Sandstone-Changing 

Formation Architecture from 

Strandplain to Delta 

Robert S. Zech and Robyn Wright-Dunbar 

Throughout most of the San Juan Basin, New 

Mexico and Colorado, the Upper Cretaceous Point 

91 

Lookout Sandstone generally fits a cyclic shoreface 

model in which the dominant architectural element is a 

prograding linear strandplain lithosome. This is best 

shown in the Cortez, Colorado area (the Cortez strandplain), where repetitive lithologic units that accumulated 

in beach to inner-shelf environments record multiple 

transgressive-regressive cycles. (See fig. 1, p. 92.) 

Deposits from about five of these cycles are locally 

grouped into bundles that extend at least 20 km along 

depositional strike and change basinward over 17-20 km 

from foreshore sandstone to offshore mudrock of the 

time-equivalent Mancos Shale. Where the bundles of 

well-sorted shoreface sandstone are stacked, the 

formation thickens and forms excellent hydrocarbon 

reservoirs. 

The depositional setting changed in the vicinity of 

Durango, Colorado. There, deposits of a fluvialdominated delta-front and associated large distributary 

channels make up the Point Lookout Sandstone and 

overlying Menefee Formation (the Durango delta). Lenticular sandstone units, pervasive mudrock interbeds, 

and local slump features are common in the deltaic 

strata. Abundant current ripples in the distal delta-front 

deposits indicate northeast-flowing (offshore) and 

southeast -flowing (longshore) paleocurrents. Proposed 

subsurface models for the Durango area must include 

the alignment of local distributary axes, delta-mouth bars 

(strike-aligned reservoir discontinuity), and possible 

sandy clastic shelf plumes originating from the delta. 

Continuing research will focus on the transitional area 

between the strandplain and the delta, on deltasandstone geometry, and on reservoir 

compartmentalization, which will be directly applicable 

to the Ignacio-Blanco field. 
CD 

N 

WEST 

~ 

..J.L __ ~TRIB-<F -- UTARY 

- 0 .. ~~ .. \, :::JL 

v-

~" .. ,~ ~ 

I 

1 2 3 

--* ...:L_ 

-* DELTA PLAIN 

'-----

? 

15M LOFt 

6MI 

0 

10Km 

I I 

4 5 6 

EAST 

Figure 1 (Zech). Cross section from the Cortez area (west) to the Durango area (east) showing depositional environments of Point Lookout Sandstone. Vertical lines 

and numbers indicate locations of measured (outcrop) sections. 
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Reston 

Reston 

Reston 

U.S. Geological Survey 

Quissett Campus, Building B 

Woods Hole, MA 02543 
AUTHOR INDEX 

A 

Affolter, R.H., USGS, Denver.............................................................................................................................................................. 1 

Agee, W.N., Department of Geological Sciences, University of Texas at Austin, Austin, TX 78713 .................................. 46 

Agena, Warren, USGS, Denver ......................................................................................................................................................... 62 

Allard, DJ., Graduate School of Oceanography, University of Rhode Island, Narragansett, RI 02882 ............................... 3 

Anders, D.E., USGS, Denver....................................................................................................................................................... 2, 52 

Anderson, R.E., USGS, Denver ......................................................................................................................................................... 34 

Anderson, R.R., Geological Survey Bureau, Iowa Department of Natural Resources, Iowa City, IA 52242..................... 61 

Arthur, M.A., Graduate School of Oceanography, University of Rhode Island, Narragansett, RI 02882 ............................ 3 

Austin, J.A., University of Texas, Institute for Geophysics, Austin, TX .................................................................................... 24 

B 

Baird, J.K., USGS, Denver ........................................................................................................................................................... 27, 55 

Balay, R.H., USGS, Denver................................................................................................................................................................ 18 

Ball, M.M., USGS, Denver............................................................................................................................................................. 3, 81 

Barker, C.E., USGS, Denver ........................................................................................................................................................ 4, 5, 6 

Barton, C.C., USGS, Denver ................................................................................................................................................................ 6 

Bates, A.L. USGS, Reston.................................................................................................................................................................. 77 

Beyer, L.A., USGS, Menlo Park.......................................................................................................................................................... 9 

Bird, KJ., USGS, Menlo Park ................................................................................................................................................. 9, 16,30 

Bohannon, R.G., USGS, Menlo Park ................................................................................................................................................ 34 

Bostick, Neely, USGS, Denver........................................................................................................................................................... 10 

Bragg, L.J., USGS, Reston .................................................................................................................................................................. 14 

Brouwers, E.M., USGS, Denver ......................................................................................................................................................... 30 

Bruns, T.R., USGS, Menlo Park ................................................................................................................................................... 9, 11 

Bryant, Bruce, USGS, Denver............................................................................................................................................................ 40 

Burruss, R.C., USGS, Denver........................................................................................................................................................... 12 

c 

Campbell, E.V.M., Virginia Division of Mineral Resources, Natural Resources Bldg., P.O.B. 3667, 

Charlottesville, VA 22903 ............................................................................................................................. .......................... 13 

Carlson, P.R., USGS, Menlo Park .................................................................................................................................................... 11 

Carter, M.D., USGS, Reston ........................................................................................................................................................ 13, 14 

Carter, Virginia, USGS, Reston......................................................................................................................................................... 69 

Cercone, K.R., Department of Geoscience, Indiana University of Pennsylvania, Indiana, PA 15705 .................................. 12 

Collett, T.S., USGS, Menlo Park .......................................................................................................................................... 14, 16, 44 

Comer, V J ., USGS, Reston ................................................................................................................................................................ 77 

Cook, H.E., USGS, Menlo Park......................................................................................................................................................... 17 

Crovelli, R.A., USGS, Denver............................................................................................................................................................ 18 

Crowley, S.S., USGS, Reston ....................................................................................................................................................... 19, 79 

Crysdale, B.L., USGS, Denver............................................................................................................................................................ 5 

D 

D'Agostino, J.P., USGS, Reston ........................................................................................................................................................ 69 

Dean, W.E., USGS, Denver ........................................................................................................................................................... 3, 21 

Dickinson, K.A., USGS, Denver........................................................................................................................................................ 23 

Dillon, W.P., USGS, Woods Hole ............................................................................................................................................... 24, 81 

Dobson, Maxwell, Institute of Earth Studies, University College of Wales, Aberystwyth, Wales, U.K. .............................. 11 

Drew, L.J., USGS, Reston ................................................................................................................................................................... 26 

Dubiel, R.F., USGS, Denver ............................................................................................................................................................... 40 

Dyman, T.S., USGS, Denver............................................................................................................................................................... 27 

Dyni, J .R., USGS, Denver................................................................................................................................................................. 28 

95 
E 

Edgar, N.T., USGS, Reston ................................................................................................................................................................ 24 

Ethridge, F.G., Colorado State University, Fort Collins, CO ....................................................................................................... 31 

F 

Fannin, N.G.T., British Geological Sutvey, Edinburgh, Scotland ................................................................................................ 11 

Fanning, D.S., Department of Agronomy, University of Maryland, College Park, Md ........................................................... 69 

Fassett, J.E., USGS, Denver ............................................................................................................................................................... 28 

Fedorko, Nick, III, West Virginia Geologic and Economic Sutvey, Mount Chateau Resch. Ctr., 

P.O.B. 879, Morgantown, WV 26507-0879 ......................................................................................................................... 13 

Filewicz, M.V., Unocal Corporation, Ventura, CA ......................................................................................................................... 78 

Finch, W.I., USGS, Denver ................................................................................................................................................................. 29 

Finkelman, R.B., USGS, Reston ........................................................................................................................................................ 14 

Fisher, M.A., USGS, Menlo Park...................................................................................................................................................... 11 

Fishman, N.S., USGS, Denver............................................................................................................................................................ 82 

Foote, R.Q., Corpus Christi, TX 78411 .............................................................................................................................................. 3 

Fouch, T.D., USGS, Denver ........................................................................................................................................... 21, 30, 31, 40 

Franczyk, K.J., USGS, Denver ..................................................................................................................................................... 32, 40 

G 

Gamble, C.J., Huntley Meadows Park, Alexandria, Va ................................................................................................................. 69 

Gardner, J. V., USGS, Menlo Park .................................................................................................................................................... 21 

Gardner, N.K., USGS, Reston ............................................................................................................................................................ 13 

Gautier, D.L., USGS, Denver ............................................................................................................................................................. 33 

Ghaznavi, M.I., Geological Sutvey of Pakistan, Lahore ................................................................................................................ 86 

Ging, T.G., USGS, Denver .................................................................................................................................................................. 12 

Gluskoter, Hal, USGS, Reston.................................................................................................................................................... 10, 47 

Goldstein, R.H., University of Kansas, Lawrence, KS 66045 ......................................................................................................... 6 

Grauch, VJ.S., USGS, Denver ........................................................................................................................................................... 40 

Grout, M.A., USGS, Denver .............................................................................................................................................................. 40 

Grow, JA., USGS, Denver ........................................................................................................................................................... 34,71 

H 

Hait, M.H., Jr., USGS, Denver .......................................................................................................................................................... 52 

Hansley, P.L., USGS, Denver ............................................................................................................................................................. 23 

Hatvey, R.D., Illinois State Geological Sutvey, Champaign, IL 61820 ....................................................................................... 83 

Hatch, J.R., USGS, Denver ................................................................................................................................................................. 83 

Hatcher, P.G., The Pennsylvania State University, Fuel Science Program, 209 Academic Projects Bldg., 

University Park, PA 16802 .................................................................................................................................................... 77 

Hayes, T.S., USGS, Denver............................................................................................................................................................... 12 

Hester, T.C., USGS, Denver ........................................................................................................................................................ 34, 72 

Hettinger, R.D., USGS, Denver .................................................................................................................................................. 36, 51 

Higley, D.K., USGS, Denver ........................................................................................................................................................ 36, 37 

Holmes, C.W., USGS, Denver .......................................................................................................................................................... 37 

Howell, D.G., USGS, Menlo Park ..................................................................................................................................................... 38 

Huffman, A.C., Jr., USGS, Denver ................................................................................................................................................... 68 

Huggett, Quentin, Institute of Oceanographic Sciences, Wormley, England ............................................................................ 11 

Hutchinson, D.R., USGS, Woods Hole ..................................................................................................................................... 38, 42 

Isaacs, C.M., USGS, Menlo Park ....................................................................................................................................................... 39 

Islam, M.N., Geological Sutvey of Bangladesh, Dhaka ........................................................................................................... 10, 47 

J 

Javed, S., Geological Sutvey of Pakistan, Lahore ........................................................................................................................... 86 

Johnson, R.C., USGS, Denver .................................................................................................................................................... 40, 77 

Johnson, S.Y., USGS, Denver ............................................................................................................................................... 21, 40, 78 

Johnson, T.W., USGS, Reston ........................................................................................................................................................... 46 

96 
K 

Keighin, C.W., USGS, Denver ............................................................................................................................................................ 41 

Kenyon, N.H., USGS, Woods Hole ................................................................................................................................................... 84 

Khan, M.R., Geological Sutvey of Pakistan..................................................................................................................................... 81 

Khan, S.A., Geological Sutvey of Pakistan ....................................................................................................................................... 81 

King, J.D. USGS, Denver .................................................................................................................................................................. 39 

Kirschbaum, M.A., USGS, Denver ............................................................................................................................................. 42, 51 

Klitgord, K.D., USGS, Woods Hole .................................................................................................................................................. 42 

Krohn, KK, USGS, Reston ................................................................................................................................................................ 55 

Kvenvolden, KA., USGS, Menlo Park ............................................................................................................................................. 44 

Kyle, J.R., Department of Geological Sciences, University of Texas at Austin, Austin, TX 78713 ...................................... 46 

L 

Landis, E.R., USGS, Denver .............................................................................................................................................................. 47 

Law, B.E., USGS, Denver ...................................................................................................................................................... 49, 52, 77 

Lawton, T.F., New Mexico State University, Las Cruces, NM ..................................................................................................... 32 

Lee, M.W., USGS, Denver ................................................................................................................................................................ 81 

Lerch, H.E., USGS, Reston ................................................................................................................................................................ 59 

Lyons, P.C., USGS, Reston ................................................................................................................................................................. 61 

M 

Magoon, L.B., USGS, Menlo Park ................................................................................................................................................... 50 

Mann, D.M., USGS, Menlo Park ....................................................................................................................................................... 11 

Marincovich, Louie, Jr., USGS, Menlo Park ................................................................................................................................... 30 

Martin, Ray, Elf Aquitaine Petroleum, Houston, TX 77002 .......................................................................................................... 3 

Mashhadi, S.T.A., Geological Sutvey of Pakistan, Lahore............................................................................................................ 86 

Mason, M.A., University of California, Berkeley, CA ................................................................................................................... 78 

Mattick, R.E., USGS, Reston ............................................................................................................................................................. 51 

McCabe, P J., USGS, Denver ......................................................................................................................................... 36, 42, 51, 75 

McCammon, R.B., USGS, Reston ..................................................................................................................................................... 29 

McClellan, P.H., USGS, Menlo Park................................................................................................................................................... 9 

McGregor, B.A., USGS, Reston ........................................................................................................................................................ 84 

McKee, J.P., Department of Botany, Colorado State University, Fort Collins, Colo .............................................................. 70 

McNeil, D.H., Geological Sutvey of Canada, Calgary, Alberta .................................................................................................... 30 

M'Gonigle, J.W., USGS, Denver ........................................................................................................................................................ 52 

Michael, G.E., USGS, Denver ............................................................................................................................................................ 52 

Miller, B.M., USGS, Reston ............................................................................................................................................................... 53 

Miller, J.J., USGS, Denver .................................................................................................................................................................. 34 

Miller, W.G., USGS, Reston ............................................................................................................................................................... 55 

Molenaar, C.M., USGS, Denver .................................................................................................................................................. 40, 55 

Molnia, C.L., USGS, Denver .............................................................................................................................................................. 55 

N 

Nelson, C.H., USGS, Menlo Park ...................................................................................................................................................... 56 

Ness, G.E., Oregon State University, Cotvallis, OR...................................................................................................................... 24 

Neuzil, S.G., USGS, Reston ................................................................................................................................................................ 57 

Nichols, DJ., USGS, Denver .............................................................................................................................................................. 40 

Nichols, K.M., USGS, Denver ............................................................................................................................................................ 40 

Nielsen, D.T., USGS, Reston .............................................................................................................................................................. 27 

Nuccio, V.F., USGS, Denver ............................................................................................................................................................... 40 

0 

Obuch, R.C., USGS, Denver ............................................................................................................................................................... 27 

Obradovich, J.D., USGS, Denver ...................................................................................................................................................... 78 

Olhoeft, G.R., USGS, Reston ............................................................................................................................................................. 33 

Orem, W.H., USGS, Reston ............................................................................................................................................................... 59 

Ostwald, J., Broken Hill Proprietary Co., Wallsend, Australia .................................................................................................... 69 

Otton, J.K., USGS, Reston ........................................................................................................................................................... 29, 70 

Outerbridge, W.F., USGS, Reston ..................................................................................................................................................... 61 

Owen, D.E., USGS, Denver ................................................................................................................................................................ 70 

97 
p 

Palacas, J.G., USGS, Denver .............................................................................................................................................................. 61 

Parson, L.M., Institute of Oceanographic Sciences, Wormley, England.............................................................................. 11, 24 

Pedone, V.A., Department of Earth and Space Sciences, SUNY Stony Brook, Stony Brook, NY 11794 .......................... 12 

Perry, W.J., Jr., USGS, Denver ............................................................................................................................................. 40, 52, 62 

Peterson, Fred, USGS, Denver.................................................................................................................................................... 40, 63 

Peterson, J.A., USGS, Missoula, MT 59803 .................................................................................................................................... 64 

Pierce, B.S., USGS, Reston ................................................................................................................................................................. 64 

Pierson, C.T., USGS, Denver ............................................................................................................................................................. 29 

Pitman, J.K., USGS, Reston .................................................................................................................................................. 31, 32, 40 

Poag, C.W., USGS, Woods Hole ....................................................................................................................................................... 65 

Pollastro, R.M., USGS, Denver .......................................................................................................................................................... 39 

R 

Rahman, Q.M. Arifur, Geological Survey of Bangladesh, Dhaka ............................................................................................... 10 

Rice, C.A., USGS, Denver.................................................................................................................................................................. 83 

Rice, D.D., USGS, Denver .................................................................................................................................................................. 67 

Ridgley, J.L., USGS, Denver ........................................................................................................................................................ 67, 68 

Rieck, H., USGS, Flagstaff .................................................................................................................................................................. 30 

Robb, J.M., USGS, Woods Hole ....................................................................................................................................................... 72 

Robbins, E.l., USGS, Reston....................................................................................................................................................... 69, 70 

Robbins, S.L., USGS, Denver ............................................................................................................................................................. 71 

Ruppert, L.F., USGS, Reston ............................................................................................................................................................. 19 

Ryan, H.F., USGS, Menlo Park....................................................................................................................................................... 11 

s 

Sahl, H.L., USGS, Denver ................................................................................................................................................................... 34 

Sanchez, J.D., USGS, Denver ............................................................................................................................................................. 51 

Sawatzky, D., USGS, Denver .............................................................................................................................................................. 40 

Scanlon, K.M., USGS, Woods Hole .................................................................................................................................................. 24 

Schenk, C.J., USGS, Denver ........................................................................................................................................... 33, 41, 63, 71 

Schlee, J.S., USGS, Woods Hole ........................................................................................................................................................ 72 

Schmoker, J.W., USGS, Denver ............................................................................................................................................ 34, 61, 72 

Schouten, Hans, Woods Hole Oceanographic Institution, Woods Hole, MA 02543 ............................................................... 42 

Schuenemeyer, J.H., USGS and University of Delaware, Newark, DE 19711.. ........................................................................ 26 

Schumann, R.R., USGS, Denver ........................................................................................................................................................ 70 

Scott, R.W., Jr., USGS, Denver ......................................................................................................................................................... 40 

Sergeant, R.E., Kentucky Geological Survey, University of Kentucky, 228 Mining and Mineral 

Resources Building, Lexington, KY 40506-0107. ............................................................................................................... 13 

Shakoor, T., Geological Survey of Pakistan, Lahore...................................................................................................................... 86 

Shanks, W.C. III, USGS, Reston ....................................................................................................................................................... 46 

Shanley, K.W., USGS, Denver ..................................................................................................................................................... 51,75 

Shinn, E.A., USGS, Woods Hole ..................................................................................................................................................... 75 

Spencer, C. W., USGS, Denver ........................................................................................................................................................... 77 

Spiker, E.C., USGS, Reston ................................................................................................................................................................ 77 

Stanley, R.G., USGS, Menlo Park ..................................................................................................................................................... 78 

Stanton, R.W., USGS, Reston ............................................................................................................................................. 19, 64, 79 

Stevenson, A.J., USGS, Menlo Park ................................................................................................................................................. 11 

Stout, S.A., Union Oil of California, 376 S. Valencia Ave., Brea, CA ....................................................................................... 77 

Stricker, G.D., USGS, Denver ....................................................................................................................................................... 1, 79 

Suneson, N.H., Oklahoma Geological Survey, Energy Center, N-131, Norman, OK 73019 .................................................. 62 

Sutphin, H.B., USPCI, 5665 Flatiron Pkway, Boulder, CO 80301.. ...................................................................................... 29, 86 

Swift, B.A., USGS, Woods Hole ........................................................................................................................................................ 81 

Swisher, C.C., III, Berkeley Geochronology Center, Berkeley, CA ............................................................................................. 78 

Szantay, Adam, Colorado State University, Fort Collins, CO ...................................................................................................... 31 

98 
T 

Takahashi, K.I., USGS, Denver .......................................................................................................................................................... 37 

Taylor, M.E., USGS, Denver.............................................................................................................................................................. 17 

Tewalt, S.J., USGS, Reston .......................................................................................................................................................... 14, 55 

Thomas, R.E., USGS, Reston ............................................................................................................................................................. 81 

Thornton, M.L.C., Unocal Corporation, Ventura, CA .................................................................................................................. 78 

Triplehorn, D.M., Department of Geology and Geophysics, University of Alaska, Fairbanks, AK 99775 ................... 19, 61 

Turner-Peterson, C.E., USGS, Denver ............................................................................................................................................. 82 

Tuttle, M.L., USGS, Denver .................................................................................................................................................. 40, 78, 83 

Twichell, D.C., USGS, Woods Hole .................................................................................................................................................. 84 

v 

Van Gosen, B.S., USGS, Denver ....................................................................................................................................................... 86 

Van Hoven, R.L., USGS, Reston ....................................................................................................................................................... 69 

Verbeek, E.R., USGS, Denver ........................................................................................................................................................... 40 

Vork, D.R., Unocal Corporation, Ventura, CA .............................................................................................................................. 78 

w 

Wanty, R.B., USGS, Denver ............................................................................................................................................................... 40 

Watwick, P.D., USGS, Reston ..................................................................................................................................................... 79, 86 

Wenrich, KJ., USGS, Denver ...................................................................................................................................................... 29, 86 

Wesley, J.B., USGS, Denver ............................................................................................................................................................... 31 

White, R.S., University of Cambridge, Cambridge, U.K. CB30EZ ............................................................................................. 38 

Williams, C.F., USGS, Menlo Park .................................................................................................................................................... 39 

Wise, R.A., USGS, Denver ................................................................................................................................................................. 27 

Wright-Dunbar, Robyn, USGS, Denver........................................................................................................................................... 91 

y 

Young, G.K., GKY and Associates, Springfield, Va ...................................................................................................................... 69 

z 

Zech, R.S., USGS, Denver.................................................................................................................................................................. 91 

Zielinski, R.A., USGS, Denver ........................................................................................................................................................... 70 

Zihlman, F.N., USGS, Denver ............................................................................................................................................................ 51 

99 

i:< U.S. GOVERNMENT PRINTING OFFICE: 1989-773-047/06,029 REGION NO.8