USGS Research on Energy Resources-198tl 

Program and Abstracts 

V.E. McKelvey Forum on 

Mineral and Energy Resources 

U.S. GEOLOGICAL SURVEY CIRCULAR 1025 
Cover.-Scanning electron microscope photograph of authigenic albite and illitic 

mixed-layer clay (fibrous material) from saline, alkaline playa-lake deposits in the 

Brushy Basin Member of the Morrison Formation, near Durango, Colorado. The 

albite, present as a large overgrowth on a detrital feldspar, typically envelops the 

earlier formed illitic clay. Both authigenic albite and illitic mixed-layer clay have 

previously been used as geothermometers to assess the thermal history of potential 

hydrocarbon-bearing sequences; however, petrographic and geologic evidence 

suggests that pore-water chemistry alone, in the absence of elevated temperatures, 

controlled formation of these two minerals in the lacustrine units of the Brushy Basin 

Member. Photo by Neil S. Fishman; field of view is approximately 15 micrometers 

across. 

Title page.-Commercial value of coal is determined to a large extent by 

circumstances of peat deposition and by conditions of diagenesis in the peat stage. In 

the process of degrading plant material, bacteria may produce a relatively high 

content of undesirable iron sulfides-the bright pyrite clumps (framboids) in this 

photo-which decrease coal value. Degradation by fungi, on the other hand, may lead 

to formation of resistant fungal cysts (sclerotinite )-the symmetrical chambered 

bodies. The thermally inert sclerotinite contributes to good strength and high coal 

value if the coal is used to make metallurgical coke. The layered gray matrix in this 

Eocene coal from California is highly degraded wood products mixed with plant 

microspores (faint dark flecks). Photo by Neely Bostick; field approximately 

0.15 X 0.22 mm, polished surface, water immersion optics. 
United States Department of the Interior 

Geological Survey 

Reston, VA 22092 

Dear Reader: 

11inerals Management Service 

\Vashington, D.C. 20240 

February 26; 1988 

The U.S. Geological Survey (USGS) and Minerals Management Service (MMS) are 

nearing completion of a 2-year effort to assess the undiscovered oil and gas 

resources of the Nation. This investigation utilizes methodologies, 

assumptions, and data sets that are different than those used in previous 

assessments by the Department of the Interior~ 

This year's McKelvey Forum affords us the opportunity in the paper to be 

presented by Richard Mast to discuss our new approach to the difficult task 

of assessing undiscovered resources, and to present the preliminary basin 

results. 

In early April, the Department will release a working paper which will 

describe the details of the methodology, geologic, economic, and engineering 

assumptions, and preliminary petroleum basin assessments. The USGS and MMS 

will solicit formal and informal review of the methods and assumptions used in 

developing the working paper. The review process will include elements of the 

following: 

o Formal review by such organizations as National Academy of Sciences (Board 

on Mineral and Energy Resources), National Petroleum Council, and 

Association of American State Geologists. 

o Presentation of papers on methodology, assumptions, and results at meetings 

such as the McKelvey Forum and other professional conferences. 

o Regional workshops/conferences involving other Federal agencies,· States, 

industry, and interested organizations. 

Your views and opinions on the procedures, assumptions, and preliminary 

results presented in the working paper will be valuable in assisting the USGS 

and MMS in preparing a national assessment that would be widely understood and 

accepted as an accurate appraisal of this Nation's undiscovered oil and gas 

resources. 

Dallas L. Peck 

Sincerely yours, 

Director, Geological Survey 

td~:~~~) Director, Minerals ManagementService 


DEPARTMENT OF THE INTERIOR 

DONALD PAUL HODEL, Secretary 

U.S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director 

Organizing Committee for the 1988 McKelvey Forum: 

Donald L. Gautier, Chairman 

Mahlon M. Ball 

Lorna Carter 

Anny D. Coury 

Stephen L. Eittreim 

Joan J. Fitzpatrick 

Joseph R. Hatch 

Patricia Krupa 

Charles D. Masters 

Harry A. Tourtelot 

Katharine L. Varnes 

Library of Congress Cataloging in Publication Data 

V.E. McKelvey Forum on Mineral and Energy Resources 

(4th : 1988: Denver, Colo.) 

USGS research on energy resources-1988. 

(U.S. Geological Survey circular; 1025) 

Bibliography: p. · 

1. Power resources-Research-United States. I. Carter, Lorna 

M. II. Title. Ill. Series. 

TJ163.25.U6V23 1988 553.2'0973 87--600460 

Any use of trade names herein is for descriptive purposes only and does not imply 

endorsement by the U.S. Geological Survey. 

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

U.S. Geological Survey, Denver Federal Center, 

Box 25425, Denver, CO 80225 

1988 
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 

This volume contains summaries of lectures and posters included in the fourth 

V.E. McKelvey Forum on Mineral and Energy Resources, entitled "Roles of 

Geological Research in the Assessment of Energy Resources-1988." The McKelvey 

Forum serves as an opportunity for communication between the USGS and other 

earth scientists and users of the information, by presenting the results and progress of 

current USGS research as formal lectures. The informal poster sessions and more 

casual meetings provide an opportunity for concerned persons to meet individually 

with our scientists. I hope that the 1988 McKelvey Forum will help make our 

programs even more responsive to the needs of this community, particularly the 

fossil-energy industry, and that the interaction and cooperation begun here will 

continue and increase. 

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 which alternates between mineral and energy resources; this year the 

emphasis is on energy. Although the format and subject matter change somewhat 

from year to year, the primary purpose of the Forum remains the same: to encourage 

direct communication among USGS scientists, the representatives of other earthscience organizations, and interested individuals. 

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

geothermal sources, uranium-thorium, and oil shale. Our studies encompass the 

entire National domain, including the offshore Exclusive Economic Zone. The topics 

selected for this year's McKelvey Forum illustrate the breadth and depth of our 

research in energy resources. This year the program includes, among other subjects, 

(1) the results of the new joint MMS and USGS National assessment of undiscovered 

oil and gas in the United States; (2) new approaches to the application of organic 

geochemistry of petroleum source rocks, prediction of reservoir quality, and the 

entrapment of petroleum; (3) recent investigations of selected sedimentary basins 

including the Anadarko, Powder River, and Santa Maria basins; (4) new studies of 

coal depositional environment and new methodologies for evaluating available coal 

resources; (5) resource studies of offshore regions such as central California and the 

South Pacific island nations; ( 6) structural studies of the Midcontinent rift system and 

the early Mesozoic rift basins of the eastern seaboard. 

I am excited about this continuing opportunity to illustrate and discuss our 

research with our colleagues in industry and academia; we welcome your suggestions 

for improving the McKelvey Forum. 

IV 
V.E. McKELVEY FORUM-PROGRAM OF LECTURES AND 

DISCUSSIONS 

DENVER, COLORADO, FEBRUARY 29, MARCH 1-2, 1988 

Monday, February 29, 1988 

4:00p.m. 

5:00- 7:30 p.m. 

Tuesday, March 1, 1988 

8:30a.m. 

8:50 

9:30 

9:30 

10:00 

10:30 

11:00 

11:30 

12:00 

12:00 

1:45 p.m. 

1:45 

2:30 

3:00 

3:30 

Registration, Radisson Hotel 

Ice-breaker/Cash bar mixer 

Opening Session (Grand Ballroom, Radisson Hotel): Welcome and 

introduct01y remarks - Gary W. Hill, Dallas L. Peck, Benjamin A. 

Morgan 

Keynote Lecture - David A. White 

-Technical Session 1, Richard F. Mast, presiding 

Estimates of undiscovered oil. and gas resources for the onshore and 

State offshore areas of the United States Richard F. Mast, 

G.L. Dolton, R.A. Crovelli, RB. Powers, RR. Charpentier, D.H. Root, 

and E.D. Attanasi 

Coffee Break 

A rationale for the method of estimating the number of small 

undiscovered oil and gas fields L.J. Drew, J.H. Schuenemeyer, 

and E.D. Attanasi 

U.S. energy supply from the perspective of world petroleum geology 

Charles D. Masters 

The petroleum system-A classification scheme for research and 

resource assessment Leslie B. Magoon 

Adjournment of technical session; luncheon 

McKelvey Forum Luncheon, address by Norman H. Foster 

-Technical Session 2 (Grand Ballroom) 

Harold J. Gluskoter, presiding 

Coastal Sumatra-A modern analog for the ongm of Lower 

Pennsylvanian coal-bearing strata in the Eastern United States 

C. Blaine Ceci~ Sandra G. Neuzi~ and others (all authors listed with 

printed abstracts by first authors Cecil and Neuzil) 

Effects of climate, tectonism, and variations in sea level on the 

formation of the Cretaceous coals of North America Peter J. 

McCabe, Michael E. Brownfield, Dan E. Hansen, Roben D. Hettinger, 

Mark A. Kirschbaum, and J. David Sanchez 

Analcime in coal beds of the Wasatch Plateau, Utah-Geological and 

technological significance Roben B. Finkelman 

Available coal resources-A pilot study Jane R Eggleston, M. Devereux 

Ca11er, and James C. Cobb 

v 
PROGRAM OF LECTURES AND DISCUSSIONS (CONTINUED) 

4:00 

4:30 

5:00 

Identification and importance of coal bed gas, San Juan Basin, 

southwestern Colorado and northwestern New Mexico Dudley D. 

Rice, Charles N. Threlkeld, and April K Vuletich 

Abnormally high- and low-pressured oil and gas resetvoirs-Examples 

from Rocky Mountain region Charles W. Spencer 

Adjournment 

Tuesday evening, March 1, 1988 

7:30--10:30 p.m. 

Wednesday, March 2, 1988 

8:00a.m 

8:00 

8:30 

9:00 

9:30 

10:00 

10:30 

11:00 

11:30 

12:00 

1:30 p.m. 

1:30 p.m. 

-Technical Session 3: 63 poster papers, with authors and kegs on tap 

-Technical Session 4 (Grand Ballroom) 

D.L. Gautier, presiding 

Inorganic and organic geochemical cycles in petroleum source rocks of 

the Cretaceous Western Interior seaway-Records of 

paleoceanographic change Walter E. Dean, Michael A. Atthur, and 

Lisa M Pratt 

Paleoenvironmental and source rock assessment of black shales of 

Pennsylvanian age, Powder River and northern Denver basins J. L. 

Clayton, J.D. King, C.M Lubeck, J.S. Leventhal, and T A. Daws 

Potential petroleum source rocks in the Late Proterozoic Chuar Group, 

Grand Canyon, Arizona Mitchell W. Reynolds, James G. Palacas, and 

Donald P. Elston 

Petroleum geology of the northern part of the Arctic National Wildlife 

Refuge, northeastern Alaska Kenneth J. Bird, Leslie B. Magoon, and 

C.M Molenaar 

Coffee Break 

Dependence of sandstone porosity upon thermal maturity-An 

approach to prediction and interbasinal comparison of porosity 

James W. Schmoker and Donald L. Gautier 

Diagenetic evolution of deep hydrocarbon-bearing rocks in the 

Ordovician Simpson Group, Anadarko basin, Oklahoma- Evidence 

from mineralogic, stable isotope, and fluid inclusion studies 

Janet K Pitman and Robett C. Bunuss 

Low-temperature formation of illite-Implications for clay 

geothermometry and hydrocarbon generation Christine E. 

Turner-Peterson, Neil S. Fishman, and Douglass E. Owen 

Adjournment of Technical Session 4 

-Technical Session 5 (Grand Ballroom) 

Robert B. Halley, presiding 

Offshore resource geology of selected South Pacific Island NationsThe USGS SOPAC program H. Gary Greene, Michael S. Marlow, 

David W. Schol~ and John G. Vedder 

VI 
PROGRAM OF LECTURES AND DISCUSSIONS (CONTINUED) 

2:00 

2:30 

3:00 

3:30 

4:00 

4:30 

Offshore resource geology of central California David S. McCulloch and 

Stephen D. Lewis 

Crustal structure and deep rift basins of the midcontinent rift systemResults from GLIMPCE deep seismic-reflection profiles J.C. 

Behrendt, A. G. Green, W.F. Cannon, D.R. Hutchinson, M. W. Lee, B. 

Milkereit, W.F. Agena, and C. Spencer 

Distribution and structure of early Mesozoic rift basins on the 

continental margin of the Eastern United States KD. Klitgord and 

D.R Hutchinson 

Laramide thrusting of the Bighorn Mountains onto the Powder River 

Basin near Buffalo, Wyoming JA. Grow, E.N. Hinrichs, J.J. Miller, 

M W. Lee, and S.L. Robbins 

Seismic stratigraphy of the Bekes basin, Southeastern Hungary Robert 

E. Mattick, Jtmos Rumpler, Antal Ujfalusy, Bela Szanyi, and Iren Nagy 

Conclusion of Forum 

VII 
V.E. McKELVEY FORUM-POSTER SESSIONS 

Atlantic and Pacific Marine Geology 

Interpretation of seafloor processes in the Gulf of Mexico using the GLORIA sidescan sonar system 

Bonnie A. McGregor and David C. Twichell 

Banks, reefs, deltas, and fans-Jurassic-Cretaceous transition in the Baltimore Canyon trough 

C. Wylie Poag. John S. Schlee, B. Ann Swift, Mahlon M Bal~ and Linda Sheetz 

GLORIA survey off the East Coast of the United States 

J.M. Robb, D. W. O'Leary, W.P. Dillon, P. Popenoe, EA. Winget, J.S. Schlee, D.C. Twichel~ P.C. 

Valentine, and K.M. Scanlon 

Offshore resource geology of the Western United States-A new continental margins volume 

David W. Schol~ Anhur Grantz, and John G. Vedder 

Submarine canyons of the Florida Escarpment, eastern Gulf of Mexico 

D.C. Twichell and L.M Parson 

GLORIA sonographic mosaics of the Bering Sea and the western Aleutian Arc and adjacent North Pacific 

EEZ-Scan Bering Sea and Aleutian Arc Groups 

Coal Geology-Coal Geochemistry 

Petrographic and chemical character of Tertiary coals in northern California 

Neely H. Bostick 

Characterization of coals in the lower part of the Williams Fork Formation, Twentymile Park District, 

eastern Yampa coal field, Routt County, Colorado 

Michael E. Brownfield and Ronald H. Affolter 

Correlation of facies using chemical and maceral data in the C coal bed, Emery Coal Field, Utah 

Sharon S. Crowley and Ronald W. Stanton 

Basin evolution and upper Paleozoic coal deposits in the central Appalachian basin 

Kenneth J. Englund and Roger E. Thomas 

Organic geochemical studies of the early coalification of peat and associated xylem tissue 

Patrick G. Hatcher, Hany E. Lerch, Ill, T.V. Verheyen, and MA. Wilson 

Supergene enrichment of sulfur in coal deposits of the Powder River Basin 

Charles W. Holmes and Anthony B. Gibbons 

Implications of trace-element concentrations in modem tree fern tissues for the origin of elements in 

vitrinites of the Pittsburgh coal bed 

Paul C. Lyons and Cunis A. Palmer 

The distribution of rare-earth elements in the Pittsburgh coal bed 

James S. Mee, Cunis A. Palmer, and Charles L. Oman 

VIII 
POSTER SESSIONS (CONTINUED) 

The Campbell Creek/No. 2 Gas/Peerless/Powellton coal bed correlation from the middle part of the 

Kanawha Formation of the central Appalachian basin 

J.T. O'Connor 

Selenium in coal from the Powder River Basin, Wyoming and Montana 

C.L. Oman, R.B. Finkelman, S.L. Coleman, and LJ. Bragg 

The association of uranium with organic matter in a uranium-rich peat bog in the Carson Range near Lake 

Tahoe, Nevada 

W.H. Orem, RA. Zielinski, and J.K Otton 

Trace-element analysis of vitrinite concentrates- New approach for determining organic and inorganic 

affinity 

Cunis A. Palmer, Paul C. Lyons, and Janet D. Fletcher 

Comparative quality of the Upper and Lower Freeport coal beds in the Appalachian basin 

Brenda S. Pierce and Ronald W. Stanton 

Preliminary facies analysis of the sequence of rocks below the upper Wyodak coal bed, Paleocene Fort 

Union Formation, southeastern Powder River Basin, Wyoming 

Frances Wahl Pierce and Edward A. Johnson 

Manganese binding by iron bacteria in wetlands-A potential analog for manganese-rich coal 

E.l. Robbins, E. W. de Vrind, Hans de Vrind, and W.C. Ghiorse 

Coal quality and distribution in Upper Cretaceous and Tertiary rocks, east-central North Slope, Alaska 

Stephen B. Robetts 

Pakistan-A coal geologists' paradigm 

S.P. Schweinfutth, MJ. Bergin, W.O. Fredericksen, R.T. Hildebrand, E.R. Landis, W.F. Outerbridge, 

J.F. SanFilipo, F.O. Simon, P. D. Warwick, and C. Wnuk 

Eocene lava and epigene mineralization alter Alaska's thickest known coal deposit 

Gary D. Stricker and Ronald H. Affolter 

Stratigraphy and facies analysis of Tertiary units, western Medicine Lodge Basin, Montana 

Jean N. Weaver 

Indigenous sources of fossil fuels, Sahel region of North Africa 

Jean N. Weaver, Marion J. Bergin, Michael E. Brownfield, and Edwin R. Landis 

Paleobotanical composition of some Pennsylvanian coal beds from the central Appalachian basin as an 

indication of paleoclimate 

Richard B. Winston and Ronald W. Stanton 

Petroleum Geology-Petroleum Geochemistry 

Tertiary igneous intrusions and renewed petroleum generation in the western Delaware Basin, Texas 

Charles E. Barker and Mark J. Pawlewicz 

Hydrocarbon distribution in the Cretaceous-Tertiary Sagavanirktok Formation, North Slope, Alaska 

T.S. Collett and K J. Bird 

IX 
POSTER SESSIONS (CONTINUED) 

Burial history reconstruction of the Lower Cretaceous J sandstone in the Wattenberg Field, Colorado, 

"hot spot" 

D.K Higley and D.L. Gautier 

Santa Maria Project, central California coast 

C.M. Isaacs and RG. Stanley 

Kinetic models of organic reactions applied to burial history of sedimentary basins 

J. David King 

Organic geochemical studies of the Eastern U.S. early Mesozoic Newark Basin- Phase Two 

RK Kotra 

The role of thermal history in the presetvation of oil at the south end of the Moxa arch, Utah and 

Wyoming-Implications for the oil potential in the southern Green River basin 

B.E. Law and J.L. Clayton 

Petroleum geology of the People's Republic of China 

KY. Lee and C.D. Masters 

Stratigraphic framework of the Pannonian sequence (Neogene), Bekes basin, southeast Hungary 

C.M. Molenaar, I. Revesz, I. Berczi, A. Kovacs, Gy. K Juhasz, I. Gajdos, and B. Szanyi 

Estimation of paleogeothermal gradients and their relationship to the timing of petroleum generation, 

Eagle basin, northwestern Colorado 

Vito F. Nuccio, Christopher J. Schenk, and Santuel Y. Johnson 

Reconnaissance of Colorado Front Range bogs for uranium and other elements 

Douglass E. Owen, R Randall Schumann, and !antes K Otton 

Applying aromatic steroids to determination of thermal maturity of biodegraded heavy oils, tar sands, and 

bitumens 

!antes G. Palacas, Donald E. Anders, and J. David King 

Thermal maturation of the eastern Anadarko basin, Oklahoma 

Mark J. Pawlewicz 

Relation of major sea-level fall and regional unconformity to hydrocarbon accumulations, Upper 

Cretaceous Turner Sandy Member of Carlile Shale, Black Hills uplift 

Dudley D. Rice and C. William, Keighin 

Sequential, time-slice paleogeography of northwest Borneo, Southeast Asia, as a basis for the delineation 

of oil and gas plays 

Keith Robinson 

A major Eocene suture in the southern Washington Cascades-Are hydrocarbon source rocks buried 

beneath volcanic flows? 

Dal Stanley, Bill Reran, and Carol Finn 

Tectonic history and petroleum potential of eastern Washington and Oregon 

Marilyn E. Tennyson and Judith Totman Panish 

X 
POSTER SESSIONS (CONTINUED} 

Geology and petroleum resources of the Barents-northern Kara Shelf, U.S.S.R. and Notway 

Gregory Ulmishek 

Petroleum Resource Assessment-Resource Potential 

Small field oil and gas resource estimation for the National Assessment 

E.D. Attanasi and D.H. Root 

Oil and gas potential of the continental margin, offshore Virginia 

KC. Bayer and RC. Milici 

Scientific studies relevant to the question of Antarctica's petroleum resource potential 

John C. Behrendt 

The use of basin classification and analog basins in petroleum resource assessment 

Mark W. Bultman 

An assessment of gas resou:::ces in low-permeability sandstones of the Upper Cretaceous Mesaverde 

Group, Piceance basin, Colorado 

Ronald C. Johnson, Robert A. Crovelli, Charles W. Spencer, and Richard F. Mast 

Assessment of gas contained in overpressured low-permeability reservoirs in the Greater Green River 

basin of Wyoming, Colorado, and Utah 

B.E. Law, C. W. Spencer, RA. Crovelli, RF. Mast, G.L. Dolton, RR Charpentier, and C.J. Wandrey 

Sedimentology-Clay Mineralogy 

Phosphorus burial in the deep sea during the past 125 million years 

James R Herring, Walter E. Dean, and Michael A. Anhur 

Sedimentology of and petroleum occurrence in the Lower Permian Schoolhouse Tongue of the Weber 

Sandstone, northwest Colorado 

Samuel Y. Johnson, Christopher J. Schenk, Donald E. Anders, and Michele L. Tuttle 

Basin analysis studies of Cambrian through Mississippian rocks, Powder River Basin, Wyoming and 

Montana 

David L. Macke 

Diagenetic transformations and phosphate mineral precipitation in marine lakes of the Palau Islands 

W.H. Orem, W.C. Burnett, W.B. Lyons, W. Landing, and P. Chin 

Relationship of clay-mineral diagenesis to temperature, age, and hydrocarbon generation-An example 

from the Anadarko basin, Oklahoma 

Richard M Pollastro and James W. Schmoker 

Sedimentology of the Permian upper part of the Minnelusa Formation near Beulah, Wyoming-Analog 

for subsurface facies in the Powder River Basin 

CJ. Schenk, J. W. Schmoker, I.E. Fox, and M W. Lee 

Diagenesis of sandstones in the Permian upper part of the Minnelusa Formation, West Mellott field, 

Powder River Basin, Wyoming 

C.J. Schenk, RM. Pollastro, and J. W. Schmoker 

XI 
POSTER SESSIONS (CONTINUED) 

Structural Geology-Geophysics 

The Midcontinent rift in the Lake Superior region-Structural interpretation from deep seismic reflection 

profiling 

W. F. Cannon, John Behrendt, and A. G. Green 

Active folding in the Hispaniola-Caicos Basin and tectonic control of sediment distribution pathways from 

the Hispaniola insular margin 

W.P. Dillon, K.M. Scanlon, N. T. Edgar, and L.M Parson 

Faulting and folding on the eastern flank of the Bighorn Mountains, Sheridan and Johnson Counties, 

Wyoming 

E. Neal Hinrichs 

Processing techniques for deep crustal marine multichannel reflection seismic data-Examples from the 

Great Lakes 

M. W. Lee, W.F. Agena, and D.R. Hutchinson 

Seismic reflection profiles across the eastern Bighorn Mountains between Buffalo and Story, Wyoming 

John l. Miller, Myung W. Lee, John A. Grow, E.N. Hinrichs, and S. L. Robbins 

Overthrusting in the northwestern San Juan Basin, New Mexico-A new interpretation of the Hogback 

monocline 

David l. Taylor and A. Cunis Huffman, Jr. 

Abbreviations and conversion factors 

bbo 

mcf 

n.m. 

tcf 

BOE 

COCORP 

DSDP 

EEZ 

GLORIA 

INAA 

Moho 

NACS 

NCRDS 

Til 

To convert 

miles 

kilometers 

feet 

meters 

oc 

op 

To 

kilometers 

miles 

meters 

feet 

op 

oc 

billions of barrels of oil 

thousand cubic feet 

nautical miles 

trillion cubic feet 

barrels of oil equivalent 

Consortium for Continental Reflection Profiling 

Deep Sea Drilling Project 

Exclusive Economic Zone 

Geologic LOng Range Inclined Asdic 

Instrumental neutron activation analysis 

Mohorovi~ic discontinuity 

North American Composite Shales 

National Coal Resource Data System 

Time Temperature Index (Lopatin 

Multiply 

1.6Xmiles 

0.62Xkilometers 

0.3048Xfeet 

3.25Xmeters 

9/5 C+32 

5!9 (F-32) 

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

USGS Research on Energy Resources-1988 

Program and Abstracts 

Edited by L. M. H. Carter 

Small Field Oil and 

Gas Resource Estimation for the 

National Assessment 

E.D. Attanasi and D.H. Root 

The latest U.S. National onshore oil and gas 

assessment prepared by the U.S. Geological Survey 

evaluates oil and gas at the play level for nearly all United 

States petroleum provinces. However, play analysis 

methods were restricted to fields of at least 1 million 

barrels of oil or 6 billion cubic feet of gas, for which there 

exists a relatively complete and accurate data set. 

Nonetheless, it was recognized that there were resources 

in fields smaller than these cut-offs, and estimates were 

made o( resources within five small field-size classes: 

31,500 to 62,500 barrels, 62,500 to 125,000 barrels, 

125,000 to 250,000 barrels, 250,000 to 500,000 barrels, 

and 500,000 to 1,000,000 barrels of oil, or the barrels of 

oil equivalent in cubic feet of gas. 

Although small fields are numerous, their data set 

is so incomplete and inaccurate that it was not practical 

to analyze their potential on a play basis. Instead, 

estimates were made for provinces. 

The main assumption was that for each province 

there is a ratio, R greater than 1, such that the ultimate 

number of fields occurring in each class was R times as 

many as in the next larger class. 

Estimates for the numbers of ultimately occurring 

fields in the classes larger than 1 million barrels of oil or 

6 billion cubic feet of gas were derived from the data for 

past discoveries and the play estimates of remaining 

resources. From these estimates of the ultimate numbers 

of large fields, an estimate for R was calculated for each 

province. The ratio was then used to determine the 

ultimate number of fields in the small classes. Data 

available for the number of discovered fields was 

1 

subtracted from the ultimate numbers to give the 

number of small undiscovered fields. 

In order to enhance the economic utility of these 

projections, the number representing the expected value 

of undiscovered small fields in each province was 

allocated to four depth intervals, each of 5,000 feet. For 

each province, this allocation to depth intervals was in the 

same proportion as that of the discovered and estimated 

1,000,000 to 5,000,000 barrel-of-oil-equivalent oil and 

gas fields. 

The amounts of oil and gas in the small 

undiscovered fields were calculated by multiplying the 

midpoint volume of each of the five classes of fields by 

the number of fields in the class. 

Tertiary Igneous Intrusions and 

Renewed Petroleum Generation in the 

Western Delaware Basin, Texas 

Charles E. Barker and Mark J. Pawlewicz 

Above-average paleogeothermal gradients in the 

western Delaware Basin, which are associated with 

numerous igneous intrusions and increased heat flow, 

have thermally matured rocks as young as Late Permian. 

Mean random vitrinite reflectance (Rm )-depth profiles of 

samples collected from boreholes throughout the 

Delaware Basin form two distinct groups. One group, 

with a 0.5 %Rm!km gradient, is from the eastern portion 

of the basin, and the other, with a 0.7 %Rmlkm gradient, 

is from the western portion. The difference between the 

two groups is attributed to Tertiary thermal events that 

increased heat flow and reheated the rocks of the western 

Delaware Basin after uplift and erosion. Reheating of the 

Magnolia Cowden-1 borehole has caused Rm to vary 
from 0.6 % at 60 m (200 ft) near the top of the 

Guadalupian (Late Permian) to 2.8% in Devonian rocks 

at 2,900 m (9,500 ft). 

Post-Mississippian tilting has produced a thicker, 

mostly uneroded sedimentary section in the eastern 

portion of the Delaware Basin. In the western part of the 

basin, this tilting caused uplift and erosion that exposed 

the Upper Permian section, prior to Cretaceous time. 

Ages of igneous intrusions in the western half of the 

Delaware Basin show that they were emplaced 40-30 

Ma, followed by Miocene to Holocene (23-0 Ma) basinand-range type block faulting and associated high heat 

flow. Iso-reflectance contours cut across formation 

contacts in the western Delaware Basin, indicating that 

this heating is post -tectonic-that is, it occurred after 

eastward tilting and erosion had reduced burial depth. 

The Rm data and burial history reconstruction indicate 

that oil was generated during near-maximum burial in 

Permian time, and that the area was reheated by 

increased heat flow in Tertiary time. Maximum 

temperatures computed from Rm -depth relationships 

suggest that paleogeothermal gradients exceeded 40 

°C/km (2.2 °F/100 ft) in Tertiary time. This reheating 

thermally matured rocks as young as Guadalupian in the 

western Delaware Basin and caused a second episode of 

petroleum generation. By this time, however, the Permian reservoir rocks and Ochoan evaporite seals had 

been partially to completely eroded. Consequently, it 

appears that this furt~~ -r maturation of the Permian 

source rocks occurred w;~en conditions for trapping the 

generated petroleum were poor. 

These data suggest that there is little potential for 

major petroleum discoveries in the western Delaware 

Basin. Further, this study reiterates that the petroleum 

potential of large areas can be assessed by simple 

geologic methods-thermal history reconstruction, and 

measurement of maturity of the sedimentary organic 

matter. 

Oil and Gas Potential of the 

Continental Margin, Offshore Virginia 

K.C. Bayer and R.C. Milici1 

The prime objective of this study was to evaluate 

the oil and gas potential of the Virginia outer continental 

margin using publicly available seismic common depth 

point (CDP) lines. This reconnaissance seismic survey of 

eight cross-shelf profiles and two profiles subparallel to 

1

Virginia Division of Mineral Resources, Charlottesville, VA 

22903. 

2 

the coastline, totalling 729 statute miles (1,176 km), 

covered a Virginia offshore area of approximately 15,000 

mi2 (24,000 km2). 

Four stratigraphic horizons (near top of Upper 

Cretaceous, near top of Lower Cretaceous, near top of 

Jurassic, and an acoustic "basement" reflector) were 

correlated with horizons in the COST B-2 well; their 

depths were calculated from the travel times, and isopach 

and structural contours were compiled from the depth 

values. Preliminary results from the Shell 93-1 well, 

drilled through Cenozoic and Mesozoic strata offshore of 

Virginia, and from wells adjacent to the Virginia study 

area indicate low source-rock quality and thermal 

immaturity, suggesting deposition in oxidizing, openshelf environments. 

On the continental shelf, the acoustic basement 

reflector is generally the most dominant, continuous 

signal on the seismic profiles, suggesting a relatively 

dense, thick sequence of rock. If this sequence is a seal 

for hydrocarbons below, then several areas offshore of 

Virginia may be suitable drilling targets. Offshore Mesozoic basins, for example, the Norfolk Basin, may contain 

oil, gas, or both. Mesozoic basins offshore may contain 

sandstones and shales with scattered carbonate beds in 

sequences analogous to those in onshore basins. If depth 

of burial was insufficient to generate oil or gas in 

commercial quantities, these basins may still provide 

reservoirs for hydrocarbons migrating from other areas. 

In some areas structural traps may be present in older 

rocks; in addition, numerous stratigraphic targets occur 

in the Virginia offshore area where lower Mesozoic rocks 

wedge out against impervious rock masses. 

If Middle to Upper Jurassic strata are potentially 

favorable for hydrocarbon generation, then the updip 

pinch-out of these rocks, approximately 18 mi (30 km) 

east of and parallel to the Virginia coast, may be a 

suitable target area. 

A variety of structural anomalies in Mesozoic and 

Cenozoic strata below the continental slope appear to be 

the most attractive targets for exploration at present. 

Deep structural anomalies, such as the paleo-shelf edge, 

involving rocks at or below the acoustic basement, are 

potential hydrocarbon traps. 

Evaluation and exploration of these structures will, 

however, require deep drilling to resolve the source bed 

and reservoir characteristics and possible migration 

pathways in their contained strata. The probability that 

the Virginia continental margin contains commercially 

recoverable quantities of oil and (or) gas is rated as fair 

(moderate) to poor (low). 
Scientific Studies Relevant to the 

Question of Antarctica's 

Petroleum Resource Potential 

John C. Behrendt 

No petroleum resources are known in Antarctica, 

and information is lacking to make reliable estimates of 

undiscovered resources. The Antarctic Treaty 

Consultative Parties are nearing completion on an 

Antarctic Minerals Regime; however, no economic 

exploitation is likely for several decades in the hostile 

Antarctic environment, even if prices return to the high 

levels of a few years ago. Only giant (about 70 million 

tons or 0.5 billion barrels) or more probably supergiant 

(about 700 million tons or 5 billion barrels) fields would 

be reasonable to consider as economic. 

The tectonic history of Antarctica subsequent to 

the Gondwanaland breakup suggests that West 

Antarctica is the most likely area to contain petroleum 

resources, although East Antarctica cannot be excluded. 

Probably only the continental margins will be exploitable 

with present or soon-to-be-developed technology 

because of the several-kilometer-thick moving grounded 

ice sheet covering the rest of Antarctica. Since 1976, a 

number of countries have accelerated geophysical 

research programs over the continental margin, which 

are providing significant resource assessment 

information. These data and sparse drilling and bottom 

geologic samples suggest the presence of several 

kilometers of unmetamorphosed sedimentary rock 

(possibly of Cretaceous and Cenozoic age) beneath the 

Ross, Weddell, and Bellingshausen margins of West 

Antarctica, and beneath the Amery Ice Shelf-Prydz Bay 

area and rift basins beneath the narrow continental 

margin in East Antarctica. Aeromagnetic data indicate 

significant thicknesses of nonmagnetic sedimentary rock 

in several basins beneath the grounded ice sheet in East 

and West Antarctica. Diatoms and other microfossils 

present in moraines in the Transantarctic Mountains 

suggest the presence of Late Neogene sediments in the 

basins beneath the East Antarctic ice sheet, despite the 

onset of continental glaciation in the Oligocene. 

Several Deep Sea Drilling Project (DSDP) holes 

into the Ross continental shelf have shown the presence 

of Tertiary marine and nonmarine sedimentary rocks as 

old as Oligocene overlying early Paleozoic basement. 

Shows of gas in the DSDP holes cannot be considered 

evidence of any hydrocarbon resources, but analyses of 

thermogenic hydrocarbons were reported from samples 

taken offshore of the northern Antarctic Peninsula. As 

present and future geophysical and geologic studies 

outline possible prospective areas, scientific studies are 

needed of hazards associated with geologic, 

3 

meteorological, and oceanographic conditions, as well as 

ecosystems that might be adversely affected were 

petroleum development to occur. Examples of geologic 

hazards identified in several offshore areas include active 

faults in the Ross Sea continental shelf, gas hydrate 

beneath the continental slope off Wilkes Land, and 

iceberg scour marks on the sea bottom observed in two 

areas at depths greater than 500 m. 

Crustal Structure and Deep Rift 

Basins of the Midcontinent Rift 

System-Results from GLIMPCE 

Deep Seismic-Reflection Profiles 

J.C. Behrendt, A.G. Green,1 W.F. Cannon, 

D.R. Hutchinson, M.W. Lee, B. Milkereit,1 

W.F. Agena, and C. Spencer1 

Interpretation of GLIMPCE seismic-reflection 

profiles crossing western, central, and eastern Lake 

Superior and the northern end of Lake Michigan 

indicates that the midcontinent rift system (MRS) of 

volcanic and interbedded post-volcanic sedimentary rock 

of Keweenawan age is extensive. The rift deposits 

beneath Lake Superior are thicker and extend to greater 

depths (at least 32 km) than elsewhere along the MRS 

and perhaps anywhere else in the world. The thick 

volcanic units that make up the bulk of the rift deposits 

are areally extensive and continuous for lengths as great 

as 70 km on individual profiles. Lower crustal reflections 

vary in strength, distribution, and continuity along the rift 

axis, perhaps indicating variable amounts of crustal 

extension and mafic underplating accompanying rift 

formation, as suggested by many modern rift 

environments. 

Times to Moho vary along strike from 11.5 to 14 

seconds (about 37-46 km) in the west to 17 s in the 

center (about 55 km) and 13 to 15 s (about 42-49 km) in 

the eastern end of Lake Superior. Moho is least well 

defined in the reflection data beneath northern Lake 

Superior, at the pronounced bend in the MRS, where 

crustal thickness is greatest and the lower crustal 

reflections are the most complex. The prerift crust is 

25-30 km thinner beneath the central rift than beneath 

its flanks, providing evidence for crustal extension by 

factors of about 3 to 4. 

Total crustal thickness, 37-56 km, is considerably 

greater than the thicknesses reported for Phanerozoic 

continental rifts, and differs also in being equal to or 

greater than that of the surrounding (presumably unextended) regions. The MRS deposits may have analogs 

1

Geological Sutvey of Canada, 1 Obsetvatory Crescent, Ottawa, 

Ontario KlA OE8. 
with thick wedges of volcanic and clastic rift deposits 

buried beneath modern passive continental margins and 

with volcanic wedges of seaward-dipping reflectors found 

at continent/ocean junctions. 

Petroleum Geology of the 

Northern Part of the 

Arctic National Wildlife Refuge, 

Northeastern Alaska 

Kenneth J. Bird, Leslie B. Magoon, and C.M. 

Molenaar 

The northern part of the Arctic National Wildlife 

Refuge and adjacent Native lands, an area between the 

Brooks Range and the Beaufort Sea encompassing about 

2.4 million acres, is judged to have the geologic characteristics of a major petroleum province. Except for the 

undeformed northwest quarter, the area is involved in an 

east-west- and northeast-trending, north-verging 

imbricate fold and thrust-fault system related to Brooks 

Range deformation. 

The most likely petroleum-reservoir rocks are 

sandstones of Cretaceous and Tertiary age and intrabasement carbonate rocks of pre-Mississippian age. 

Clastic and carbonate reservoir rocks of Mississippian to 

Triassic age, similar to the reservoir rocks at Prudhoe 

Bay, are truncated by Early Cretaceous erosion related 

to rifting; these rocks are expected to occur in the 

southern part of the area considered. 

Analyses of hydrocarbons from oil seeps and oilstained rocks in outcrop suggest that three types of oil are 

present, all dissimilar to oils from the Prudhoe Bay area. 

The most important source rock for oil is postulated to 

be the Tertiary(?) and Cretaceous Hue Shale. With a 

present-day geothermal gradient of about 30 °C/km (1.6 

°F/100 ft), oil generation is expected to occur between 

depths of 3.7 and 6.9 km (12,000-22,500 ft), mostly 

within the thick Cretaceous and Tertiary (Brookian) 

sequence. Oil generation, accompanied by clay-mineral 

transformation and abnormal-fluid-pressure development, probably began about 50 Ma at the southern edge 

of the coastal plain and progressed northward, reaching 

the coastline about 10 Ma. 

Seismic data indicate that many more structures 

are present than have been previously suspected. Shortwavelength folds, perhaps numbering in the hundreds, 

are complexly faulted and involve mostly Brookian rocks. 

These folds overlie one or more regionally extensive 

low-angle faults that structurally detach them from a 

relatively small number of long-wavelength, moderately 

faulted structures composed mostly of pre-Brookian 

4 

rocks. Structural traps are believed to have formed 

before, during, and after oil generation and migration. 

Mean value estimates of in-place oil and gas 

resources for a 1.5-million acre part of this area are 13.8 

billion bbl of oil (bbo) and 31.3 trillion fe of gas. The 

amount of economically recoverable oil in 26 seismically 

mapped structures in estimated at 3.2 bbo (mean value). 

Evaluation showed that natural-gas resources are not 

economically recoverable. 

Petrographic and Chemical Character of 

Tertiary Coals in Northern California 

Neely H. Bostick 

The only two significant coalfields in northern 

California are accessible today though their period of 

most active mining was from 1870 to 1900. Parts of the 

Mount Diablo field, 30 miles east of San Francisco, are 

open in a public park administered by mining engineers, 

and part of the lone field 60 miles farther east is exposed 

because the lignite has been worked anew since 1947 for 

montan wax. Minor coal occurrences outside these fields 

are accessible in outcrop. 

The Mount Diablo subbituminous and the lone 

lignitic coals lie within Eocene sequences mainly 

composed of sandstone. The lone lignites are widely 

known for their unusual wax production. Petrographically, however, the Mount Diablo and lone coals 

are similar. They contain very high amounts of liptinite 

(originating from spores, cuticle, resin, and wax), but few 

layers of clean huminite (wood, bark, root material). In 

both, the total amount of liptinite is difficult to analyze 

because much of it is fine broken detritus. The lone 

lignites contain thin as well as massive cutinite bands, 

blebs of probable cuticular wax, dispersed microspores, 

isolated oval resin bodies, and peculiar "horsehair" layers 

of vesiculated resin rodlets. The dominant identifiable 

liptinites in the Mount Diablo coals are microspores and 

resins, and they show an unusual display of exsudatinite 

(from resinite) that filled fractures in two directions 

normal to bedding. Both coals have distinct microscopic 

structure parallel to the gross bedding but do not contain 

prominent beds of massive "wood" and fine attritus that 

are characteristic of many other United States coals. 

Especially in the lone samples, the structure suggests 

accumulation of a full gamut of plant organs and tissues 

but severe decay of most humic tissues. The Mount 

Diablo coal contains abundant pyrite that occurs as 

dispersed framboids, veins that filled bedding partings 

during early diagenesis, and later cleat fillings. The lone 

lignite has little pyrite. 
Another northern California coal formerly mined 

near Covelo, 140 miles north of San Francisco, is within 

a fault-bounded sliver of probable Eocene and Miocene 

strata within the coastal Franciscan terrain. The coal is 

much less liptinitic than the lone or Mount Diablo coals, 

and it has very abundant fungal sclerotia. It contains an 

unusual petrified log within the coal. Lignites still farther 

north, near Hayfork and Douglas City in Trinity County, 

are entirely woody where sampled; they occur in shallow 

basins and may be Pliocene. 

Hydrogen indexes of 100-200 and oxygen indexes 

of 50-250, from programmed pyrolysis, confirm the 

humic composition of the Hayfork, Douglas City, and 

Covelo coals. In contrast, the Mount Diablo and lone 

coals contain hydrogen indexes of 200-400, and isolated 

"chocolate" layers at lone have unusually high hydrogen 

indexes of 600 like pure resinite. The wax product from 

lone has twice the hydrogen of resin layers. After 

crushing and wax extraction, the lignite residue retains a 

hydrogen index of 200, and many liptinite fragments are 

not visibly altered by extraction; the wax product 

apparently is derived mainly from actual cuticular waxes, 

not from the hydrogen-rich resins or microspores. 

These northern California coals display great 

compositional diversity: some have very high content of 

liptinite, including wax; others consist of intact tree 

trunks and roots; some layers are mainly pollen and 

spores or resin. The few analyses reported for other 

California coals indicate that some of them also may have 

a high content of liptinite. Thus the main interest for 

mining is in the hydrogen-rich California coals, which 

yield chemical specialty products. The total coal resource 

in California is small, but the coal-based wax industry at 

lone is important nationally; and it may lead the way to 

uses more valuable than combustion for other special 

coals in the United States. A second interest is that these 

coals would have served as petroleum source rocks 

where they were deeply buried. The source-rock 

potential of a given volume of these coals may be as high 

This Eocene coal from Mount Diablo, California, has a relatively high content of primary plant resins like many 

Tertiary coals. This resinite fluoresces bright orange-yellow (white in these photos) when illuminated under the 

microscope by ultraviolet or blue light. Compaction during peat-lignite-coal diagenesis causes injection of the 

resinite into tension fractures adjacent to resin bodies, as in left photo, as well as movement of resin or resin 

products into "tectonic" fracture systems such as the in-echelon fractures on the right. The bulk of this coal is 

fiine layers of highly biodegraded plant debris; the layering shows well in these photos because of the fine 

white flecks, mostly plant microspores, that fluoresce almost as brightly as the resin it e. Polished section, water 

immersion optics, mercury vapor illuminator; left photo 0.12X0.18 mm, right 1.4X2.1 mm. [Diagonal gray 

band is plastic used to mount the coal for examination.] By Neely H. Bostick. 

5 
as 15 times that of shales with a comparable type of 

organic matter favorable for generating oil. 

Characterization of Coals in the Lower 

Part of the Williams Fork Formation, 

Twentymile Park District, 

Eastern Yampa Coal Field, 

Routt County, Colorado 

Michael E. Brownfield and Ronald H. Affolter 

Fifty-five bench channel and core samples were 

collected and analyzed from three mine localities in the 

Twentymile Park district, eastern Yampa coal field, 

northwest Colorado. These alluvial plain coals of the 

Upper Cretaceous Williams Fork Formation consist of 

(from top to bottom) the Lennox, Wadge, and Wolf 

Creek beds. The Wadge and Wolf Creek beds are 

overlain by lagoonal and nonmarine sediments and have 

similar elemental composition. Both are low in sulfur 

(Wadge, 0.46; Wolf Creek, 0.65 percent) and ash 

(Wadge, 8.5; Wolf Creek, 10 percent) content. The upper 

portion of the Lennox coal is burrowed and is directly 

overlain and influenced by a bioturbated marine 

transgressive sandstone. The Lennox bed has a higher 

mean sulfur content (2.67 percent) and lower mean ash 

content (6.4 percent), and higher contents of Fe, Hg, As, 

and Br (9, 3.5, 3.8, and 2 times higher respectively) when 

compared to the Wadge bed and higher contents of Fe, 

Hg, and As (5.5, 3.5, and 2.3 times higher respectively) 

when compared to the Wolf Creek bed. 

X-ray diffraction analysis of low-temperature ash 

(LT A) and parting material reveals a predominance of 

well-crystallized kaolinite and quartz, and minor 

amounts of highly expandable clay minerals for all three 

beds. Sanidine, plagioclase (andesine?), barite, gypsum, 

pyrite, and apatite were found in the coal L TA and 

parting material. The Lennox bed LTA contained pyrite 

and ankerite/dolomite when compared to the LT A from 

the Wadge and Wolf Creek beds. 

Several altered volcanic-ash partings-tonsteinswere found in both the Wadge and Wolf Creek coals. 

Coal from the Wadge bed near the volcanic-ash partings 

shows barium and strontium contents 6 times higher and 

phosphorus contents 12 times higher than the average 

values for these elements from other Yampa field coals. 

X-ray diffraction, chemistry, and scanning electron 

microscope with energy-dispersive X-ray capability 

indicate the presence of hydrated aluminum-phosphate 

minerals of the crandallite group. The crandallite 

minerals occur as 1- to 3-micrometer anhedral to subhedral grains. Energy-dispersive X-ray data indicate that 

the crandallite group minerals present in the Wadge bed 

6 

are mainly crandallite with minor amounts of gorceixite. 

That all samples displayed variable Ba, Ca, and Sr 

contents supports a solid solution mode of occurrence. 

The enrichment of Ba, Sr, and Pis, in part, the result of 

the alteration of apatite-bearing air-fall tuffs that were 

deposited into the reducing environment of the coal 

swamp. The close association of the crandallite minerals 

with the clay fraction and the lack of evidence of these 

minerals replacing kaolinite suggest an authigenic origin. 

The crandallite minerals probably formed during early 

diagenesis of the peat swamps and were localized in and 

near kaolinitic altered volcanic-ash partings. 

The Use of Basin Classification and 

Analog Basins in 

Petroleum Resource Assessment 

Mark W. Bultman 

Two things are important for assessing the amount 

of ultimately producible petroleum from an unexplored 

basin. First, the size distribution of oil fields in the basin 

will indicate the nature of hydrocarbon occurrence in the 

basin. Second, the richness factor for the basin 

(ultimately producible oil per unit volume of sediments) 

controls the amount of oil in the basin and is directly 

related to the oil field size distribution and the total 

number of oil fields in the basin. 

In general, the oil field size distribution and 

richness factor of an unexplored basin can only be 

estimated by analogy, through the use of an analog basin. 

Considering the tectonic and geologic histories of the 

unexplored basin and possible analogs leads to a choice 

of a working analog. 

In the analysis described here, the sample 

distribution of oil field sizes from basins in the 

contiguous United States was used to test the hypothesis 

that basins with similar tectonic settings have similar oil 

field size distributions and similar richness factors. The 

primary source of data used in the analysis was a 1981 

excerpt from the TOTL file of the Petroleum Data 

System of North America. 

A flexible three-parameter function, the first 

derivative of the Richards growth function, was used to 

model the distribution of oil field sizes within the 

sedimentary basins of the contiguous United States. The 

Richards function allows oil field size distributions which 

are right or left skewed as well as symmetric to be 

represented quite accurately. The Richards function was 

reparameterized in order to obtain parameters directly 

related to the geometric properties of the curve. 

The most recent version of the Klemme basin 

classification system (published in 1983 by H.D. 
Klemme) was used to place petroleum-producing basins 

of the United States into their appropriate tectonic 

settings. The parameters of the Richards function were 

used to compare basins both within and across these 

tectonic settings. These parameters were found to be 

related to the tectonic setting of the basin to some extent. 

Classical multidimensional scaling was applied to 

the parameterizations of the oil field size distributions in 

the basins. This technique allowed distance between 

distributions to be represented in two dimensions and 

suggested a basin classification system based on the oil 

field size distributions of the basins. This classification 

system consists of the following five categories: (1) craton 

interior shallow and craton margin shallow (foreland) 

basins; (2) craton interior deep basins; (3) craton margin 

deep basins; (4) craton margin-Rocky Mountain basins; 

(5) convergent margin rifted basins. This is similar to 

Klemme's 1980-version classification system, except that 

Klemme's Gulf Coast "downwarp" basins could not be 

differentiated from craton margin deep basins. 

The ultimately producible oil from each basin was 

estimated using production data from the Petroleum 

Data System, and this estimate, in turn, was used to 

create a richness factor for each basin. In general, 

richness was found to be extremely variable, both within 

and across tectonic basin types. Rifted convergent margin 

basins displayed a much higher richness factor than other 

basins, but still displayed a large amount of intra-group 

variance in the richness factor. 

It is possible in some cases to use geologic analogy 

to transfer the sampled oil field size distribution from a 

mature analog basin to an unexplored, frontier basin. 

That the richness factor of a basin is not strongly 

N 

1600 

correlated to the basin's tectonic setting, however, 

indicates that a basin may need to be at least partially 

explored before techniques using geologic analogy can be 

of any use in petroleum resource assessment. An a priori 

choice of richness factors based on tectonic setting alone 

may result in very misleading resource estimates. 

The Midcontinent Rift in the 

Lake Superior RegionStructural Interpretation from 

Deep Seismic Reflection Profiling 

W.F. Cannon, John Behrendt, and A.G. Green1 

Deep seismic reflection profiling in Lake Superior 

and Lake Michigan was conducted in August and 

September 1986 as part of the Great Lakes International 

Multidisciplinary Program on Crustal Evolution 

(GLIMPCE). The surveys were funded by the U.S. 

Geological Survey and the Geological Survey of Canada. 

Data were recorded for 20 seconds so that 

structures as deep as about 60 km could be detected. The 

profiles reveal clear images of the 1.1-b.y.-old Keweenawan rocks within the rift, and of fault and fold structures 

that produced rift basins that are locally as much as 30 

km deep (fig. 1). 

Sections of basalt, as thick as 20 km, produce very 

strong packages of layered reflectors that can be traced to 

or correlated with basalt sequences on land. Sedimentary 

1

Geological Sutvey of Canada, Ottawa, Ontario. 

1900 2200 2500 2800 

s 

3100 

Figure 1. A portion of a reflection profile in eastern Lake Superior. Very strong reflectors are from a thick section of 

Keweenawan basalt and extend as deep as about 30 km beneath CRP 1600. Less reflective sedimentary rocks overlie the basalts 

and are as much as 8 km thick. 

7 
sequences as much as 10 km thick overlie the basalt and 

also occur in flanking basins. The profiles clearly show 

major graben-boundary growth faults which were active 

throughout most of the volcanic activity, so that the 

greatest thicknesses of basalt are within the central 

grabens of the rift and much thinner basalt sections occur 

flanking the grabens. 

Subsidence of central rift grabens was highly 

variable along the rift. In western Lake Superior 

subsidence was highly asymmetrical: the north side of the 

graben subsided much more than the south side. The 

sense of asymmetry changes abruptly along strike from 

the western to the central part of the lake; there, 

subsidence was greatest on the south. Beneath eastern 

Lake Superior the structure is symmetrical, indicating 

uniform subsidence. 

These relationships, along with the gravity 

expression of the rift, indicate that subsidence occurred 

as separate, independent blocks, each with its own 

subsidence history. The volcanic and sedimentary fill of 

the rift can be expected to change substantially along the 

rift trend in response to these varying subsidence 

histories and varying graben geometries. 

Allogenic Processes in the 

Central Sumatra Basin-A Modern 

Analog for the Origin of 

Lower Pennsylvanian Coal-Bearing 

Strata in the Eastern United States 

C. Blaine Cecil, Frank T. Dulong, James C. 

Cobb, 1 Supardi/ and Peter Turnbull3 

The first phase of a study of modern analogs of coal 

formation was conducted in coastal Sumatra and the 

Straits of Malacca during the summer of 1987. This 

region was selected for study because the geologic setting 

appears to be analogous to that of a variety of coalbearing sequences. The study area covers approximately 

30,000 km2 within the central Sumatra basin. The study 

area is bounded on the southwest by upland soils that are 

at the inland margin of coastal peat deposits, on the 

northwest by the Siak River, on the southeast by the 

Kampar River, and on the northeast by the Straits of 

Malacca. The bounding rivers are estuaries that are 

strongly influenced by tides ( > 2 m, 80 km inland from 

the coast). 

Allogenic processes of subsidence, climate, and 

eustacy control both physical and chemical 

1

Kentucky Geological Sutvey, Lexington, KY. 2

Directorate of Mineral Resources, Bandung, Indonesia. 3

P.T. Utah Indonesia, Jakarta, Indonesia. 

8 

sedimentation in the region. Subsidence of the central 

Sumatra basin is associated with wrench faulting and 

oblique subduction along the Sunda Trench. The tropical 

everwet climate of the region is the result of the 

permanent equatorial low-pressure zone (tropical 

convergence). Eustatic changes in sea level appear to 

have occurred during the last 5,000 years. 

On the basis of data from 36 marine and estuarine 

bottom cores, sediments deposited by physical processes 

have a texture range of clay to coarse sand and a 

mineralogy comprising clay minerals and quartz. Of the 

36 cores, shell fragments were found in only the top of 

two cores from the Straits of Malacca. Chemical 

sediments consist of domed-peat on the coastal plain and 

on offshore islands (Neuzil and others, this volume). 

Physical sedimentation is controlled by tidal 

currents in the rivers and by tidal and geostrophic 

currents in the Straits of Malacca. Eroding coastlines in 

the area are indicative of marine transgression. The 

bottoms of the Siak River, the Straits of Malacca, and the 

associated inter-island straits are also erosional, due to 

strong tidal currents. Sediment reworking and deposition 

are limited to the estuarine portion of the Kampar River, 

the estuary-mouth bar of the Siak River, and the confluence of the inter-island straits associated with the Straits 

of Malacca. All our observations indicate that the 

modern sedimentary system is sediment starved. The 

available sediment appears to be transported by tidal and 

geostrophic currents northwestward through the Straits 

of Malacca toward the Andaman Sea. 

Many of the conditions in the study area appear to 

be analogous to those that controlled sedimentation for 

the Lower and lower Middle Pennsylvanian strata of the 

Eastern United States. These conditions include a tectonically active basin, a tropical everwet climate, and eustatic changes in sea level. The interaction of these allocyclic 

processes in Sumatra have resulted in a sedimentstarved, tidally dominated sedimentary system in which 

thick, laterally continuous peat deposits form 

contemporaneously with extensive marine erosion. Such 

conditions may have been responsible for the formation 

of most of the Lower Pennsylvanian coal beds and for 

erosion that led to the Mississippian-Pennsylvanian 

unconformity in the east-central and southern 

Appalachian basin. Our data are also consistent with a 

tidal-origin interpretation for most of the quartzose 

sandstones of the Upper Mississippian and Lower 

Pennsylvanian of the central and southern Appalachian 

basin. 
Paleoenvironmental and Source Rock 

Assessment of Black Shales of 

Pennsylvanian Age, Powder River and 

Northern Denver Basins 

J.L. Clayton, J.D. King, C.M. Lubeck, J.S. 

Leventhal, and T.A. Daws 

Thin Middle Pennsylvanian (Desmoinesian) 

organic-rich black shales (cumulative thickness <50ft) 

underlie much of the northern Denver basin and 

southeastern Powder River Basin. In the Powder River 

Basin, these shales are part of the middle member of the 

Minnelusa Formation. During Desmoinesian time, the 

present -day area of the southeastern Powder River Basin 

and Nebraska was a shallow, at times highly saline, 

restricted sea. In contrast, in the present -day area of 

northeastern Colorado, black shales were deposited in a 

marine environment with normal salinity which was 

probably continuous with the midcontinent Pennsylvanian sea. 

Assessment of paleoenvironment has been carried 

out using organic geochemical parameters. Shales 

deposited in the restricted basin setting contain abundant 

porphyrins (25,000-30,000 ppm relative to total 

extractable organic matter) and significant quantities of 

aryl isoprenoids. The aryl isoprenoid compounds (1) are 

evidence for the presence of the sulfur bacteria families 

Chlorobiaceae and possibly Chromatiaceae and (2) 

indicate that euxinic conditions existed in the water 

column. High ratios of sulfur to carbon in the shales 

support this interpretation. In contrast, extracts from 

black shale in the normal sea to the south contain lower 

porphyrin concentrations (generally less than 1,000 

ppm), and aryl isoprenoids are minor constituents or are 

absent. Sulfur/carbon ratios in these latter shales are 

similar to those observed for normal marine shales (that 

is, not euxinic conditions). Other paleoenvironmental 

indicators (sterane composition, alkane distribution) are 

consistent with these observations. 

Bulk organic matter in the black shales from both 

environments is type II and has good source potential for 

generation of liquid hydrocarbons during catagenesis. 

Pyrolysis yields of 50 kg/ton ( 50,000 ppm) are common, 

and in some shales, yields reach 100 kg/ton (100,000 

ppm). 

Hydrocarbon Distribution in the 

Cretaceous-Tertiary Sagavanirktok 

Formation, North Slope, Alaska 

T.S. Collett and K.J. Bird 

New insights on the Sagavanirktok Formation as an 

important North Slope hydrocarbon reservoir rock unit 

9 

are provided by C.M. Molenaar and others' 1986 

subsurface correlation sections and ongoing USGS 

studies of gas hydrates and basin evolution. Detailed 

correlation sections in the Prudhoe-Kuparuk region and 

analyses of gas samples show that more heavy oil resides 

in Sagavanirktok sandstone reservoirs than previously 

reported, that several areally extensive gas hydrate 

deposits are present, and that the gas in the hydrate 

deposits likely originated through a combination of biogenic and thermogenic processes. 

Throughout Cretaceous and Tertiary time on the 

North Slope, clastic debris shed northward from the 

rising ancestral Brooks Range filled the adjacent foredeep and prograded northeasterly across the subsiding 

Barrow arch to form a passive margin sequence, 

collectively known as the Brookian sequence. The nonmarine to shallow-marine Sagavanirktok Formation and 

its finer grained marine partial equivalent, the Canning 

Formation, form one of the thickest (0-2,700 m) clastic 

wedges in this sequence. The Sagavanirktok Formation 

consists of Late Cretaceous through Tertiary shallowmarine shelf and delta plain deposits composed of 

sandstone, shale, conglomerate, and coal. The areal 

distribution of the Sagavanirktok is limited to the coastal 

plain of the eastern half of the North Slope and the 

adjacent continental shelf. 

Hydrocarbon occurrences within the Sagavanirktok Formation have been known since early exploratory 

drilling in the Prudhoe Bay area, and from earlier studies 

of outcrops to the south. Two oil-bearing sandstone 

intetVals in wells from the Kuparuk area, informally 

named the West Sak and U gnu sands, are estimated by 

ARCO Alaska to contain an in-place oil volume of 21 to 

36 billion barrels. The oil in the West Sak sands ranges 

from 16 to 22 degrees API gravity and contains methane 

through pentane gases in solution. Oil in the lower Ugnu 

sands ranges from 8 to 12 degrees API gravity, and 

methane is the only gas in solution. Our analysis of well 

logs shows that the West Sak and U gnu sands are not the 

only oil-bearing horizons within the Sagavanirktok of the 

Kuparuk River area: in some wells, rock units stratigraphically above the Ugnu sands contain oil columns more 

than 20 m thick. Outside the Kuparuk River area, the 

Sagavanirktok Formation is also oil bearing at Milne 

Point, Point Thomson, and east of the Kuparuk River oil 

field in the Prudhoe Bay oil field area. 

Gas hydrates, crystalline compounds of water and 

gas, occur within the Sagavanirktok Formation. Direct 

evidence comes from a core recovered by Exxon 

Corporation in the Northwest Eileen-2 well, located 25 

km west of Prudhoe Bay, and indirect evidence has been 

obtained from our analysis of open-hole geophysical 

logs-the most useful of these being the resistivity, 

acoustic transit-time, and the gas chromatograph on the 

mud log. We have mapped six laterally extensive gas 
hydrate accumulations in the Prudhoe-Kuparuk area. 

One rock unit in the southern part of the Kuparuk area 

contains gas hydrate, coal, and oil. 

Previous investigators have suggested that the oil, 

and presumably the associated gas, within the Cretaceous 

and Tertiary sandstones of the Prudhoe-Kuparuk area 

were "spilled" from the underlying Prudhoe Bay Sadlerochit structure as a consequence of regional tilting 

during mid to late Tertiary time. Our analyses of canned 

drill-cutting samples provided by ARCO Alaska from 

several development wells in the Kuparuk River oil field 

suggest that the gas hydrates contain a mixture of biogenic and thermogenic gases. The gas in the Sadlerochit 

is thermogenic; therefore, not all of the gas in the 

Sagavanirktok Formation is from the underlying Prudhoe Bay Sadlerochit structure. 

Correlation of Facies Using Chemical and 

Maceral Data in the C Coal Bed, 

Emery Coal Field, Utah 

Sharon S. Crowley and Ronald W. Stanton 

Facies in 11 cores of the C coal bed, Ferron 

Sandstone Member of the Mancos Shale {Cretaceous) 

were correlated using cluster analysis of chemical and 

maceral data. The use of chemical and maceral data 

enabled correlations to be made that were more precise 

than previous correlations based on the physical 

description of the cores. Chemical data for 26 elements1 

were determined in 146 coal and 40 rock samples. The 

data were reported on (or calculated to) a sample ash 

basis from atomic absorption, emission spectrographic, 

X-ray fluorescence, or neutron activation analyses. 

Maceral data included point counts of 23 macerals (using 

reflected white and fluorescent light on polished pellets) 

for 14 pairs of coal samples taken from above and below 

tonsteins. The results indicate that facies within the C 

coal bed can be delimited by their chemical and maceral 

compositions, and that these compositions were 

apparently affected by volcanic ash falls. A cross section 

of 5 of the 11 cores is depicted in figure 1. 

Q-mode cluster analysis of the chemical data 

{grouping of samples into clusters of similar 

composition) produced seven major clusters with 

distinctive chemical characteristics (fig. 1 ). The following 

comparison of clusters is based on the mean values of 

elements in each cluster. Clusters I and II contain a large 

number of samples that have a high ash content; these 

clusters are characterized by relatively low levels of all 26 

1

Sm, Eu, Ce, V, U, Ni, Co, Yb, Lu, Y, Be, Sc, Nb, Zr, Hf, Th, Ta, 

Se, Pb, Zn, Cr, Li, Al, Cu, Ti, Ga. 

10 

elements except for AI {Al2 0 3 =35 percent in cluster II). 

Cluster III consists primarily of coal samples that contain 

intermediate levels of the elements studied, with the 

exception of relatively high Li values of 118 ppm. Cluster 

IV samples generally came from the lower part of the 

coal bed, and they were commonly taken from localities 

adjacent to tonsteins or shales associated with tonsteins. 

These samples are also characterized by intermediate 

levels of all 26 elements. Cluster V, comprising samples 

taken from near the base and top of the C coal bed, 

contains relatively high levels of several elements 

including Ni {105 ppm), Co (78 ppm), Zn {140 ppm), and 

Cr {83 ppm). Cluster VI consists of four samples, taken 

directly below the "upper" tonstein in all but one case. 

This cluster is characterized by high average concentrations of Zr {1,240 ppm), Nb {66 ppm), and Ce (485 

ppm) compared to the other clusters. Cluster VII 

comprises six coal samples taken directly adjacent to 

tonsteins in all cases, primarily between the "doublet" 

tonsteins. This cluster contains relatively high 

concentrations of Zr (765 ppm), Nb (63 ppm), Th {81 

ppm), and Hf {22 ppm). Leaching of volcanic ash or 

incorporation of ash in peat layers is interpreted to have 

contributed to high levels of several elements that 

characterize clusters VI and VII. For example, the tonstein minerals zircon and ilmenite may have provided 

sources for high levels of Zr and Nb, respectively, in 

cluster VI. 

Q-mode cluster analysis of the maceral data 

produced two major clusters (fig. 1). Cluster A samples 

contain abundant inertinites (mean values= 38 percent 

inertinites, 57 percent vitrinites, 5 percent exinites) and 

were taken directly below tonsteins, whereas cluster B 

samples contain abundant vitrinites (mean values= 14 

percent inertinites, 81 percent vitrinites, 5 percent exinites) and generally came from above tonsteins. The 

inertinites are composed primarily of semifusinite, a 

maceral generally accepted as forming under oxidizing 

conditions. Abundant semifusinite below tonsteins may 

reflect better drained swamp conditions than those that 

existed after the volcanic ash falls. 

Inorganic and Organic Geochemical 

Cycles in Petroleum Source Rocks of the 

Cretaceous Western Interior SeawayRecords of Paleoceanographic Change 

Walter E. Dean, Michael A. Arthur, and 

Lisa M. Pratt 

Two major transgressive episodes in the 

Cretaceous western interior seaway resulted in the 

deposition of organic-carbon-rich pelagic carbonate 
as Q6 

Q9 010 

- I·.· 1 ~ + + •111 111 111111111111 11 ~:.~ 111111 f: + lllllllllllllllllll -

'] 1 F~ rl~l·::=l I ------- :;1= n• 

• 

Figure 1. Correlation of samples from five cores of the C coal bed using chemical and maceral clusters. 

111°15'oo 

_L 

•013 

N 

•012 I •011 

0 10 

09 

08 

•07 

•03 

1Mi 

1----i 

1Km 

H 

1-38°52' 30 

Clusters 

Maceral Chemical 

DA + IIIIJ] 

[838 . §11 . 

:::::::::::: Ill 

-IV 

Utah ~v 

stwdy .VI 

Area 

~VII 

• Tonsteins 

D Data not available 

• Shales, siltstones, claystones 
% CaC03 

25 50 75 870~~~~~~~ 

100 

890 

900 

rn 

~ 910 

Q) 

-+-) 

Q) 

s 

~ 920 ...... 

~ Q) 930 ~ 

940 

950 

970~~~~~~~ 

0 

25 50 75 100 0 

% CaC03 

% Al 

4 

4 

% Al 

8 

8 

0 

0 

% Org. C 

2 4 

2 4 

% Org. C 

6 

6 

Pierre 

Shale 

upper 

chalk 

upper 

marl 

middle 

chalk 

middle 

marl 

lower 

chalk 

lower 

marl 

'-

<D 

.c 

E 

<D 

~ 

I 

>-

~ 

0 

E 

(J') 

lower chalk 

and shale 

Fort Hays 

Member 

Figure 1. Geochemical logs of percent CaC03 , aluminum (AI), and organic carbon (Org. C) for the Smoky Hill 

Member of the Niobrara Formation in the Coquina Oil, Berthoud State #4 well, Larimer County, Colorado. Dashed 

line through each log is a smoothed curve of the data computed using a spline smoothing function. 

units, the Niobrara Formation and the Bridge Creek 

Limestone Member of the Greenhorn Formation. 

Although these two units are of minor stratigraphic 

significance compared to the thick siliciclastic sequences 

deposited during periods of lower sea level, they 

represent a major potential as petroleum source rocks. 

12 

Geochemical logs of cores of the Niobrara and 

Greenhorn from eastern Colorado show pronounced 

cycles whose periods range from tens of thousands to 

several million years. The longer-period cycles are 

illustrated for the Niobrara Formation (fig. 1) by logs of 

CaC03 , aluminum (AI), and organic carbon (OC). The 
smoothed logs of CaC03 and AI (dashed lines in fig. 1) 

show distinct cycles on a scale of 30 m that correspond to 

the chalk and marl units of the Niobrara described in a 

1964 study by G .R. Scott and W .A. Cobban. Within the 

30-m cycles are sub-cycles that average about 5 m thick 

and show up in figure 1 as minima on the CaC03 log and 

maxima on the Allog within the marly units. The 5-m 

cycles also appear on down-hole sonic logs of the Niobrara Formation reflecting a greater degree of lithification of the limestone beds relative to the marls tone beds. 

The 30- and 5-m cycles can be seen in outcrop but are 

best observed in geochemical and geophysical logs. 

The most visible cycles in cores and outcrops of 

both the Niobrara and Greenhorn are bedding cycles of 

limestone and madstone that are several decimeters 

thick. The darker colored, marlstone beds contain more 

organic matter, higher concentrations of many trace 

elements, higher Sr:Ca ratios, and lower values of o

18 0 

than the limestone beds. The geochemical evidence 

confirms the importance of fluctuating freshwater runoff 

to the basin in producing changes in sediment supply and 

water column stratification, with consequent oxygen 

depletion and enhanced preservation of marine organic 

matter in the basin. 

Although considerable uncertainty exists in the 

Cretaceous time scale, the periodicities of the bedding 

(decimeter) cycles in the Niobrara and Greenhorn and 

the 5-m and 30-m cycles in the Niobrara are estimated to 

be several tens of thousands of years, several hundreds of 

thousands of years, and several million years, 

respectively. G.K. Gilbert in 1895 was the first to suggest 

that the bedding cycles of the Niobrara and Greenhorn 

were related to global climate change driven by variations 

in the Earth's orbital characteristics, and that these cycles 

might be used to calibrate geologic time. Subsequently, 

the striking similarity of bedding cycles in many different 

marine carbonate sequences separated in space (global) 

and time (at least Mesozoic and Cenozoic), and the close 

correspondence of the estimated periodicities of some of 

these cycles to the Earth's orbital cycles (Milankovitch 

cycles) have been pointed out by numerous investigators. 

These cycles, therefore, may provide a stratigraphy of 

global and regional paleoceanographic events. 

The pronounced rhythmic bedding of the 

carbonate units in the southern part of the western 

interior seaway resulted from climatic sensitivity of 

pelagic and hemipelagic depositional processes in that 

part of the basin, which was an arm of the northwestern 

margin of the Tethys ocean during maximum 

transgressions. It is the unique setting and climate 

sensitivity that has contributed to the periodic 

preservation of primarily marine organic matter, an 

unusual feature of pelagic carbonate facies. The 

enhanced preservation of organic matter occurred during 

periods of time when bottom-water masses were anoxic 

13 

to slightly oxic as a result of increased water-column 

stabilization created by increased freshwater runoff into 

the basin. Organic carbon concentrations as high as 7 

percent and pyrolysis hydrogen indices as high as 650 

characterize some of the marly to shaly beds in each of 

the carbonate units indicating that both units have 

significant hydrocarbon generating potential. The 

northern and western parts of the seaway were shallower, 

more restricted, and less sensitive to climatic 

perturbations and, therefore, filled with more 

homogeneous clastic units. 

Active Folding in the Hispaniola-Caicos 

Basin and Tectonic Control of 

Sediment Distribution Pathways from the 

Hispaniola Insular Margin 

W.P. Dillon, K.M. Scanlon, N.T. Edgar, 

and L.M. Parson1 

Ridges that trend at a shallow angle to the northern 

insular margin of the island of Hispaniola are disclosed 

by seismic-reflection profiles and GLORIA long-range 

sidescan-sonar imagery collected in the HispaniolaCaicos Basin north of Haiti. Seismic profiles show that 

the ridges are anticlinal structures, having fold 

amplitudes that increase both downward and toward the 

insular margin. The lack of magnetic anomalies 

associated with the folds suggests that the structures, 

both in the deep basin and on the steep insular margin, 

do not involve basement. We conclude that here, at the 

boundary of the North American and Caribbean plates, 

the basin deposits are being progressively crumpled 

against the island block in the form of growth anticlines 

as a result of basin-floor movement west-southwest 

relative to the island of Hispaniola. Tightly folded and 

upraised basin deposits form the steep northern insular 

slope. 

The sidescan imagery shows that the tectonic 

ridges extend diagonally away from the Haitian margin in 

a west-northwest direction. This ridge pattern creates 

parallel channelways that extend into the HispaniolaCaicos Basin, and these channelways and interruptions 

present in the ridges seem to control the transport of 

sediment from the island of Hispaniola to the abyssal 

plain of the basin. One large fan debouches onto the floor 

of the basin from the end of a fold -controlled channelway 

off the central part of the northern Haiti insular margin. 

1

Institute of Oceanographic Science, United Kingdom. 
A Rationale for the Method of 

Estimating the Number of 

Small Undiscovered Oil and Gas Fields 

L.J. Drew, J.H. Schuenemeyer, and E.D. Attanasi 

Our study provides a rationale for the method of 

estimating the number of small oil and gas fields 

remaining to be discovered in partially explored regions. 

In these regions, small fields contain most of the 

undiscovered conventional oil and gas resources. Our 

rationale is that (1) the underlying field size distribution 

is log-geometric in form, and (2) the apparent declining 

frequency in the smaller size classes is a consequence of 

an economic filtering or truncation process. 

This rationale has been developed and tested using 

data from the Minnelusa and Frio plays, the Texas State 

and Federal waters, the western Gulf of Mexico offshore, 

the Denver and Permian basins, the North Sea, and world 

offshore. From analyses performed in these nine 

exploration plays, basins, and larger areas, we have 

demonstrated that the observed relative frequency of 

fields in the smaller size classes is directly related to the 

cost of discovery and of developing oil and gas fields. 

Moreover, further study of several of these basins 

showed that the mode of the observed field size 

distribution shifted to smaller size classes when oil and 

gas prices increased. 

A discovery process model was used in conjunction 

with the log-geometric assumption to estimate a factor, r. 

This factor represents a multiplier such that the ultimate 

number of fields in each size class has r times the number 

of fields in the next size class larger. This factor was 

computed using the estimated ultimate number of fields 

from those field size classes thought to be unaffected by 

economic truncation. In size classes unaffected by 

economic truncation, the discovery process model was 

used to predict the ultimate number of fields which 

occur. The resulting r-factor was then applied to the field 

size classes affected by economic truncation to estimate 

the number of fields occurring in these size classes. 

GLORIA Sonographic Mosaics of the 

Bering Sea and the Western 

Aleutian Arc and 

Adjacent North Pacific 

EEZ-Scan Bering Sea1 and Aleutian Arc2 Groups 

1

P.R. Carlson, A.K Cooper, J.V. Gardner, R.E. Hunter, H.A. 

Karl, M.S. Marlow, A.J. Stevenson (U.S. Geological SuiVey); Q. 

Huggett, N.H. Kenyon, and L.M. Parson (I.O.S., Wormley, U.K). 

14 

Since 1984 the U.S. Geological Survey has 

cooperated with the Institute of Oceanographic Sciences 

(U.K.) to survey the Exclusive Economic Zone (EEZ) of 

the United States. The principal mapping tool is the 

GLORIA system, a long-range sonar. Bathymetry, highresolution seismic-reflection, dual-channel air-gun, 

gravitational and magnetic field data are collected i.n 

addition to the wide-swath sonar. Among the geologic 

settings investigated during the 4 years of the project is 

the Bering Sea-Aleutian arc region, a sedimentologically 

and tectonically complex area of plate convergence. 

Three cruises in 1986 and one cruise in 1987 surveyed 

about 850,000 km2 of the EEZ in the Bering Sea from 

Unimak Pass northwest to the U.S.-U.S.S.R. Convention 

Line of 1867. Two cruises in 1987 surveyed about 

400 000 km2 of the western Aleutian arc and trench and ' adjacent North Pacific seafloor from Adak Island 

westward to the 1867 Convention Line and from the 

200-m isobath seaward 375 km (200 n.m.) to the 

boundary of the U.S. EEZ. 

Some of the largest submarine canyons in the world 

incise the Beringian margin. These canyons, particular Iy 

Navarinsky, Pervenents, and Zhemchug, have been 

excavated principally by mass wasting. The products of 

mass transport range from small slides and slumps less 

than 1 km2 in area to slides of several hundred square 

kilometers. No large channels extend onto the basin floor 

from the mouths of the canyons along the Beringian 

margin northwest of Bering Canyon, which suggests that 

those canyons contribute only small amounts of modern 

sediment to the Aleutian Basin. Three channels that 

issue from Bering, Umnak, and Pochnoi canyons are the 

primary conduits through which sediment is dispersed to 

the abyssal floor of the Aleutian Basin. The extent of 

these channels, which cross the abyssal seafloor for 

several hundred kilometers, was unknown prior to the 

GLORIA survey. Bering channel, the most prominent, 

feeds sediment to the Bering fan, which is characterized 

by a complex acoustic backscatter pattern. The other 

channels also transport sediment to this area, which 

appears to be the primary locus of modern deposition in 

the southeastern part of the Aleutian Basin. 

Large amounts of sediment are shed to the basin 

floor from the Aleutian and Bowers Ridges. The erosion 

of these ridges is being expedited by tectonic uplift 

leading to unstable, oversteepened slopes. The apparent 

youthfulness of seafloor scarps, submarine volcanoes, 

and basement ridges beneath the crest and flanks of 

Bowers Ridge suggests that Bowers Ridge is presently 

being uplifted as well as eroded. In contrast, the abyssal 

basin areas of the Bowers Basin and southwestern 

2

R.G. Bohannon, B.D. Edwards, H.A. Karl, T.L. Vallier 

(USGS); M.F. Dobson (University of Wales at Abecystwyth); and D. 

Masson (I.O.S., Wormley, U.K.). 
Aleutian Basin appear to be tectonically stable and 

receiving mostly pelagic sediments. 

The seafloor morphology and the geology south of 

the Aleutian arc are dominated by subduction tectonics. 

Structurally controlled submarine canyons head on the 

shelf summit arc platform, but do not debouch onto the 

floor of the Aleutian trench; instead they terminate in 

forearc basins that are filled with thick sediment 

accumulations. Subtle pathways of sediment dispersal 

are seen on the sonographs where sediment has spilled 

over from sediment-filled forearc basins onto the trench 

floor. A small canyon that has developed on the 

accretionary wedge south of Amchitka Island, possibly by 

mass wasting, shows an active channel that appears to be 

feeding a fan on the trench floor. Tectonic elements 

within and near the subduction complex include a flat 

trench floor, landward-verging thrusts in the accretionary 

prism, and faults on the seaward slope of the trench that 

are oriented subparallel to the direction of plate 

convergence. Stalemate ridge, a small piece of Kula 

plate, and the extinct Kula-Pacific ridge are tectonic 

elements of particular interest on the North Pacific 

seafloor. Collision of the Stalemate ridge (extinct KulaPacific transform fault) with the arc margin has caused 

extreme deformation of the forearc that includes, for 

example, uplift of the trench floor of more than 500 m 

relative to other parts of the trench. 

Available Coal Resources-A Pilot Study 

Jane R. Eggleston, M. Devereux Carter, and 

James C. Cobb1 

According to the Energy Information 

Administration of the U.S. Department of Energy, the 

United States currently has more than 400 billion tons of 

coal in the Demonstrated Reserve Base. The reserve 

base includes coal that is available for mining, and its 

estimate is determined by applying designated bed 

thicknesses, mining depths, and reliability factors to a 

geologically derived coal-resource data base. However, 

this methodology for estimating coal available for mining 

ignores many geologic, environmental, engineering, and 

economic factors that further restrict the availability of 

minable coal. When these additional factors are 

considered, the amount of coal actually available for 

mining may be significantly reduced. Although attempts 

have been made to define available coal, none have used 

a comprehensive, point-source, geologic data base and 

1

Kentucky Geological Sutvey, Lexington, KY 40506-0056. 

15 

incorporated all the geologic, land-use, cultural, and 

engineering restrictions currently placed on the mining of 

coal. 

To quantify these restrictions and to determine 

their impact on available coal resources, a pilot study in 

the Appalachian region has been initiated by the U.S. 

Geological Survey in cooperation with the Kentucky 

Geological Survey. The Matewan 7Y2-minute quadrangle, 

Pike County, eastern Kentucky, was selected for the pilot 

study. Factors that limit the availability of coal for surface 

and underground mining, defined as restrictions, were 

compiled at 1:24,000 scale. The U.S. Geological Survey's 

National Coal Resources Data System (NCRDS) was 

used to assemble and manage the data base for all 

geologic and mining data. For surface mining, 

environment-related restrictions are surface features that 

are immovable and that generally must have barriers left 

around them. These restrictions include: (1) major 

powerlines and pipelines, (2) towns and public buildings, 

(3) federal highways, (4) cemeteries, (5) oil and gas wells, 

( 6) railroads, and (7) environmentally sensitive areas, 

such as endangered species habitats, protected rivers, 

game lands, lakes, and parks. In addition, surface mining 

is restricted by the limiting strip ratio that can be 

achieved and still be economic. Restrictions on 

underground mining are primarily economic and 

technologic. A coal bed will not be mined if: (1) it is 

either too shallow or too deep; (2) it is within a certain 

distance above or below an active/abandoned mine or 

coal bed which is more likely to be mined; (3) it is located 

in highly folded or faulted areas; ( 4) roof or floor 

conditions would be too problematical; and (5) the coal 

bed is too thin to be mined by conventional technology. 

Coal quality may be a restricting factor if the coal does 

not meet compliance standards for sulfur or if it does not 

meet user specifications. 

All these factors were entered into NCRDS and 

applied to the remaining coal resource estimate for the 

Matewan quadrangle to derive the available coal 

resource estimate. Initial investigations on the Upper 

Elkhorn No.2 coal indicate that of the 106 million short 

tons of original coal resources, 92 million short tons now 

remain after mining, and only 28 million short tons, or 30 

percent of the remaining coal, is actually available for 

mining. If other factors such as percent recovery and 

mining economics are considered, available coal is 

further reduced. 

The data for the Matewan quadrangle may be 

extrapolated some distance, but only as far as the 

geologic, environmental, engineering, and economic 

conditions remain relatively uniform. Additional studies 

are required to determine if the results for this 

quadrangle are representative of other areas of the 

Appalachian basin. 
Basin Evolution and Upper Paleozoic 

Coal Deposits in the 

Central Appalachian Basin 

Kenneth J. Englund and Roger E. Thomas 

The distribution and character of upper Paleozoic 

coal beds in the central Appalachian basin were 

influenced by a series of terrestrial depositional events 

associated with basin evolution. Most sediment 

originated as siliciclastic detritus eroded from tectonic 

highlands that were elevated by plate collision along the 

southeastern margin of the basin. Deposition occurred in 

a slowly subsiding foreland basin occupied mostly by 

northwestward-prograding delta lobes and, to the 

northwest, on an unstable cratonic shelf covered by a 

shallow epicontinental sea. A transition from terrestrial 

to marine deposition is recorded by time-equivalent 

sequences of coal and related swamp accumulations, 

fluvial and deltaic sandstone, lagoonal and bay-fill shale, 

barrier- and offshore-bar sandstone, and marine shale 

and limestone. Terrestrial progradation was dominant 

during periods of high rainfall and sufficient subsidence 

to accommodate the influx of sediments. Conversely, 

marine incursions extended farthest southeastward 

during periods of diminishing rainfall and minimal 

sediment influx. When the shift from regression to 

transgression was gradual and near equilibrium existed 

between marine and terrestrial influences, stillstands of 

sea level coincided with widespread peat accumulations 

and barrier- and offshore bar development. As the 

Appalachian basin evolved, the shoreline or wedge-out of 

terrestrial deposition shifted gradually northwestward 

and rotated from N. 30° E. in Early Mississippian time to 

N. 65° E. in Early Pennsylvanian time (fig. 1). This 

change in the sedimentary trend coincided with a similar 

rotation in the deformational strike of the faulted and 

folded Appalachians which may have resulted from plate 

rotation during collision. Coal bed characteristics 

including rank, ash and sulfur contents, and selected 

trace elements in coal ash also exhibit trends that can be 

related to basin evolution. 

Analcime in Coal Beds of the 

Wasatch Plateau, Utah-Geological and 

Technological Significance 

Robert B. Finkelman 

Sodium is generally believed to be a major 

contributor to fouling and corrosion of coal-fired boilers 

and to agglomeraton in fluidized-bed combustors. Most 

16 

sodium in coal beds is also generally believed to be in 

either (1) ion-exchange sites in organic matter or in clay 

minerals, or (2) solution. 

A recent study of 27 samples from Upper 

Cretaceous coal beds of the Wasatch Plateau, Utah, 

reveals that much of the sodium in these beds occurs in 

an unusual mode-as analcime, a hydrous sodium 

aluminum silicate. Analcime was detected in 23 of the 27 

samples. In the high-sodium coal beds in the central and 

southern parts of the plateau, as much as 90 percent of 

the sodium is present as analcime. The analcime occurs 

primarily as fracture fillings in the coal beds and, to a 

lesser extent, as cell fillings in coal macerals of the 

inertinite group. 

The unusual mode of occurrence of sodium in the 

Wasatch Plateau coal beds has potentially important 

consequences. 

• Awareness of the structural, hydrologic, 

geologic, and geochemical controls on analcime 

distribution should help in developing an exploration 

strategy for low-sodium coal. The textural evidence 

indicates that analcime in the coal is clearly of secondary 

origin. Analytical data from local water samples were 

tested using a chemical equilibrium modeling program to 

determine the source of the analcime. The results 

indicate that the analcime and the associated epigenetic 

minerals (calcite and pyrite) could have precipitated 

from water from the underlying aquifer, the Ferron 

Sandstone Member of the Mancos Shale. The higher 

sodium concentrations in the plateau coal beds occur 

along the trace of the synclinal axes in the Ferron 

between the Pleasant Valley and Joes Valley fault 

systems. It is likely that the distribution of analcime (and 

therefore of sodium) was controlled by the fault pattern 

and the potentiometric surface of the Ferron aquifer. 

• Sodium occurring in a mineralogical form such as 

analcime is not as likely to contribute to boiler fouling as 

much as organically associated sodium. This may explain 

why the Wasatch Plateau coals, even with relatively high 

sodium content, are not known to cause boiler fouling. 

• Because of the unusual mode of occurrence of 

sodium in coal beds of the Wasatch Plateau, the various 

empirical fouling indices are not applicable. These 

indices assume that sodium in coal is in a volatile form. 

• It will be possible to use weathered samples of 

coal for evaluation of the sodium distribution in areas of 

the plateau where fresh samples are unavailable. 

Examination of samples from deeply weathered outcrops 

of coal revealed the presence of relict analcime as well as 

the residual and weathering products (quartz and kaolinite). 

• It appears that conventional coal-cleaning 

procedures could effectively remove sodium (as well as 

much of the ash) from this coal. A laboratory density 

separation removed approximately one-half of the anal-
~ TERRESTRIAL 

COAL-BEARING 

ROCKS 

0 150 KM 

0 90 Ml 

GEORGIA 

N 30° E 

INDEX MAP 

Figure 1. Map of the Appalachian basin showing the northwestward wedge-out of terrestrial coal-bearing 

rocks in the Price {1), Bluestone (2), Pocahontas (3), and New River (4) Formations or correlatives and the 

relation of sedimentation trends to the strike of major structural trends of the faulted and folded Appalachians 

(heavy lines). Dashed formation line, extension beyond control. 

cime with a concomitant loss of less than 10 percent of 

the coal. Perhaps the resultant analcime-rich concentrate 

could itself be marketed for one of the many purposes for 

which zeolite minerals are commercially used. 

• Because analcime is not preferentially 

concentrated within a particular coal bed, selective 

mining techniques to reduce sodium content will not be 

effective. 

• Mining of coal and leaching of coal in stockpiles 

should not significantly contribute to the deterioration of 

surface-water or ground-water quality through the 

release of sodium, because sodium in these coals occurs 

largely in a non-water-soluble mineral form. 

17 

Offshore Resource Geology of 

Selected South Pacific Island NationsThe USGS SOPAC Program 

H. Gary Greene, Michael S. Marlow, David W. 

Scholl, and John G. Vedder 

The USGS's geoscientific program in the 

Southwest Pacific (SOPAC) is coming to an end in 1988 

after 5 years of intensive marine geophysical 

investigations in the waters of Papua New Guinea 

(PNG), Solomon Islands, Vanuatu, and Tonga. The data 

collected in these regions during the 7 months of 

surveying by the S.P. Lee consist of 24-channel CDP, 

single-channel airgun, Uniboom, and 3.5-kHz seismic-
reflection profiles; sonobuoy wide-angle seismic reflection/refraction; and gravity and magnetic profiles. These 

data, as well as seafloor photographs, sediment samples, 

and rock samples, were used to assess the hydrocarbon 

potential of this region. 

Thick sequences of sediment mapped throughout 

the'region range from approximately 3 km thick on the 

southern Tonga platform to as much as 8 km thick in the 

Queen Emma Basin of eastern PNG. Sediment thickness 

increases from south to north along the active island arcs 

of Tonga, New Hebrides, and Solomon Islands. The 

thickest and most extensive sedimentary units underlie 

the intra-arc basins of Vanuatu, Solomon Islands, and 

eastern PNG. These basins resulted from complex Neogene tectonic events that include subduction, subduction 

polarity reversal, and oblique ridge-arc collisional events. 

These tectonic processes induced wrench-faulting, with 

associated horsts and basin-forming grabens. Thick 

deposits of eroded carbonate and volcaniclastic sediment 

from adjoining islands, as well as pelagic material, 

accumulated in the grabens. 

Oil seeps reported in Tonga, Fiji, and Vanuatu 

indicate that hydrocarbons have been generated in these 

regions. Onshore source-rock analyses suggest only a 

remote potential for the generation of gas, and none for 

oil. Drilling both onshore and offshore in Tonga and Fiji 

has not recovered hydrocarbons. However, reevaluation 

of old geophysical data along with the interpretation of 

the new USGS data has shown new targets. For example, 

buried reefs have been located in offshore Tonga, and 

structural traps occur along the basin flanks in Vanuatu, 

Solomon Islands, and PNG. A "bright spot" or acoustical 

geophysical anomaly was discovered in New Ireland 

Basin, PNG, suggesting hydrocarbons trapped within the 

basin. Much more work needs to be done in these regions 

to fully understand the energy and mineral resources. 

Laramide Thrusting of the 

Bighorn Mountains onto the 

Powder River Basin near 

Buffalo, Wyoming 

J.A. Grow, E.N. Hinrichs, J.J. Miller, 

M.W. Lee, and S.L. Robbins 

Recent seismic surveys and exploratory drilling by 

industry for subthrust oil and gas prospects beneath the 

Bighorn Mountain front along the western edge of the 

Powder River Basin near Buffalo, Wyoming, reveal a 

basement-involved thrust of considerable magnitude. A 

deep test for oil and gas, the Arco 1-4 Kinney Ranch 

borehole, was drilled 13 km (8 mi) west of Buffalo and 

penetrated 750 m (2,460 ft) of Precambrian granite 

18 

gneiss before penetrating the thrust and entering 1,475 m 

(4,838 ft) of the Paleocene Fort Union Formation and 

another 2,199 m (7,212 ft) of Mesozoic and Paleozoic 

sedimentary rocks. The Gulf Granite Ridge 1-9-2D 

borehole, which was drilled 31 km (19 mi) 

north-northwest of the ARCO borehole and 5 km (3 mi) 

northwest of Story, Wyoming, penetrated 1,768 m (5,800 

ft) of granite before entering Upper Cretaceous strata. 

This borehole penetrated a total of 3,021 m (9,910 ft) of 

Mesozoic and Paleozoic sedimentary rocks. 

Chevron U.S.A., Inc. supplied to the USGS two 

very high quality seismic reflection profiles near the 

Kinney Ranch and Granite Ridge boreholes. These 

profiles have been reprocessed by the USGS and 

integrated with surface geologic mapping, gravity 

surveys, and other geologic studies by the USGS in 

progress in the Powder River Basin. The seismic profiles 

near the Kinney Ranch and Granite Ridge boreholes 

clearly show that sedimentary rocks of Paleozoic through 

Paleocene age, which occur beneath the thrust fault, 

extend more than 11 km (7 mi) westward from the 

eastern edge of the basement thrust. The fault plane at 

the base of the Precambrian granites and gneisses dips 

30° to the west. Although exploration for oil and gas plays 

beneath basement overthrusts along the Bighorn 

Mountain front has not been successful to date (fall 

1987), information derived from this effort provides 

valuable insight into the tectonic processes along Laramide overthrust zones and the techniques required for 

future exploration. 

Organic Geochemical Studies of the 

Early Coalification of Peat and 

Associated Xylem Tissue 

Patrick G. Hatcher, Harry ·e. Lerch Ill, T.V. 

Verheyen1 , and M.A. Wilson2 

Organic geochemical investigations of peat, coal, 

and associated xylem tissue from both gymnosperms and 

angiosperms have provided useful information on the 

organic transformation processes collectively known as 

coalification. The combined use of solid-state 13C 

nuclear magnetic resonance (NMR) and pyrolysis/gas 

chromatography/mass spectrometry (py/gc/ms) allowed 

us to examine the organic composition of these materials, 

on both a bulk (average) compositional and a detailed 

molecular basis. From the study of angiosperm and 

gymnosperm xylem we conclude that coalification 

1

Coal Corporation of Victoria, Churchill, Victoria, Australia. 2Commonwealth Scientific and Industrial Research 

Organization, North Ryde, NSW, Australia. 
C-C-C C-C-C C-C-C 

OCHa OH 

0-

guaiacyl-based lignin 

acatechol-like 

structures 

aphenols and 

alkyl phenols 

C-C-C C-C-C C-C-C 

CH 3 0 OCH 3 

0-

OH 

0- 0-

syringyl-based lignin catechol-like 

structures 

guaiacyl-based 

structures 

Figure 1. Proposed coalification pathways for lignin. 

involves the following processes: 

1. Early selective removal of cellulose so that lignin, the 

primary constituent of xylem, in turn becomes the 

macromolecular aromatic components in coal. 

2. Modification of both angiosperm and gymnosperm 

lignin by demethylation reactions to form catechollike structures (fig. 1). In angiosperms, the syringylbased lignin is more rapidly transformed than the 

guaiacyl-based lignin. Eventually, the aromatic 

angiosperm residues begin to resemble those of 

coalified gymnosperm wood, which is primarily 

derived from guaiacyl-based lignin. 

3. With increasing coalification to subbituminous coal, 

the resultant xylem becomes selectively enriched in 

specific phenols and alkylphenols as the catechol-like 

structures decrease, indicating a dehydroxylation 

process. 

In our studies of coal and its precursor, peat, the 

coalification of xylem tissue only partly explains the 

19 

overall transformation. Other substances such as 

degraded algae, bark, leaf material, oxidized wood, and 

other plant remains can be recognized as chemically 

contributing to the organic composition of our peat and 

coal samples. The chemistry of such contributors and the 

processes by which these components become coalified 

are complex and not -well known. However, one process 

that appears universal to nearly all chemically altered 

plant remains is the degradation and loss of 

carbohydrates. Another process that can be discerned is 

the selective degradation of aromatic components 

relative to aliphatic components (such as resins, waxes, 

and cuticles). The extent of degradation is partially 

dependent on the degree of oxidation of the peat. Thus, 

changes in aromaticity within a coal bed may reflect 

differences in source contributions and (or) differences 

in degree of oxidative degradation. The latter process, if 

quantifiable, may aid in identifying facies variations 

within coal beds. 
Phosphorus Burial in the 

Deep Sea During the 

Past 125 Million Years 

James R. Herring, Walter E. Dean, and 

Michael A. Arthur1 

Much of the effort applied to the study of 

commercial-grade sedimentary phosphate deposits has 

been with the hope that the temporal and spatial record 

of these deposits would provide clues assisting the search 

for new deposits. Inventories have been made of 

phosphatic deposits through time searching for periodicities, common environments, or depositional 

mechanisms. These inventories focus only on the 

enriched phosphatic deposits and ignore the lesser 

concentrations of organic phosphorus (Porg) in deep-sea 

sediments, although the enormous volume of deep-sea 

sediments suggests that this reservoir of P org might be 

important to the overall global phosphate cycle and, 

hence, to the occurrence of enriched deposits. Estimates 

of phosphate burial in the deep sea have been difficult to 

obtain because the ubiquitous and often dominant 

inorganic phosphorus component in crustal rocks cannot 

be differentiated from the P org content. However, we 

have devised a method to determine the inorganic 

phosphorus content of these pelagic sediments; thus we 

are able to calculate p org contents. 

In order to differentiate the rate of burial of P org 

from that of total phosphorus (Ptot) we have used the 

aluminum-Ptot ratios for several localities throughout the 

Atlantic and Pacific Oceans, each chosen to represent 

one of three types of depositional environments for the 

inorganic contribution to marine sediments: terrigenous, 

hemipelagic, and eolian. A plot of the Al:Ptot ratio allows 

us to estimate the contribution of inorganic phosphorus, 

which then is subtracted from the Ptot concentration and 

leaves the fraction of the phosphatic material resulting 

from biogenic processes (Porg). Our inventory of 

sedimentary P org for Cenozoic and Upper Cretaceous 

deep-sea sediments is several hundred times larger than 

published inventories of commercial phosphatic deposits 

over this same interval, indicating that the P org content of 

deep-sea sediments indeed is a major part of the global 

sedimentary phosphate cycle. Only subtle changes in the 

Porg content incorporated in deep-sea sediments through 

time would be necessary to produce the amounts of 

phosphate that occur in typical, large commercial 

deposits, for example those of western Africa or the 

southeastern United States. This phosphate then would 

1

Graduate School of Oceanography, University of Rhode Island, 

Naragansett, RI 02882. 

20 

need to accumulate in a local environment favorable for 

phosphatic enrichment, deposition, and preservation. 

We also have examined relationships among AI, 

organic carbon (Corg) and Ptot in Cretaceous and Tertiary 

deep-sea sediments. A ternary diagram of weight percent 

concentrations of Al, Corg and total phosphorus X 100 

(Ptot X 100) provides a convenient way of examining 

relationships among these three variables in corg -rich 

sediments. An Al:Prot X 100 ratio of about 1:1 represents 

the crustal average, and this line on a ternary diagram 

provides a convenient reference for measuring phosphate 

enrichment or depletion relative to the crustal 

concentration. A Corg:Ptot X 100 ratio of about 1:1 

represents the Redfield ratio of these two elements in 

living organic matter. Oxidative decay of organic matter 

usually results in a progressive loss of P org relative to 

Corg' which increases the Corg:P ratio. Most Cretaceous 

Corg -rich strata recovered from Atlantic DSDP sites 

show what is essentially dilution of terrigenous detritus 

with Corg and a slight enrichment in Ptot· Most sample 

sets show considerable variation in the Corg:P ratio with 

both enrichment and depletion in Ptot relative to the 

Redfield ratio. 

Burial History Reconstruction of the 

Lower Cretaceous J Sandstone in the 

Wattenberg Field, Colorado, "Hot Spot" 

O.K. Higley and D.L. Gautier 

A Wattenberg Field thermal anomaly or "hot spot" 

is recognized by analysis of present-day geothermal 

gradient and thermal maturity data from the Denver 

basin. Thermal maturity was determined in the Wattenberg Field and across the basin by sampling and analyzing 

the Lower Cretaceous J sandstone and adjacent 

hydrocarbon source rocks for percent mean random 

vitrinite reflectance (Rm ). The degree of source rock 

thermal maturity is primarily affected by burial depth, 

with resultant thermal and diagenetic effects. The highest 

Rm values occur north of the structurally deepest part of 

the Denver basin, in the Wattenberg Field of 

southwestern Weld County. Comparison of Rm data to 

burial depth throughout the Denver basin indicates that 

the "hot spot" has anomalously high Rm values, ranging 

from 1.05 to 1.51 percent at current depths of 7,000 to 

8,000 ft. 

TTl burial history analysis was used to characterize 

the J sandstone thermal history both within and outside 

the Wattenberg Field. Burial history reconstructions of 

coreholes within the "hot spot" used the present -day 
geothermal gradient range of 2.0-2.9 °F/100 ft, 

considerably higher than the 1.6-2.0 °F/100 ft present in 

most of the Denver basin. 

Outside the "hot spot," calculated TTl's correlate 

to present -day Rm data for the J sandstone, suggesting 

that most of the Denver basin experienced only minor 

heat flow fluctuations from Albian to the present. 

Assuming current geothermal gradients were present 

from the time of J sandstone deposition, the Wattenberg 

Field has anomalously high TTl's compared to Rm 

values. 

The burial history of the #1 G.W. Steiber Unit 

Amoco well, SW SW 24, T. 1 N., R. 67 W., was calculated 

with the present-day geothermal gradient of 2.55 °F/100 

ft and an assumption of 2,550 ft of eroded sediment, most 

of which eroded from Miocene time to the present. The 

calculated 687 TTl is approximately equivalent to an Rm 

of 1.9 percent. The measured Rm is considerably lower at 

1.14 percent, indicating that the J sandstone in this 

corehole was subjected to lower heat flows in the past, 

resulting in a lower thermal maturity level than is 

indicated with the current geothermal gradient. 

The Wattenberg Field lies along a series of 

northeast -trending basement lineaments that define the 

Colorado Mineral Belt. Activation of these basement 

structures, especially during and after the Laramide 

orogeny, may have influenced the heating history of 

overlying sediments by increased heat input and through 

more efficient heat flow along associated faults and 

fractures. Wattenberg Field burial history reconstructions that assume a lower geothermal gradient prior 

to the Laramide orogeny, about 68 million years ago, 

result in a closer correlation of TTl to measured Rm data 

and indicate that the Wattenberg Field area was 

subjected to lower geothermal gradients in the past. 

Faulting and Folding on the 

Eastern Flank of the Bighorn 

Mountains, Sheridan and 

Johnson Counties, Wyoming 

E. Neal Hinrichs 

Recent information from seismic surveys, boreholes, and geologic mapping has clarified the structure of 

the eastern flank of the Bighorn Mountains in Sheridan 

and Johnson Counties, Wyoming, especially the 

subsurface extent of basement-involved thrust faults. 

These mountains in north-central Wyoming trend northnorthwest near the eastern edge of the Rocky Mountain 

foreland and separate the Bighorn and Powder River 

Basins. 

21 

The core of this range consists of Precambrian 

igneous and metamorphic rocks, chiefly granitic rocks of 

Middle and Late Archean age (2,900-3,200 Ma), and 

dikes and plugs of mafic and ultramafic rocks of Late 

Archean age (2,600-2,800 Ma). The structural grain of 

the Precambrian rocks trends generally northeast, 

parallel to the grain at the southern edge of the Powder 

River Basin. Surrounding the core are sedimentary rocks 

of Cambrian to Oligocene age totalling about 5 km thick. 

Those best exposed are the Ordovician Bighorn 

Dolomite, the Mississippian Madison Limestone, and the 

Pennsylvanian Tensleep Sandstone. 

The Bighorn Mountains can be divided into three 

structural blocks, northern, southern, and central, on the 

basis of directions of structural movement. The northern 

and southern blocks were transported southwestward, as 

indicated by pairs of folds overturned to the southwest 

and by eastward-dipping, high-angle reverse faults. The 

central block, however, displays evidence of transport to 

the east-northeast over a thrust fault that dips 30° to the 

west. This central block is approximately 28 miles in the 

north-south dimension and consists of the Piney lobe, 

Mowry Basin, and the Johnson Creek-Crazy Woman 

Creek segment. Primary thrust faults and secondary 

strike-slip faults, many of which involve Precambrian 

rocks, cut the central block. A large thrust fault under the 

Piney lobe shows clearly on a seismic profile (courtesy of 

Chevron U.S.A., Inc.) that extends southwest from the 

town of Big Horn past a borehole at Granite Ridge to 

Penrose Park. A thrust fault in the Johnson Creek-Crazy 

Woman Creek segment is represented on a second 

seismic profile that extends east along French Creek 

about a mile north of the borehole at Kinney Ranch. The 

thrust faults in the central block are offset by strike-slip 

and normal faults, some of which are extensions of 

reactivated Precambrian faults. One of these extensions 

has right lateral displacement and extends southwestward into a dike of diabase and diorite. 

In comparison to the Piney lobe and the Johnson 

Creek-Crazy Woman Creek segment, the Mowry Basin 

is a topographic low over a structural high. The top of the 

Tensleep Sandstone in the Reasor 1 Tarbet borehole, in 

the southern part of Mowry Basin, is about 2,500 ft 

higher than in the borehole at Granite Ridge and about 

1,500 ft higher than in the borehole on Kinney Ranch. 

Uplift along east-west faults is probably the main cause 

of the structural high. Several visible faults separate 

Mowry Basin from the rest of the central block. Some of 

the uplift probably was caused by concealed faults, 

including the Buffalo Deep fault, a major reverse fault 

that trends northwest between the Tarbet and Granite 

Ridge boreholes. The petroleum potential of Mowry 

Basin is a function not only of structurally high reservoir 

rocks, but also of hydraulic connection to source beds, 

mainly Cretaceous marine shales beneath the thrust 
fault. This connection may have been severed by 

numerous faults which may also have contributed to 

reduction in porosity. Knowledge of the tectonic history 

gained through geologic mapping, subsurface drilling, 

and geophysical data is essential in the assessment of 

exploration targets along complex compressional 

mountain fronts such as the Bighorns. 

The tectonic history of the area during the Laramide orogeny began with uplift of the Bighorn 

Mountains and (or) subsidence of the Powder River 

Basin, late in the Paleocene Epoch. The resultant syntectonic conglomerates in the upper part of the Fort Union 

Formation and the lower part of the Wasatch Formation 

were deposited along the eastern front of the mountains. 

Near the end of the Eocene Epoch, regional east-west 

compression caused thrust and strike-slip faulting that 

delineated the three structural blocks in the Bighorn 

Mountains. 

Supergene Enrichment of Sulfur in 

Coal Deposits of the Powder River Basin 

Charles W. Holmes and Anthony B. Gibbons 

The lower Tertiary of the Powder River Basin, 

northeastern Wyoming, consists of terrestrial siltstones, 

sandstones, and coals of the Paleocene Fort Union and 

the Paleocene and Eocene Wasatch Formations. The 

thick coals are considered to be of high quality as they are 

generally low in sulfur; however, some zones of high 

sulfur ( > 4.0 percent) are present in the basin. The sulfur 

content of coals from the Wasatch Formation ranges 

from 0.3 to 6.4 percent; the sulfur content of coals from 

the Fort Union Formation ranges from 0.1 to 5.2 percent. 

Samples of coal and associated strata collected 

from drill holes in the Powder River Basin show that the 

total sulfur distribution in the subsurface defines three 

distinct zones. In rocks within approximately 15 m of the 

surface, sulfur content ranges from 0.1 to 0.25 percent. 

At depths between 15m and 45 m, the sulfur content of 

the rocks increases to levels between 1.0 and 5.5 percent. 

Below 45 m sulfur contents decrease slightly to range 

between 0.75 and 1.25 percent. The boundaries of these 

zones follow the local topography, and cut across the 

westward-dipping strata. Coal beds intersecting the 

enriched zone show a definite localized increase in sulfur 

content within the zone. 

Most of the sulfur in the surface zone occurs as 

sulfate in the mineral gypsum. In the intermediate 

enriched zone and in the lower reduced zone, sulfur 

occurs as a sulfide primarily as pyrite. The distribution of 

sulfur isotopes ranges from -7.5 a34S (CDT) in the 

surface zone to + 2.1 o

34S (CDT) in the enriched zone. 

22 

This evidence indicates that much of the sulfur in the 

enriched zone was derived from the overlying oxidized 

zone. The sulfur enrichment thus appears to result from 

geochemical processes similar to those that form rollfront uranium or supergene metal deposits. Oxidizing 

meteoric waters migrating downward through the 

sediments carry dissolved sulfur species to lower depths 

where reduction reactions predominate. Here the sulfur 

forms sulfides and over time accumulates to form a 

sulfur-enriched zone. If this zone intersects coal, the 

elevated chemical potential present in the organic 

material of the bed would tend to enhance the sulfur 

concentration over that of the adjacent non-organic 

rocks. 

Santa Maria Project, 

Central California Coast 

C.M. Isaacs and R.G. Stanley 

The Santa Maria Project, jointly undertaken under 

the U.S. Geological Survey's Evolution of Sedimentary 

Basins Program and the Onshore Oil and Gas 

Investigations Program, focuses on the tectonically active 

south-central California continental margin. The study 

covers the onshore region west of the Sur-Nacimiento 

fault and north of the Santa Barbara Channel together 

with adjacent offshore areas, a region embracing the 

onshore Santa Maria basin proper, offshore Santa Maria 

basin, Pismo basin, Huasna basin, and several other 

small basins and basin fragments. The Santa Maria 

province contains the world's largest diatomite deposit as 

well as major deposits of petroleum ( > 1 billion bbl), tar 

sand, heavy oil, and oil shale. The province also includes 

the most extensive fractured petroleum reservoirs in 

California and, in the offshore, the largest United States 

petroleum discoveries since Prudhoe Bay. 

The Santa Maria province has had a complex 

tectonic history. Mesozoic and lower Paleogene rocks 

form a collage of tectonostratigraphic terranes that 

apparently accreted to the North American continent by 

late Eocene time. Many questions remain about the sites 

of origin of the terranes, their travel paths, and the 

processes and timing of terrane suturing and continental 

"docking." Overlying pre-Eocene strata and fragments of 

Eocene marine and Oligocene-Miocene nonmarine clastic strata are deposits in numerous economically 

important basins, which began to form along the 

continental margin at about the Oligocene-Miocene 

boundary. Miocene to Pleistocene strata deposited in 

these basins include clastic marine and nonmarine strata, 

minor volcanics, and the organic-rich biogenous strata of 

the Miocene Monterey Formation, the source of 
diatomite and petroleum deposits. The origin of the 

Neogene basins is controversial; wrench tectonism, 

regional extension, and large-scale block rotation are 

among proposed mechanisms. Differences among 

models are so great that Miocene paleolocations, 

onshore-offshore orientations, and basin geographies are 

completely uncertain. However, Miocene facies and their 

subsequent structural, thermal, and compaction history 

critically controlled petroleum generation and reservoir 

formation. 

Major geologic problems addressed by the project 

are thus: (1) the origin and timing of terrane accretion; 

(2) the origin and history of the Neogene sedimentary 

basins; (3) Miocene paleogeography and lateral facies 

variations; and ( 4) the thermal and structural history of 

the province. Excellent surface exposures occur on the 

province peripheries and extensive subsurface data are 

available from both onshore and offshore. Thus the Santa 

Maria province offers an uncommon opportunity to 

resolve major tectonic and paleogeographic problems of 

wide interest and broad application. 

Initial studies in the Santa Maria Project will focus 

on the stratigraphic and structural framework, with 

particular emphasis on detailed mapping in key areas and 

intensive study of important stratigraphic sections in 

outcrops and wells. Specific projects underway or 

planned include: (1) mapping in the Lopez Mountain and 

Point Arguello areas; (2) detailed sedimentologic and 

biostratigraphic study of Oligocene-Miocene nonmarine 

and marine strata; (3) comprehensive dating of Miocene 

volcanic units; and (4) thermal history studies of lower 

Neogene sandstones. In addition, the following regional 

summaries are underway: (1) major cross sections based 

on outcrop, subsurface, and geophysical data; (2) 

compilations of the geology, gravity, and magnetics; (3) a 

series of paleogeographic compilations illustrating the 

geologic evolution of the province from Jurassic to 

Holocene; and ( 4) a synthesis of the basin's geologic 

evolution from Jurassic to Holocene. 

An Assessment of Gas Resources in 

Low-Permeability Sandstones of the 

Upper Cretaceous Mesaverde Group, 

Piceance Basin, Colorado 

Ronald C. Johnson, Robert A. Crovelli, Charles 

W. Spencer, and Richard F. Mast 

Prepared in cooperation with the U.S. Department of Energy, 

Morgantown, W.Va. 

A modified volumetric approach was used to 

estimate in-place and recoverable gas resources in the 

low-permeability sandstones of the Upper Cretaceous 

23 

Mesaverde Group in the Piceance basin of western 

Colorado. For the analysis the Mesaverde Group was 

subdivided into three stratigraphic intervals, the Williams 

Fork Formation, the lies Formation, and the Rollins 

Sandstone Member (of the Mount Garfield Formation) 

or Trout Creek Sandstone Member (of the Iles). Each of 

these three stratigraphic intervals was then subdivided 

into two plays-a deeper gas play, which contains mainly 

sandstones that are gas bearing, and a shallower 

transition play that contains both gas-bearing and waterbearing sandstones. Variations in levels of thermal 

maturity were used to define the boundaries of the three 

deep gas plays and the three transition gas plays. 

Two different methods were used to calculate 

resources. In the first method, the volume of sandstone in 

each of the six plays was calculated directly from 

sandstone isopach maps. Average depth of the play was 

estimated from overburden maps, and these depths were 

used to calculate the average pressure and average 

temperature for each play. An estimate of areal extent, 

average porosity, average gas saturation, and percent 

gas-saturated sandstone was then made for ~ach play. 

This method produced a mean resource estimate for 

each of the six plays. 

In the second method, values assuming different 

levels of probability were assigned to the geologic 

parameters such as play area and sandstone thickness. 

These probability ranges were then run through two 

complex probability programs. The first probability 

program assigns estimates to the gas potential of an 

individual play at the 95, 75, 50, 25, and 5 percent 

probability levels. The second program computes the 

same five probability levels to the aggregated sum of gas 

in all six plays using varying degrees of dependency 

between the plays. Using the aggregation program and 

the most likely degree of dependency of 75 percent 

between the plays, the mean in-place resource for the 

aggregated six plays is 419.55 tcf. There is a 95 percent 

chance of at least 274.45 tcf of in-place gas and a 5 

percent chance of at least 605.33 tcf of in-place gas in the 

Mesaverde. 

Six different recovery factors were estimated for 

each play: a low, most likely, and high recovery factor 

assuming current technology with a gas price of five 

dollars per thousand cubic feet (mcf); and a low, most 

likely, and high recovery factor assuming future advanced 

technology without a gas price specified. The recovery 

factors were applied to the probability ranges calculated 

using the two probability programs. Using the currenttechnology and five-dollar-gas assumptions, the range of 

estimates of recoverable gas for the aggregated six plays 

at the 95 percent, mean, and 5 percent probability levels 

are 2.92, 4.48, and 6.48 tcf for the low estimate; 8.75, 

13.42, and 19.41 tcf for the most likely estimate; and 

29.04, 44.45, and 64.20 for the high estimate. Using 
future advanced technology without a gas price specified, 

the range of estimates is 11.65, 17.85, and 25.80 tcf for 

the low estimate; 44.23, 67.95, and 98.39 tcf for the most 

likely estimate; and 128.04, 196.22, and 283.65 tcf for the 

high estimate. 

Sedimentology of and 

Petroleum Occurrence in the 

Lower Permian Schoolhouse 

Tongue of the Weber Sandstone, 

Northwest Colorado 

Samuel Y. Johnson, Christopher J. Schenk, 

Donald E. Anders, and Michele L. Tuttle 

The Lower Permian Schoolhouse Tongue of the 

Weber Sandstone forms an extensive paleo-petroleum 

reservoir in northwest Colorado. The Schoolhouse 

Tongue is mainly bleached or oil-stained, gray to 

yellowish-gray sandstone of inferred eolian-sand-sheet 

origin. Low-angle (0°-15°) bedded very fine to finegrained sandstone is the dominant facies. Beds are 

typically parallel or are truncated by low-angle 

deflationary surfaces, and deflation lags of coarse sand 

grains and granules are common. Crossbedded dune 

deposits (set thickness generally less than 50 em) are a 

less common sand-sheet facies. Interbedded fluvial 

deposits are present in most sections. The sand-sheet 

deposits of the Schoolhouse Tongue are sedimentologically similar to those in the underlying red beds of the 

Middle Pennsylvanian to Lower Permian Maroon 

Formation, and the Schoolhouse Tongue is best 

construed as the uppermost sand sheet in the Maroon 

depositional sequence. The distinction between the 

Schoolhouse Tongue and the Maroon Formation is 

based on their different diagenetic histories. 

The Schoolhouse Tongue has a maximum 

thickness of 66 m along Rifle Creek, the site of a late 

Paleozoic structural high. Oil staining in this area extends 

several hundred meters downward into the Maroon 

Formation and tens of meters upward into the unconformably overlying Permian and Triassic State Bridge 

Formation and the Triassic Chinle Formation. Away 

from Rifle Creek, the Schoolhouse Tongue thins to the 

north and pinches out (in 40 to 65 km) to the southeast 

and east into the Maroon Formation; and oil staining in 

strata bounding the Schoolhouse Tongue is negligible. 

The distribution of oil-stained rock suggests that 

Oil-stained (gray) and bleached (white) sandstone of the Lower Permian Schoolhouse Tongue of the Weber Sandstone. 

Oil mainly occurs in secondary porosity resulting from migration of precursor organic acids and dissolution of carbonate 

cement. Photograph by S. Y. Johnson, from outcrops on east side of Rifle Creek, Garfield County, Colorado. 

24 
hydrocarbons were introduced at a point source, possibly 

related to faults on the margins of the paleo-high. 

Oil in the Schoolhouse Tongue mainly occurs in 

secondary porosity resulting from migration of precursor 

organic acids and dissolution of carbonate cement. Sulfur 

isotopic data from the oil and from iron sulfides in 

ferruginous concretions are similar, suggesting that iron 

(present originally as grain coatings?) may have also been 

mobilized during this migration. Petroleum was trapped 

below overlying red siltstones of the State Bridge and 

Chinle Formations. Geochemical typing of the 

hydrocarbons in the Schoolhouse Tongue is consistent 

with a late Paleozoic source rock, perhaps the Lower to 

Middle Pennsylvanian Belden Formation. 

Kinetic Models of Organic Reactions 

Applied to Burial History of 

Sedimentary Basins 

J. David King 

The purpose of this study is to apply principles of 

chemical reaction kinetics to the interpretation and 

reconstruction of burial-temperature histories within 

sedimentary basins. The technique produces finely tuned 

time and temperature syntheses that can be used as input 

to other models of oil and gas generation within the 

context of an overall basin analysis. 

An excellent way to illustrate the thermal history of 

rocks penetrated by drilling is to construct a burial 

history with isotherms. These diagrams, which are graphs 

of depth versus geologic age, are constructed by plotting 

different strata at their present -day depth of burial, then 

projecting depth lines back to the time of deposition. The 

major unknown is paleotemperature. As a first 

approximation, the present-day heat flow (or geothermal 

gradient) can be extrapolated into the past. Burial history 

diagrams are frequently used to calculate TTl at 

different depths to determine the thermal maturity of 

possible petroleum source rocks. 

Because the burial history effectively defines the 

time-temperature history of a rock at any depth, it is 

possible to directly calculate expected thermal maturity 

parameters versus depth based on kinetic modeling 

without correlating TTl values to the parameter of 

interest. Comparison of predicted and observed maturity 

values permits refinement of the postulated burial history 

to produce the best scenario. This comparison 

significantly constrains paleotemperature, rock ages, and 

unconformities. 

The basic idea behind kinetic modeling is that 

chemical reactions proceed to equilibrium or completion 

predictably with respect to time and temperature. The 

25 

relationship between time, temperature, and degree of 

reaction is defined by the rate equation for the reaction. 

For any two chemical compounds R and P where it 

is known that R yields P with time and temperature, the 

rate equation for the reaction R-+P can be used to 

calculate present -day amounts of R and P produced by a 

postulated burial-temperature history. Chemical analysis 

of down-hole rock samples for relative amounts of R and 

P provides observed data. If a systematic difference 

appears between calculated and observed quantities of R 

and P, the burial-temperature history can then be refined 

to produce the best match. 

Distribution and Structure of 

Early Mesozoic Rift Basins on the 

Continental Margin of the 

Eastern United States 

K.D. Klitgord and D.R. Hutchinson 

Early Mesozoic rift basins are distributed across a 

300-km-wide zone along the eastern seaboard of the 

United States. In addition to the exposed rift basins such 

as the Newark-Gettysburg basin, numerous rift basins 

have been mapped beneath the coastal plain and on the 

continental margin using seismic-reflection, magnetic, 

and drill-hole data. These rift basins are located within 

the shallow platforms and embayments (less than 5 km of 

postrift sedimentary cover) and along the hinge zone that 

separates these platforms and embayments from the 

marginal basins (such as Georges Bank basin), which 

contain 8-13 km of postrift sedimentary fill. The buried 

rift basins have been traced from the Bay of Fundy 

(Fundy rift basin) southward around the east side of the 

Gulf of Maine embayment, along the western edge of 

Georges Bank basin (Franklin rift basin), and then 

westward across the Long Island Platform (Atlantis, 

Nantucket, Long Island, and New York Bight rift basins). 

Rift basins rim the Salisbury Embayment and include a 

set of small basins on the west side (for example, the 

exposed Richmond Basin) and a set along the hinge zone 

(Delaware Bay and Norfolk rift basins). A rift basin 

(Brunswick rift) lies at the hinge zone between the 

Carolina platform and trough and is marked by the 

magnetic low of the Brunswick Magnetic Anomaly. This 

magnetic low swings westward and crosses onshore near 

Brunswick, Georgia; a rift basin has been imaged on 

seismic data by COCORP beneath this magnetic low. 

Three types of structures appear to have controlled 

formation of rift basins buried on the United States 

continental margin. These structures are: (1) paired 

(antithetic) border faults that extend deep into the crust 

(such as the Long Island rift basin-Block Island fault 
pair), (2) discontinuity or ramp in a buried detachment 

surface near the position of the Appalachian gravity 

gradient (the Newark-New York Bight rift basin pair), 

and (3) low-angle detachment surface beneath the 

continental margin (Norfolk and Franklin rift basins). 

Many of these faults may represent reactivated Paleozoic 

structures. 

Structural character of the rift basins is variable 

along and across the margin. Simple half-graben 

structures are located along the northeastern Georges 

Bank basin, southern Baltimore Canyon trough, and 

Carolina trough hinge zones. Crustal failure near the 

hinge zone in the northern Baltimore Canyon trough and 

southwestern Georges Bank basin created a more 

complex pattern of faulted blocks than the structures 

observed on the rest of the margin. Synrift deposits 

blanket a chaotic set of small prerift(?) crustal fragments. 

We interpret these fragments as debris left on a lowangle (east-dipping) detachment surface that separated 

the North American and African plates during the rifting 

phase. 

Synrift sediment fill for many of the rift basins is 

characterized by tilted, subparallel reflectors landward of 

the basement hinge zone and a wedge-shaped reflector 

geometry seaward of the hinge zone. The change in 

reflector geometry across the hinge zone is a function of 

differential erosion in response to uplift landward and 

greater subsidence seaward of the hinge. A qualitative 

two-stage model of rift evolution explains these changes: 

an early stage is characterized by widespread half-graben 

formation along listric or planar normal faults, and a late 

stage is characterized by uplift and erosion at and 

landward of the hinge. Age control in the offshore region 

is poor, but biostratigraphic age data for synrift and early 

postrift sedimentary deposits and regional tectonic 

evolution models incorporating the European rift 

constraints indicate a Late Triassic age for early rift 

phase, Early Jurassic for the late rift phase, and late Early 

Jurassic for the end of rifting. 

Organic Geochemical Studies of the 

Eastern U.S. Early Mesozoic 

Newark Basin-Phase Two 

R.K. Kotra 

Until recently, organic geochemical investigations 

of lacustrine sedimentary rocks from the Eastern U.S. 

early Mesozoic basins by the U.S. Geological Survey have 

26 

been mostly restricted to outcrop material. During the 

first phase of our investigations, surface samples from the 

Hartford and Newark basins were shown to contain 

sufficient amounts of organic matter of appropriate type 

and maturity to produce fluid hydrocarbons. Pyrolysis, 

chromatography, mass spectrometry, nuclear magnetic 

resonance spectroscopy, elemental ratios, and stable 

isotope ratios were used to determine the amounts, 

types, and maturities of soluble organic matter (bitumen) 

and insoluble organic matter (kerogen). Estimates of the 

nature and amount of the more labile organic 

constituents from outcrop material are probably 

minimum values due to the effects of evaporation, 

oxidation, and weathering. Regional patterns of thermal 

maturation in these basins are currently being evaluated 

using the organic geochemical data from the surface 

samples. 

The second phase of our investigations consists of 

examining continuous rock cores in the Passaic River 

basin in northern New Jersey. In this area exposure of 

sedimentary strata is poor; thus, the core sample set is 

the most complete stratigraphic section across the 

northern portion of the Newark basin. Well-preserved 

material to a depth of about 425 feet has been obtained. 

About 250 samples of red, gray, brown, and black 

mudstone and siltstone were used for organic geochemical studies. Other samples studied included a small 

number of sandstones of varying grain size, some with 

bitumen staining. The intervals represented are the 

Lower Jurassic Boonton, Towaco, and Feltville 

Formations and the Upper Triassic Passaic Formation. 

The results of our first organic analyses of the core 

samples show that the total organic carbon content 

ranges from 0.05 percent to 4.1 percent; and many 

samples contain > 2 percent. Hydrogen index (HI) 

values range from about 20 mglg to more than 500 mglg. 

Many of the gray-black and black mudstones have HI 

values of > 300 mglg. T max values range from about 

425 oc to > 470 °C. Production index values are in the 

range from 0.1 to 0.4 for samples that did not appear to 

be obviously stained with bitumen. These initial results 

indicate that the organic matter spans the marginally 

mature to overmature stage. The HI and T max values of 

individual samples indicate good oil and gas potential. 

Detailed characterization of kerogen and extracted 

hydrocarbons currently underway is designed to derive 

maturation parameters that are less dependent on the 

type of sedimentary organic matter present in these 

samples. This information will facilitate more accurate 

assessment of the abundance and thermal history of 

organic matter in the Newark basin. 
The Role of Thermal History in the 

Preservation of Oil at the South 

End of the Moxa Arch, Utah and 

Wyoming-Implications for the Oil 

Potential in the Southern 

Green River Basin 

B.E. Law and J.L. Clayton 

The production of oil from the Lower Cretaceous 

Dakota Sandstone at the south end of the Moxa arch, 

immediately north of the Uinta Mountains in Utah and 

Wyoming, is unusual because the depth of occurrence is 

greater than 15,000 ft. At comparable depths elsewhere 

in the region, oil would be thermally destroyed. The 

preservation of oil in this area is largely due to an unusual 

thermal history. 

The south end of the Moxa arch has a low thermal 

gradient (approximately 1.0 °F/100 ft) and unusually low 

levels of thermal maturity at depth (less than 0.6 percent 

vitrinite reflectance at 15,000 ft). A vitrinite reflectance 

(Rm) profile from this area shows that the thermal 

maturity gradient from 8,000 to 15,500 ft is very low 

(about 0.05 percent Rm/1,000 ft), indicating a nearly 

uniform distribution of heat. Lopatin-type thermal 

history reconstructions are not compatible with 

measured Rm data. The area is also characterized by the 

occurrence of relatively fresh water in the Dakota 

Sandstone, wherein total dissolved solids (TDS) range 

from 6,000 to 9,000 parts per million (ppm). North of this 

area, the TDS content of water in the Dakota exceeds 

9,000 ppm. Some evidence suggests that these conditions 

also occur in the footwall of the Uinta thrust fault and in 

a narrow, 10- to 20-mile-wide area paralleling the Uinta 

thrust fault in the south end of the Green River basin. 

On the basis of these observations and in the 

context of the geologic history, we suggest that convective 

and (or) advective heat transfer processes have played a 

prominent role in the thermal history of the south end of 

the Green River basin. The observed low level of thermal 

maturity in the Dakota requires a prolonged period of 

low temperature, comparable to the present thermal 

gradient. We conclude that the present thermal gradient 

came into existence in latest Cretaceous or Paleocene 

time, during or shortly after the faulting that occurred 

along the north flank of the Uinta Mountains. The faults 

and fractures, thus formed, provided pathways into the 

deep basin for the circulation of meteoric water. Under 

these conditions, convective and advective heat transfer 

processes effectively reduced the thermal gradient in the 

near vicinity of the Uinta Mountains thrust fault, 

precluding the development of high levels of thermal 

maturity. Thus, preservation of oil in the Dakota 

Sandstone at the south end of the Moxa arch has been 

27 

facilitated by the occurrence of low temperatures that 

have been maintained through a geologically long time by 

convective and (or) advective heat transfer. By analogy, 

the potential for the occurrence of oil in the south end of 

the Green River basin is greatly increased because of the 

effective deepening of the "oil window." 

Assessment of Gas Contained in 

Overpressured Low-Permeability 

Reservoirs in the Greater Green River 

Basin of Wyoming, Colorado, and Utah 

B.E. Law, C.W. Spencer, R.A. Crovelli, R.F. Mast, 

G.L. Dolton, R.R. Charpentier, and C.J. Wandrey 

Prepared in cooperation with the U.S. Department of Energy, 

Morgantown, W.Va. 

The Greater Green River basin of Wyoming, 

Colorado, and Utah contains large amounts of gas in 

overpressured low-permeability Cretaceous and Tertiary 

reservoirs. The stratigraphic sequence in which these 

reservoirs occur reaches thicknesses of as much as 14,000 

ft ( 4,267 m ); it includes the Lower Cretaceous Dakota 

Sandstone and equivalents to the lower Tertiary Fort 

Union Formation. 

The accumulation of thermogenic gas in these 

low-permeability source and reservoir rock sequences at 

rates greater than it is lost causes fluid (gas) pressure to 

rise above regional hydrostatic pressure. Thus, overpressuring is coincident with the occurrence of gas-bearing 

reservoirs. The gas-bearing overpressured sandstone 

reservoirs occupy the deeper parts of the basin, downdip 

from water-bearing normal-pressured reservoirs. 

Structural and stratigraphic trapping aspects in these 

unconventional reservoirs are not as important as in 

conventional reservoirs; the top of overpressuring cuts 

across structural and stratigraphic boundaries. The 

source of the gas is type III organic matter in the 

interbedded coal and carbonaceous lithologies, and type 

II and III organic matter in the interbedded marine 

shales. 

The assessment of gas contained in these overpressured low-permeability reservoirs utilizes a reservoir 

equation in which the gas volumes are expressed as 

functions of the geologic and engineering variables. The 

variables include the areal extent of overpressured gas 

reservoirs, reservoir thickness, porosity, gas saturation, 

reservoir depth (temperature), geothermal gradient, 

pressure gradient, and gas compressibility. 

The gas resource assessment approach is a 

probabilistic play analysis. The quantitative geologic 

model for a play consists of the reservoir equation with 

the geologic and engineering variables treated as random 
variables having probability distributions in the form of 

seven fractiles. The probabilistic methodology used to 

process the geologic data is an analytic method derived 

from probability theory as opposed to Monte Carlo 

simulation. On the basis of this methodology, two 

separate computer programs were designed-one for 

play analysis and another for play aggregation. 

The Greater Green River basin gas-bearing 

interval was subdivided into five stratigraphic plays and 

the gas in-place resource for each play was estimated. 

The aggregate gas in-place resource of these plays ranges 

from 3,631 to 7,128 tcf, with 5,196 tcf as the mean 

estimate. Recoverable gas was estimated for each play 

under the following scenarios: (1) current technology, 

with a gas price of five dollars per thousand cubic feet 

and (2) advanced technology, with no dollar limit. For the 

cu"ent technology scenario, the aggregated recoverable 

gas ranges from 72 to 268 tcf, with 151 tcf as the mean 

estimate. For the advanced technology scenario, the 

aggregated recoverable gas ranges from 222 to 909 tcf, 

with 492 tcf as the mean estimate. For comparison, the 

National Petroleum Council in 1980 estimated the total 

in-place tight gas resource in the Greater Green River 

basin at 136 tcf and the maximum recoverable gas at 86.5 

tcf. These estimates did not, however, include gas deeper 

than 15,000 ft (4,572 m). 

Petroleum Geology of the 

People's Republic of China 

K.Y. Lee and C.D. Masters 

On the basis of geotectonics and geothermal 

gradients, petroleum-producing sedimentary basins in 

the People's Republic of China are grouped into eastern 

and western basins. The eastern basins reached full 

development in the late Mesozoic and Cenozoic as a 

result of extensional tectonics; they are the Songliao, 

North China, Ordos, Sichuan, Jianghan, Nanxiang, Subei, 

Eren, Sanshui, and Bose basins. The western group of 

basins, the Tarim, Junggar, Qaidam, Jiuquan, and Turpan basins, acquired their present configuration as a 

result of compressional tectonics during the early Cenozoic collision of the Indian subcontinent with the 

Eurasian plate. 

Source rocks in both groups of basins consist of 

Mesozoic and Cenozoic, grayish-green and dark-gray to 

black, lacustrine mudstone and shale, except in the 

Junggar and Tarim basins, where Carboniferous and 

Permian marine black shale generated most of the crude 

oil. Higher than average geothermal gradients, which 

range from 30 oc to 70 oc per kilometer, are 

characteristic of the eastern basins. Reservoirs of the 

28 

eastern basins are fluviodeltaic sandstone and Late Proterozoic and Paleozoic carbonate rocks containing 

solution-enhanced fractures and buried-hill traps. 

Reservoirs of the western basins comprise strata of all 

ages; however, fluvio-fan and delta deposits of Mesozoic 

age dominate. Multiple reservoir zones characterize oil 

fields in both groups of basins. 

In 1986, the combined Songliao and North China 

basins produced about 70 percent of the 2.6 million 

barrels of crude oil per day produced in China. The 

remaining 30 percent was produced from the Junggar, 

Tarim, Qaidam, Jiuquan, Sichuan, Ordos, Nanxiang, 

Jianghan, and Bose basins. As of 1985, and cited from a 

1987 study of Masters and others, Chinese crude oil 

identified reserves, both onshore and offshore, were 

assessed at 23.6 billion barrels, with there being a 90 

percent probability that undiscovered recoverable 

resources lie within a range of 20-93 billion barrels of oil; 

natural gas reserves were estimated at 24.8 trillion cubic 

feet, with there being a 90 percent probability of the 

occurrence of undiscovered recoverable resources within 

the range of 122-467 trillion cubic feet of gas. 

Processing Techniques for 

Deep Crustal Marine Multichannel 

Reflection Seismic DataExamples from the Great Lakes 

M.W. Lee, W.F. Agena, and D.R. Hutchinson 

Multichannel seismic reflection data acquired over 

a hard, irregular water bottom are contaminated by 

strong multiple-interference and side-scatter noise that 

dominates the shot gathers and conventionally stacked 

data. These strong coherent noises combine not only to 

mask shallow subsurface reflections, but also to make it 

extremely difficult to analyze weak reflections from the 

lower crust and upper mantle. Thus, to perform a 

geologically sound interpretation and to properly migrate 

deep reflections, multichannel, pre-stack processing 

techniques based on the moveout differences between 

signal and noise are required. 

In 1986, as a part of the Great Lakes International 

Multidisciplinary Program of Crust Evolution 

(GLIMPCE), more than 1,400 km of deep crustal 

reflection profiles were acquired in the Great Lakes 

region. The energy source was a 130 L (7,800 in.3

) tuned 

airgun array; 20 seconds of data were recorded at each 

shot point. Preliminary stacked sections were dominated 

by the coherent multiple and side-scatter noises. Poststack dip filtering suppressed strong side-scatter noise of 

low apparent velocity, but it did not enhance the 

subsurface reflections as desired. Predictive deconvolu-
tion suppressed the short-period reverberations caused 

by source and receiver ghosts, but it could not adequately 

handle the long-period (on the order of 400 ms) 

multiples. Therefore, dip filtering in the shot domain was 

applied in order to suppress the side-scattering noise, and 

time-variant dip filtering in the CDP domain was 

performed in order to reduce the water-bottom multiple 

interference. 

These pre-stack processing techniques were highly 

successful in reducing the coherent noise in the 

GLIMPCE seismic data. A post-stack, signalenhancement technique based on the strength of the 

reflected energy provided additional enhancement in the 

deep reflectors. Examples of banded Moho reflections 

around 12-14 seconds and of the Keweenawan rift basin 

within Lake Superior demonstrate the effectiveness of 

these seismic data processing techniques. 

Implications of Trace-Element 

Concentrations in Modern Tree Fern 

Tissues for the Origin of Elements in 

Vitrinites of the Pittsburgh Coal Bed 

Paul C. Lyons and Curtis A. Palmer 

Tissues from the modern tree fern Alsophila 

tricolor and vitrinite concentrates from the Pittsburgh 

coal bed (which is known to be vitrinite rich and derived 

from mainly tree fern species) were analyzed for 21 

elements (fig. 1) by instrumental neutron activation 

analysis. The following maceral precursors are suggested 

for the tissues analyzed: telinite (xylem), collinite 

(parenchyma), and telinite (sclerenchyma). As compared 

to the Pittsburgh coal vitrinites (fig. 1 ), contents of the 

alkali metals (Na, K, Cs) and alkaline earths (Ca, Ba) are 

higher in all fern tissues analyzed; the reverse is true for 

AI. As compared to trunk sclerenchyma, the root sclerenchyma has similar or greater concentrations of all 

elements and the root parenchyma has concentrated 

most elements when compared to both trunk and root 

sclerenchyma; the xylem has the highest concentrations 

of Sc, Mn, Sm, and Zn but the lowest concentrations of 

AI when compared to other tissues (fig. 1 ). Cl is similar 

in concentration in all tissues analyzed. 

The results indicate a primary concentration of 

almost all elements by histological fractionation in the 

tree fern and the reprecipitation of AI and its fixation in 

clays or other aluminum forms in the vitrinite. Because 

the parenchyma is the most degradable of all the tissues 

in the tree fern, it is a good potential source of metals 

mobilized during degradation and fixed in other forms. 

However, the relatively high concentrations of alkali 

metals and alkaline earths in all tissues, as compared to 

29 

those in the Pittsburgh coal vitrinites, indicate probable 

substantial loss of these elements from the peat-coal 

system by dewatering and other processes. The xylem is a 

good potential source of Zn and rare earths in the 

Pittsburgh coal. 

Basin Analysis Studies of 

Cambrian through Mississippian 

Rocks, Powder River Basin, 

Wyoming and Montana 

David L. Macke 

The Cambrian through Mississippian sedimentary 

rocks of the Powder River Basin represent nearly half of 

Phanerozoic time, yet they remain virtually unexplored 

for petroleum in the subsurface. The lack of an economic 

reason to study these rocks has hampered the 

development of precise depositional models for these 

sequences, as have the depth of prospective beds and 

some longstanding misconceptions about the regional 

stratigraphy. 

Rocks of the same age range in the Bighorn and 

Williston Basins and in the Central Montana trough have 

produced much oil and gas, as have the overlying 

Pennsylvanian strata of the Powder River Basin. A 

synthesis of published stratigraphic information, together 

with a regional analysis of sedimentary sequences, has 

been undertaken to evaluate the economic potential of 

the pre-Pennsylvanian Paleozoic formations in the 

Powder River Basin. 

Stratigraphic studies have documented a 

succession of marine transgressions and regressions on 

the flanks of a land area in southeastern Wyoming. 

Through most of early Paleozoic time, the land area 

persisted as a subdued geographic feature; at the end of 

the Mississippian, it rose. Erosion during episodes of 

marine regression, especially during Late Silurian and 

Devonian, has removed much of the depositional record 

in the area; but onlap can be demonstrated with relative 

certainty for Ordovician and Devonian into Mississippian 

age. 

The repetition of sedimentological features in the 

rock record indicates persistent geologic controls in the 

region, and suggests that the paleoenvironments might 

have provided targets for exploration. 

The Petroleum System-A Classification 

Scheme for Research and 

Resource Assessment 

Leslie B. Magoon 

A petroleum system includes those elements that 

are essential for an oil and gas deposit to exist in nature. 
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r 0.01l_~_j--~_l __ L_j_~ __ j__L __ L_~_j--~_l __ L_JL~--j_-===c===_j--~_l __ L__L~L_j_~ __ l__L~L_~~==~~==~::::~::::~ Figure 1. Comparison of trace-element concentrations in vitrinites of the Pittsburgh coal bed with those of tissues in the modern tree fern Alsophi/a tricolor. Values are 

normalized to the maximum concentrations in the vitrinites of the Pittsburgh coal bed. Tail of arrows indicates maximum or minimum values of upper or lower limits, 

respectively, of the ratio of elemental concentration in tissue over maximum elemental concentration in Pittsburgh vitrinites. Patterned dots with arrows indicate single 

ratios only, rather than two or three ratios as represented by columns. 

@ ® e Single points 
The basic elements include a petroleum source rock, 

migration path, reservoir rock, seal, and trap. All these 

elements must be correctly placed in time and space for 

a petroleum deposit to occur. The stratigraphic, areal, 

and temporal extent of the petroleum system is specific. 

Stratigraphically, the system is limited to the following 

rock units: petroleum source rock, rocks through which 

migration occurred, reservoir rock (trap) and rock overburden 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) that emanated from 

that source. The temporal extent of the system is that 

span of geologic time beginning with deposition of the 

source rock to the time of latest petroleum migration. 

A petroleum system can be identified in terms of 

geochemical correlation of oils and source rocks at three 

levels of certainty: known(!), hypothetical(.), or 

speculative(?). A known identification includes those 

petroleum systems where successful oil-source rock 

correlations are obtained. A hypothetical identification 

includes those petroleum systems where oil or gas 

deposits can be shown to be genetically related, and 

source rocks can be geochemically documented, but no 

geochemical correlation exists. A speculative 

identification includes those petroleum systems where 

only geologic evidence supports a relationship between 

the petroleum deposit and its source rock. I propose that 

the petroleum system designation include the name of 

the source rock, followed by the name of the major 

reservoir rock and a symbol expressing the level of 

certainty, for example, the Beluga-Sterling(.). 

After a petroleum system is identified, named, and 

its level of certainty established, it must be classified. The 

classification scheme is based on the reservoir rock type 

(siliciclastic or carbonate), source rock kerogen type (I, 

II, or III), and as either a purebred or a hybrid system. 

This scheme allows for 12 separate categories of 

petroleum systems. A purebred petroleum system is one 

whose elements were formed in a single sedimentary 

basin during a single tectonic cycle, whereas a hybrid 

petroleum system is one whose elements formed in at 

least two superimposed sedimentary basins and tectonic 

cycles. In Alaska's Cook Inlet basin, for example, the 

Beluga-Sterling(.) petroleum system, a series of biogenic 

gas deposits, is a purebred system, because the source 

and reservoir rocks were deposited in a single 

sedimentary cycle; the Tuxedni-Hemlock(.) petroleum 

system is a hybrid system, because the Jurassic source 

rock was deposited in a forearc marine basin and 

separated by a regional angular unconformity from the 

Tertiary reservoir rock and overburden, which were 

deposited in a nonmarine basin. 

31 

USGS geologists have classified the petroleum 

systems in the United States. As we classify the Nation's 

petroleum systems using these criteria, we may clearly 

identify the various elements of each system, and then 

compare across systems to generalize the mechanism and 

capacity to generate, migrate, and trap hydrocarbons. 

Plans call for selected petroleum systems to be 

researched and assessed; among the first studied will be 

a petroleum system on the North Slope of Alaska. 

Estimates of Undiscovered Recoverable 

Oil and Gas Resources for the 

Onshore and State Offshore 

Areas of the United States 

R.F. Mast, G.L. Dolton, R.A. Crovelli, R.B. Powers, 

R.R. Charpentier, D.H. Root, and E.D. Attanasi 

How much oil and gas remains to be discovered in 

the United States is an important question as well as a 

subject of controversy. The U.S. Geological Survey has 

published estimates over the years; this report presents a 

new assessment. Estimates of undiscovered recoverable 

conventional oil and gas resources were made for more 

than 240 geologically defined plays in 80 petroleum 

provinces covering the onshore and the State offshore 

areas of the conterminous 48 States and Alaska. The 

methodology developed was flexible and handled the 

variety of play situations encountered. The results can be 

described not only in terms of total volumes of oil and gas 

but also in terms of geologic setting, accumulation size, 

and number of accumulations. 

The plays were developed by geologists for each 

petroleum province. Geologic, geochemical, and geophysical data were used to define and bound each play and to 

provide a basis for assessment. Resource estimates for 

undiscovered accumulations with recoveries larger than 

1 million barrels of oil or 6 billion cubic feet of gas were 

made using a play analysis method that required 

estimation of play and accumulation favorability or risk, 

the size distribution of undiscovered recoverable 

accumulations, and the distribution of the number of 

undiscovered accumulations. Size data from either 

discovered accumulations in each play or from an analog 

play were employed to estimate the size of undiscovered 

accumulations. Curves were fit to the size data for the 

discovered accumulations which were generally split into 
three sequential parts: the first, second, and last 1/3 of 

the accumulations discovered in each play. Parameters 

from these fitted curves provided a basis for estimating 

the size distributions for the undiscovered resources. The 

numbers of undiscovered accumulations greater than the 

minimum sizes were estimated, utilizing play maps 

showing well penetrations and the areal sizes of the oil 

and gas accumulations, along with the drilling history. 

Finally, ratios of associated-dissolved gas-to-oil and 

condensate-to-gas were estimated. All these 

approximations were used to calculate the probabilistic 

estimates of conventional recoverable oil, gas, and 

natural gas liquids in accumulations greater than the 

cut -off values. The play analysis methodology used to 

compute these estimates is an analytical method derived 

from probability theory as opposed to Monte Carlo 

simulation. 

Undiscovered recoverable resources in fields 

smaller than the cut-offs of 1 million barrels and 6 billion 

cubic feet were estimated for each province. Statistical 

extrapolation from the numbers of fields in field-size 

classes greater than the cut-offs produced estimates of 

the numbers of fields in field-size classes below the 

cut-offs. The number of small fields already discovered 

and the volume of oil and gas in these fields were also 

utilized to estimate the undiscovered resources in small 

fields. 

Economically recoverable resources were 

determined by applying minimum economic sizes to play 

estimates and estimating the percentage of the smallfield resources thought to be economic. In general these 

percentage estimates were based on the nature of the 

plays in the province and the estimated depth of these 

undiscovered resources. 

Province level results were formed by aggregating 

the play estimates and the small-field estimates for both 

undiscovered recoverable and economically recoverable 

undiscovered resources. Regional and National level 

results were developed by aggregating province and 

region results respectively. 

The results of the assessment are tabulated below. 

The resource estimates are smaller than those published 

by the U.S. Geological Survey in 1981. However, the data 

used were somewhat different because the method 

employed was different. Some of the resources classified 

as undiscovered in 1981 are now classified as identified, 

unconventional or inferred resources; and the resources 

discovered from 1981 to 1986, especially in some onshore 

frontier areas, were disappointing in view of the very 

large exploration drilling effort expended. 

32 

Undiscovered conventional resources 

[fCF, trillion cubic feet] 

Associateddissolved 

gas TCF 

Mean F95 F5 Mean 

Total 

Lower 48 

Alaska 

Total 

Lower 48 

Alaska 

Crude oil 

Billions of 

barrels 

Non-associated 

gas TCF 

F95 F5 Mean F95 F5 

R~overable resources 

19.6 51.9 33.4 141.0 295.0 209.2 

15.8 25.2 20.2 124.5 204.4 161.3 

3.6 31.3 13.2 10.8 122.8 47.9 

31.0 

26.4 

2.6 

Economically recoverable resources 

14.0 42.0 25.7 118.5 199.3 155.6 24.7 

14.4 23.7 18.7 117.6 198.2 154.6 24.5 

0.9 21.0 6.9 0.1 3.2 1.0 0.0 

U.S. Energy Supply from the 

61.9 44.8 

44.6 34.8 

24.5 10.0 

42.9 33.0 

42.7 32.9 

0.4 0.2 

Perspective of World Petroleum Geology 

Charles D. Masters 

The purposes of the World Energy Resources 

Program assessment are to quantify the regional 

distribution and potential for the occurrence of 

petroleum resources worldwide, and to establish a baseline of world petroleum geology knowledge that will 

permit the early recognition of anomalous exploration 

results that might affect assessment. When the program 

began, the available data base was the geologic literature 

of the world and a country-level understanding of 

cumulative production and reserves. Given the required 

time frame of response and our personnel resources, 

assessment methods had to parallel those of the domestic 

petroleum assessments conducted by the USGS and 

published in 1975 and 1981-that is, a modified delphi 

procedure. The principal means to develop scaling 

factors for the subjective assessment included regional 

finding-rate projections, volumetric calculations from 

basin analog determinations, and locally discrete play 

analysis reservoir calculations. With developing program 

maturity, the geologic and reserves data bases have 

expanded to play-level understanding in many basins, and 

field reserves data can now account for the occurrence of 

more than 90 percent of world reserves. This expanded 

data set offers the possibility of selected field-size 

distribution assessment analysis and certainly more 

sophisticated finding-rate studies by field-size class. In 

addition, we are continuing to develop regional 

understanding of remote areas such as the Arctic and the 

Antarctic, as well as the occurrence of petroleum as it 

relates to paleotectonic plate positions and to principal 

zones of source rock occurrence. We are also 

investigating the occurrence of condensate, to improve 

our ability to assess its resource potential. 
Results of our program studies indicate that 

petroleum occurs in such large quantities as to yield a 

barrels-of-oil-equivalent (BOE) reserve-to-production 

ratio of 50. Though the quantity is large, the distribution 

of discovered conventional petroleum is narrow, and our 

assessment identifies no new areas that might 

significantly alter that distribution. On the other hand, a 

very large recoverable unconventional resource of extra 

heavy oil and bitumen, of comparable dimension to the 

Middle East conventional oil, exists in Venezuela and 

Canada. This resource could provide a Western 

Hemisphere counterbalance to Middle East resource 

dominance. Though conventional resources are narrowly 

distributed, present-day oil production is not, with only 

31 percent deriving from OPEC, 38 percent from the 

United States and the U.S.S.R., and the remaining 31 

percent from more than 60 individual countries. A key to 

near-term energy security lies in maintaining diversified 

sources of conventional petroleum supply until such time 

as the unconventional oils can find their place in the 

market, along with a greatly expanded use of coal. 

Seismic Stratigraphy of the 

Bakes Basin, Southeastern Hungary 

Robert E. Mattick, Janos Rumpler, Antal Ujfalusy, 

Bela Szanyi, and lren Nagy 

The Bekes basin, a subbasin of the Pannonian 

Basin, is located in southeastern Hungary, covers an area 

of about 3,000 square kilometers, and contains Neogene 

and younger lacustrine sedimentary rocks that locally are 

in excess of 7,000 meters thick. Successful hydrocarbon 

exploration in the Bekes basin and surrounding areas 

began in the early 1960's, and as a result of extensive 

exploration since that time, all of the major structures 

and most of the minor structures have been located and 

drilled. In an effort to begin a systematic search for subtle 

traps, the USGS and the Hungarian Oil and Gas Trust 

jointly completed a basin analysis study of the Bekes 

basin. The results of seismic stratigraphic study are 

summarized herein. 

The Neogene history of the Bekes basin reflects 

one of the last episodes of infill of the much larger 

Pannonian Basin. It was not until other subbasins to the 

northwest, north, and northeast became filled by 

southward progradation of massive sediment wedges that 

the major river systems which transported sediments 

were able to advance to the area of the Bekes basin. 

Thereafter, rapid deltaic infilling of the Bekes basin 

proceeded as major river systems converged and lacustrine sedimentation became confined to an increasingly 

small basin. 

33 

Post-rift infilling of the Bekes basin reflects 

gradually shallowing water conditions. This shallowing 

resulted from sedimentation rates that were higher than 

basin subsidence rates. Initial water depths in the basin 

were about 1,500 m, but the last sequences of welldeveloped deltaic wedges were deposited in water depths 

of 200-400 m. 

On seismic records, three sedimentary rock units 

can be mapped. From oldest to youngest they are: (1) a 

basal marl and turbidite sequence; (2) a prograding 

sequence that represents an episode of delta 

construction; and (3) an uppermost unit which 

represents delta plain facies in which depositional 

environments varied from shallow lake, fluvial, and 

marsh to terrestrial soils. 

The basal turbidite sequence in the southern part 

of the basin is inferred to consist of distal turbidites. To 

the north, however, this unit consists of more proximal 

turbidites. 

During much of the early history of the Bekes 

basin, large volumes of clastics, transported by rivers, 

were channeled along structural depressions; these 

troughs were derived from pre-rift or early rift 

topography of the basin. Along the northern margins, 

sediments were transported basinward through subaqueous structural depressions, and in some of these areas, 

large subaqueous fans- a few possibly containing coarsegrained sandstones-are well developed near the base of 

the slope. 

In later stages of basin infill, sand was derived 

primarily from the upper part of the prograding delta 

slope and moved downslope by slumping, sliding, mass 

flow, and turbidity currents. In this later stage, subaqueous fan systems and channels on the slope were poorly 

developed. 

Rates of deposition are calculated to be 200-310 

m/million years for the basal turbidite sequence, 1,000 

m/million years for the prograding sequence, and 500 

m/million years for the uppermost sequence. 

A strong unconformity mapped on seismic records 

in the southeastern part of the Bekes basin is interpreted 

as representing massive, subaqueous scour that occurred 

during the Neogene as waters of the Pannonian lake 

flowed eastward out of the basin. 

Effects of Climate, Tectonism, and 

Variations in Sea Level on the 

Formation of the Cretaceous Coals of 

North America 

Peter J. McCabe, Michael E. Brownfield, Dan E. 

Hansen, Robert D. Hettinger, Mark A. 

Kirschbaum, and J. David Sanchez 

Extensive deposits of Cretaceous coal-bearing 
strata are present in western North America, extending 

from the North Slope of Alaska to northern Mexico. 

Most of the Cretaceous sediments were derived from the 

active Cordillera region and were deposited in foreland 

basins on the western margin of the Western Interior 

seaway. A multidisciplinary study is in progress to 

document, and attempt to explain, the temporal and 

spatial distribution of the Cretaceous coals. The study 

examines the effects of variations of paleoclimate, 

tectonics, and relative sea level on a continent-wide scale. 

In addition, coal quality is related to the regional 

depositional settings. 

Many aspects of coal quality (for example, maceral 

composition, ash content, sulfur content) are determined 

by the flora and the hydrology of the mire in which the 

original peat accumulated. The existence of Cretaceous 

coals throughout the length of the Western Cordillera 

provides a unique opportunity to determine variations in 

mire type with climate over a range of 50° of paleolatitude, and to examine the effects of these variations on 

coal quality. The relationships between coal beds and 

associated clastic facies should also be expected to 

change with varying mire types. 

Recent developments in our understanding of foreland basin evolution, Cretaceous sea-level changes, and 

peat-forming environments make this an optimal time to 

commence a regional synthesis of North America's 

Cretaceous coals. Results of this study should aid the 

development of better predictive models of coal quality 

and seam thickness. These models will take into account 

the effects of major controls on sedimentation (climate, 

tectonics, sea-level changes) rather than just the local 

depositional environment. Many of the major coal 

deposits of the world lie within foreland basins, and it is 

hoped that the models derived from this study will be 

transferable to coal deposits of differing age in other 

areas. 

Offshore Resource Geology of 

Central California 

David S. McCulloch and Stephen D. Lewis 

The hydrocarbon resource potential of offshore 

central California ultimately resides in shelf and slope 

basins, and possibly in adjacent large deep-sea fans. 

However, with present water-depth limited technology, 

thin near-shore late Tertiary shelf basins are the principal 

exploration targets. Although they rest on a variety of yet 

ill-defined accreted basement blocks, these shelf basins 

34 

have generally similar late Neogene structural and stratigraphic histories. These histories suggest that the 

continental margin was emergent and that erosion 

generally extended to Cretaceous basement during the 

global Oligocene low sea level. At about the OligoceneMiocene boundary (23 Ma ), a possible change in PacificNorth American plate motion may have accounted for 

the start of transtension that was manifested along the 

margin by subsidence and marine volcanism, and in some 

basins, by the initiation of transtensional basement 

structures. Structural growth continued in the Miocene 

as expressed by relative subsidence of the basins and 

elevation of partially fault controlled elongate structural 

highs along the outer edge of the shelf. Subsidence was 

accompanied by deposition of silica-rich hemipelagic 

strata (Monterey Formation equivalent) at bathyal and 

mid-bathyal depths. 

Transtension was replaced by transpression at 

about the time (=3-5 Ma) of a change in relative 

Pacific-North American plate motion, and terrestrially 

derived sediment that flooded into the shelf basins 

probably reflects coastal uplift. Transpression was 

accompanied by the growth of generally coast-parallel 

folds and compressional faults. In some basins earlier 

transtensional basement structures localized the younger 

folds and compressional faults. Large vertical-separation 

faults along basin boundaries were structurally 

overprinted by compression, giving them the appearance 

of high-angle reverse and thrust faults. Shallow Holocene 

basins that developed on the shelf, folded and faulted 

sea-floor strata, and compressional and right-slip 

earthquake focal mechanisms indicate continuing transpression on the shelf. 

Monterey rocks (chert, porcellanite, siliceous 

shale) originally deposited as biogenous silica, fine terrigenous debris, and organic matter are the primary 

exploration targets. These rocks were commonly 

encountered along most of the offshore margin in a 

1960's round of exploratory drilling, but because of a 

poor onshore production history, they were untested 

despite encouraging hydrocarbon shows. Recent 

experience onshore and offshore has shown comparable 

strata to be producible, primarily from fracture 

reservoirs; and recently developed fields in the 

southernmost basin (including a giant and several 

smaller fields in offshore Santa Maria basin) have 

developed production from these strata. The 

combination of late Neogene structures, formation 

brittleness enhanced by diagenetic silica alteration, and 

hydrocarbon generation at moderate temperatures and 

shallow burial depths makes these strata attractive 

exploration targets. 
Interpretation of Seafloor 

Processes in the 

Gulf of Mexico Using the 

GLORIA Sidescan Sonar System 

Bonnie A. McGregor and David C. Twichell 

GLORIA sidescan-sonar images provide a unique 

view of the seafloor in the deep water of the Gulf of 

Mexico. A better understanding of the morphology, 

surficial geology, and sedimentary processes of the 

continental slope and rise in the Gulf of Mexico is 

important for evaluating and developing energy and 

mineral resources, and for siting seafloor structures. The 

GLORIA data provide information on depositional 

environments and geologic processes that is important in 

developing depositional models useful as analogs in 

understanding the rock record. 

The EEZ in the Gulf of Mexico can be divided into 

three major provinces: a salt deformation province in the 

western section, the Mississippi Canyon and Fan system 

in the central section, and a carbonate province in the 

eastern section, which is separated from the terrigenous 

Mississippi Fan by the Florida Escarpment. 

In the western gulf, the most striking feature on the 

imagery is the Sigsbee Escarpment, which marks the 

seaward edge of the salt deformation province. Vertical 

relief on the escarpment is approximately 500 m, and 

piles of debris along the base are visible on the sonographs, suggesting that sediment is eroded from the 

escarpment. Seaward of the escarpment, patches of seafloor with numerous lineations are interpreted as bedform fields formed by the reworking of debris from the 

escarpment. Landward of the escarpment, the 

continental slope has a very complex morphology, 

formed in response to intrusion by the salt. 

The Mississippi Canyon and Fan system is the 

dominant feature in the central gulf. The Mississippi 

Canyon on the slope and upper fan contains debris-flow 

deposits, and the flows have spilled over the canyon walls 

at meanders. As the filled Mississippi Canyon is traced 

seaward onto the middle part of the Mississippi Fan, a 

meandering channel becomes apparent. Adjacent to this 

channel on the eastern fan, the seafloor is marked by very 

intricate flow patterns. This region is interpreted to 

contain debris-flow deposits emanating from the 

Mississippi Canyon and covering most of the fan. 

In the northeastern gulf, a submarine debris-flow 

deposit is present near the mouth of DeSoto Canyon. A 

meandering channel partially buried by the deposits 

emerges and trends southward, parallel to the Florida 

Escarpment. Another channel (perhaps abandoned) lies 

35 

closer to the base of the escarpment, and a tongue of the 

debris-flow deposits from DeSoto Canyon fills the 

channel. 

The dominant feature in the eastern gulf is the 

Florida Escarpment, which has a gradient of as much as 

40° and relief ranging from 1,000 m in the north near 

DeSoto Canyon to 2,500 m west of the Florida Keys. 

Numerous scarps having up to 250m of relief are present 

in the Tertiary carbonate sediments above and landward 

of the escarpment. These scarps are the product of mass 

wasting, and some align with canyons that dissect the 

escarpment. The canyons appear to be conduits for 

massive slumps of the Tertiary sequence, resulting in the 

deposition of carbonate material in the deep water of the 

gulf, interbedded with clastic material of the Mississippi 

Fan. 

The GLORIA mosaic demonstrates that mass 

wasting is much more extensive in the Gulf of Mexico 

than previously thought, that it exhibits a variety of styles 

and volumes, and that it has been a major process in the 

distribution of sediments in the deep water of the Gulf of 

Mexico. Four submarine channels can also be identified 

meandering across the floor of the gulf, providing 

pathways for the transportation and distribution of 

sediments in deep water. 

The Distribution of 

Rare-Earth Elements in the 

Pittsburgh Coal Bed 

James S. Mee, Curtis A. Palmer, and 

Charles L. Oman 

It has been generally believed that the rare-earth 

element (REE) distribution in coals is similar to that of 

shale. To examine this hypothesis further, 114 coal 

samples ( < 30 percent ash) from the Pittsburgh coal bed 

in Pennsylvania, West Virginia, and Ohio were analyzed 

by INAA for the REE (La, Ce, Sm, Eu, Tb, Yb, and Lu ). 

These samples were normalized to the North American 

Composite Shale, NACS, as explained in a 1968 study by 

L.A. Haskins and others, to better illustrate the 

differences in the REE concentration between the coals 

studied and to provide a better understanding of the 

conditions of formation and the migration of REE 

through the coal bed. 

The slope of the REE pattern may be used to 

determine the relationship between the REE pattern of 

NACS and sample coals. The comparison of the ratio of 

the light REE (LREE-La, Ce, Sm) and the heavy REE 

(HREE-Tb, Yb, Lu) can be estimated as a La:Lu ratio. 
LA CE PR ND PM SM EU GD TB DY HO ER TM YB LU 

0.25 

0.20 

0.15 

0..10 

• SOUTHERN COAL 

o NORTHERN COAL 

Figure 1. The northern coal is representative of a "flat" rare-earth pattern, taken from the northern field of the Pittsburgh coal 

bed. The southern coal is representative of the majority of the coals in the Pittsburgh coal bed, which have a Eu anomaly. 

The samples studied have an average La:Lu of 

approximately 1, confirming the similarity of the REE 

pattern to that of shale. 

The Eu abundances of the coal samples, however, 

show a distinct difference in the samples depending upon 

the locality in the coal beds. The extent of the difference 

(Eu anomaly) may be measured by Eu:Eu *, where Eu is 

the actual normalized concentration of europium and 

Eu * is the "expected" value by interpolation between Sm 

and Tb. Only the coals from the northern part of the coal 

bed, north of lat 40° N., which represent less than 15 

percent of the coal bed, have REE patterns that are 

similar to the NACS, Eu:Eu*= 1, which demonstrates 

similarities to the REE patterns of the NACS. A majority 

of the coals south of lat 40° N. have Eu:Eu * ratios that 

range from 0.8 to 0.5 (fig. 1 ). 

The differences between the northern and 

southern coals may be due to several environmental 

conditions. The climatic differences in the swamp and a 

slower burial rate may have prevented Eu + 2 from 

forming in the northern section. The Eu anomalies, 

present in the REE patterns of the southern coals, are 

probably a result of Eu + 3 being reduced to Eu + 2 due to 

the conditions present during early diagenesis, for 

example, rapid burial and differences in eH and pH. 

36 

Seismic Reflection Profiles Across the 

Eastern Bighorn Mountains 

Between Buffalo and Story, Wyoming 

John J. Miller, Myung W. Lee, John A. Grow, E.N. 

Hinrichs, and S. L. Robbins 

Two multichannel seismic reflection lines west of 

Story and Buffalo, Wyoming, were obtained (courtesy of 

Chevron U.S.A., Inc.) and reprocessed by the USGS. 

The data were recorded using portable equipment having 

a dynamite energy source, 120 channels per shot, 6-

second record length, 2-ms sample interval, and 

geometry affording 15-fold subsurface coverage. 

Reprocessing was accomplished using the USGSowned DISCO seismic data-processing system software. 

The data were processed to the stage of unmigrated stack 

using a standard processing sequence that included prestack deconvolution and two iterations of residual statics 

calculations. Datum and residual static calculations were 

problematic because the near-surface velocity varied 

abruptly due to an outcrop of overthrust granite. Special 

attention was therefore given to these processing steps. 

Wave equation migration applied after stacking used a 

velocity model determined from a series of constantvelocity migration tests. The velocity model developed to 

convert the data to depth integrated velocities 
determined from closely spaced stacking velocity 

analyses with acoustic logs from nearby boreholes. 

After reprocessing, these two lines clearly show 

sub thrust sedimentary rocks of Paleozoic through Paleocene age overthrust by Precambrian granites and 

gneisses. A reflection from the thrust fault plane dipping 

30° W. is imaged. The Buffalo Deep fault, a high-angle 

reverse fault in the sedimentary rock sequence, appears 

at the eastern end of both lines. 

Stratigraphic Framework of the 

Pannonian Sequence (Neogene), 

Bekes Basin, Southeast Hungary 

C.M. Molenaar, I. Revesz,1 1. Berczi, 1 A. Kovacs, 1 

Gy. K. Juhasz,1 I. Gajdos, and B. Szanyi1 

The Bekes basin, a sub-basin of the Pannonian 

basin in southeastern Hungary, is a late Tertiary 

structural basin that was filled by as much as 6,500 m of 

Neogene sandstone, siltstone, claystone, and marl. These 

rocks, known as the Pannonian sequence or group, are oil 

and gas productive in structural traps around the flanks 

of the basin. Because of rapid depositional rates and the 

lacustrine depositional environment, biostratigraphic 

zones within the thick sequence are lacking. The large 

amount of good multichannel CDP seismic data, 

however, provides a good method of establishing time 

correlations between wells and provides information on 

depositional environments. In general, the seismic facies 

patterns correspond to the depositional environments, 

which in turn reflects established formational or lithogenetic terminologies. 

Well-log cross sections correlated with seismic data 

indicate that the Pannonian sequence was deposited in a 

wide range of depositional environments, ranging from 

deep basinal lacustrine to basin slope to shallow lake and 

delta plain to alluvial plain. Essentially one depositional 

cycle is represented and the facies are highly diachronous. The basinal facies consist of a basal distal clay marl 

unit overlain by turbidites containing thick amalgamated 

sandstone beds. The slope facies consist of clay marls or 

shales, turbidites, and slump deposits that grade upward 

into predominantly clay marls. The shallow-lake, deltaplain, and alluvial-plain facies consist of interbedded 

sandstone and clay marl and (or) lignitic shale. 

The relief of the slope or clinoform beds indicates 

that basinal beds were deposited in water depths greater 

than 500 m. Depositional dips of the slope facies beneath 

a conspicuous shelf break were at least 3°-5°. 

1

Hungarian Oil and Gas Trust, Budapest, Hungary. 

37 

Peat Deposits on Coastal SumatraA Modern Analog of Coal Formation 

Sandra G. Neuzil, C. Blaine Cecil, Supardi1

, A.D. 

Soebakty1 , Cortland F. Eble, Christopher Wnuk, 

and Lim Meng Sze Wu2 

Detailed study of modern peat deposits may be 

used to develop predictive models for the occurrence and 

quality of coal. Modern peat deposits on coastal Sumatra 

appear to be an excellent analog for low-ash and lowsulfur coal beds that are inferred to be derived from peat 

that formed in a tropical environment. These modern 

tropical peat deposits are areally extensive, thick, domed, 

rainfall dominated (ombrogenous), low in ash ( < 10 

percent) and sulfur ( < 1 percent) contents, and acidic 

(pH 3-6). 

Field studies were conducted in the Siak Kanan 

and Bengkalis peat deposits in Riau Province, Sumatra. 

The Siak Kanan peat deposit is the northern part of a 

large peat swamp that is bounded on the northwest by the 

Siak River, on the northeast by Panjang Strait, and on the 

south by the Kampar River. It is on the coastal plain and 

contains 1,100 km2 of peat >1m thick (13.5 m maximum 

thickness). The Bengkalis peat deposit covers most of 

Bengkalis Island, located 10 km off the coast of Sumatra, 

and contains 700 km2 of peat > 1 m thick (10 m 

maximum thickness). The surface topography of each 

peat deposit shows several more or less coalesced peat 

domes with radial drainage out from the center. Tidal 

creeks receive drainage from the margins of both peat 

deposits where they are bordered by straits and estuaries. 

Because the base of the peat is generally at or slightly 

above high tide, the composition of the peat is unaffected 

by external sediments and marine or estuarine water. 

Annual rainfall in this region of Sumatra is >2.5 

m; rains are frequent throughout the year. Precipitation 

exceeds evapotranspiration, and the excess water from 

rainfall drains off and percolates through the peat domes. 

The absence of clastic sediment influx and the low 

concentration of dissolved solids input to the peat via 

rainfall result in the formation of low-ash peat. The 

dominant source of ash in the peat is the inorganic 

constituents concentrated by the plants. Our preliminary 

data show a relative increase in the ash content at the top, 

bottom, and margins of the peat deposits. Because of 

rainwater flushing, both peat deposits have a low-sulfur 

content even where they are adjacent to a marine 

environment. The ash and sulfur distribution in the peat 

is comparable to that of many coal beds. 

1

Directorate of Mineral Resources, Bandung, Indonesia. 2P.T. Utah Indonesia, Jakarta, Indonesia. 
The acidity of the peat deposits restricts microbial 

degradation of the peat. The acidity decreases with depth 

from pH 3 in surface peat to pH 3-5 in basal peat in Siak 

Kanan and pH 4-6 in Bengkalis. Methane and possibly 

hydrogen sulfide were detected in some basal peats and 

in some sediments directly below the peat, especially in 

the Bengkalis peat deposit. This indicates that anaerobic 

methanogenic and sulfate reducing bacteria are active in 

the less acid basal peat and (or) in the organic-rich 

sediments below the peat. Preservation of some plant 

parts is excellent and hard wood is often encountered in 

the peat. The peat is predominantly fibric to fibric/hemic 

in texture. Highly decomposed sapric peat is uncommon 

and generally restricted to the base of the deposit. Peat 

accumulation rates are rapid, 4 m in =900 yr has been 

measured in the lower part of the peat profile in central 

Siak Kanan, indicating restricted degradation of the plant 

litter. Field observations indicate that facies exist within 

the peat deposits, and that these may be analogous to 

facies in coal deposits. 

Domed tropical ombrogenous peat deposits, such 

as Siak Kanan and Bengkalis, may represent a type of 

modern analog for coal deposits that are characterized by 

low-ash and low-sulfur contents and are inferred to have 

originated in a tropical climate. 

Estimation of Paleogeothermal 

Gradients and their Relationship to the 

Timing of Petroleum Generation, 

Eagle Basin, Northwestern Colorado 

Vito F. Nuccio, Christopher J. Schenk, and 

Samuel Y. Johnson 

Estimates of paleogeothermal gradients have been 

developed for three locations in the Eagle basin, 

northwestern Colorado, and the proposed timing of 

petroleum generation from an organic-rich source rock, 

the Belden Formation (Early and Middle Pennsylvanian) 

proposed. Levels of thermal maturity were determined 

by vitrinite reflectance (Rm) and calibrated with the 

Lopatin Time Temperature Index (TTl) modeling to 

determine paleogeothermal gradients. Different paleogeothermal gradient scenarios were used for each 

location, and "best fit" gradients which match TTl values 

with Rm values were determined. 

The burial histories for the three localities are 

quite different, because during Pennsylvanian deposition, 

38 

the three localities were in separate subbasins. Also, 

because of the variations in thickness of the overlying 

strata the thermal maturity ranges from 2.50 percent at 

two ~f the locations to 3.70 percent Rm at the third. 

Depth of burial is not the only factor controlling the 

thermal maturity: geothermal gradients also differ for the 

three locations. 

At one locality (Gilman), two paleogeothermal 

gradient scenarios have been postulated. The first 

scenario assumes a constant geothermal gradient of 1.80 

°F/100 ft (32.9 °C/km) through time. In this case, the 

Belden Formation enters the oil window 275 Ma and 

leaves it 205 Ma. The second scenario assumes a 

changing paleogeothermal gradient; 2.30 °F/100 ft ( 42 

°C/km) from 320 to 265 Ma, and 1.70 °F/100 ft (31.2 

°C/km) from 265 Ma to present. Using this model, the 

Belden entered the oil window 284 Ma and left it 263 Ma. 

Both these models match the 3.70 percent Rm measured 

at Gilman with the corresponding TTl value of between 

40,000 and 50,000. 

At a second locality (Sweetwater), two models 

were used. The first assumes a constant gradient of 1.78 

°F/100 ft (32.4 °C/km) through time and puts the oil 

window between 195 and 77 Ma. The second model 

assumes a gradient of 2.10 °F/100 ft (38.4 °C/km) from 

320 to 265 Ma and a gradient of 1.70 °F/100 ft (31 °C/km) 

from 265 Ma to present, placing the oil window between 

230 and 73 Ma. These models match the 2.50 percent Rm 

with the corresponding TTl value of approximately 

2,700. 

For a third locality (Glenwood), two models were 

again used. The first assumes a constant gradient of 1.87 

°F/100 ft (34.0 °C/km) through time and puts the oil 

window between 168 and 75 Ma. The second scenario 

assumes a gradient of 2.60 °F/100 ft (47.4 °C/km) from 

320 to 265 Ma and a gradient of 1.70 °F/100 ft (31.0 

°C/km) from 265 Ma to present, placing the oil window 

between 245 and 75 Ma. These scenarios match the 2.50 

percent Rm with the corresponding TTl value of 

approximately 2,700. 

At all three localities, the rocks probably reached 

maximum thermal maturity during maximum burial 

between 68 and 65 Ma. As a result of the Laramide 

orogeny (approximately 65 to 37 Ma), the Eagle basin 

was uplifted and subsequent erosion led to "cooling"; 

hence, temperatures as great as those at maximum burial 

were never again reached. Tertiary intrusives emplaced 

south of the study area between 30 and 10 Ma probably 

had little or no effect on increasing the thermal maturity 

of the rocks. 
The Campbell Creek/No. 2 

Gas/Peerless/Powellton Coal Bed 

Correlation from the Middle Part of the 

Kanawha Formation of the 

Central Appalachian Basin 

J.T. O'Connor 

Coal geologists mapping coal resources in the 

Kanawha Formation of West Virginia have since the turn 

of the century defined two benches of the Campbell 

Creek coal bed: the Peerless bench and the No. 2 Gas 

bench. These two benches have more recently been 

mapped as separate beds and have even been 

distinguished from a third bed that has itself been named 

the Campbell Creek coal bed. All these names have been 

applied to and interchanged with the Powellton coal bed. 

Discriminant analysis of major- and trace-element 

constituents of the Kanawha Formation coal beds has 

shown that groups of chemically related coal beds occur 

in zones separated by recognizable marine incursions. 

The chemical composition of coal beds from different 

zones generally varies more than that of coal beds from 

the same zones, although discrimination of some beds 

from within such zones is feasible. In this study we have 

classified the existing analyses of coal beds identified as 

being part of the Campbell Creek/No. 2 Gas/Peerless/ 

Powellton coal group in an attempt to assist in the 

classification and gain information on the depositional 

environment of middle Kanawha time. 

The four beds of this study occur in a single zone of 

the middle Kanawha, although some evidence exists for 

marine influence between the Powellton and the Campbell Creek coal beds. Detailed analysis of 51 samples of 

these coal beds in the USCHEM file of the National Coal 

Resource Data System (NCRDS) indicates that analyses 

attributed to the Campbell Creek, No. 2 Gas, and Powellton coal bed samples are more similar to each other than 

to analyses attributed to the Peerless coal bed samples 

(table 1). The elements that contribute most significantly 

to the variance of the data set were determined by 

principal component analysis to be five sets probably 

related to plant sources or argillaceous affiliations, a set 

probably related to sulfogenic sources, a set probably 

related to epigenetic marine influence, and two sets 

possibly related to source area chemistry or argillaceous 

affiliations. These elements account for 69 percent of the 

total variance of the data set encompassing the Kanawha, 

New River, and Pocahontas coal beds. 

Considering the discontinuous nature of the 

deposition of the coal beds in this part of the Kanawha 

Formation and the use of unchecked existing names for 

the coal beds in question, this analysis may indicate a 

change in source area chemistry or depositional 

conditions between the lower and upper part of this coal 

zone or could be attributed to systematically unreliable 

geologic information in the USCHEM files. Combination of the analyses of the Peerless, Powellton, and 

other coal beds similarly situated in the Kanawha 

Formation and treating these coal beds as geologically 

and geochemically contiguous may assist in defining 

depositional environmental characteristics for the lower 

delta plain environment of the Pennsylvanian Period. 

39 

Table 1. Discrimination of the Peerless coal bed from 

the Powellton group of coal beds 

Unit Geologic 

environment 

Peerless coal Passive lower 

bed. delta plain; 

occurs 

closely below 

Campbell 

Creek 

marine zone; 

often named 

as a bench 

of the 

Campbell 

Creek coal 

bed; may be 

thin (<1ft 

thick), split, 

and discontinuous. 

Powellton 

group 

(Campbell 

Creek, No. 

2 Gas, 

Powellton 

coal beds). 

Passive lower 

delta plain; 

occurs 

closely above 

Cannelton 

marine zone 

but below 

Peerless coal 

bed; often 

thin(<lft 

thick), split, 

and discontinuous. 

Disc rim. 

character 

Hg v. high 

Lu high 

F high 

Ag high 

Br high 

S03 high 

Al20 3 high 

Hflow 

Selenium in Coal from the 

Powder River Basin, 

Wyoming and Montana 

Stat. 

signif. 

Moderate 

discrimination 

between 

groups at 

100 pet for 

51 samples; 

Wilks' 

lambda = 

.128 after 

15 steps. 

C.L. Oman, R.B. Finkelman, S.L. Coleman, and 

L.J. Bragg 

Selenium (Se) in coal has attracted considerable 

attention as a potential environmental hazard, especially 

in many Western States, where environmental regulatory 

agencies require monitoring of selenium in overburden 

and spoil materials as well as in ground and surface 
water. Data stored in the National Coal Resources Data 

System (NCRDS) were used in this study to determine 

the geographic and stratigraphic distribution of selenium 

in coal samples from the Powder River basin, Wyoming 

and Montana. The samples used were primarily from the 

subbituminous coal beds in the Paleocene Tongue River 

Member of the Fort Union Formation. All concentrations are reported on a dry, whole-coal basis; the 

geometric mean for Se in 732 samples is 0.94 ppm. The 

maximum concentration detected was 12.6 ppm. 

On a whole-bed basis, a distinct trend appears in 

the selenium distribution within the basin. Selenium 

concentrations decrease from 1.7 ppm south of lat 44° N. 

to 1.2 ppm in the central part of the basin between lat 44° 

and 45° N. to 0.7 ppm north of lat 45° N. The ash content 

of the coal also decreases from 12.5 weight percent in the 

south to 10.7 weight percent in the central part of the 

basin to 9.0 weight percent in the north. 

Average selenium concentrations appear to be 

higher in younger coal beds; the younger Canyon coal 

bed has the highest average Se concentration (2.4 ppm) 

whereas the older Pawnee coal bed has the lowest 

concentration (0.7 ppm). Vertically within the Canyon 

coal bed, selenium, ash, organic sulfur, and pyritic sulfur 

correlate positively. The peak concentrations of these 

components show no vertical preference within the 

Canyon coal bed. 

A positive statistical correlation exists between Se 

and ash (r = 0.62) for the 732 samples. The correlation 

of selenium with ash in the Powder River basin coal is 

stronger than the selenium-ash correlation in every other 

coal basin in the United States except the Denver basin. 

Selenium in the Powder River basin coals studied also 

correlates strongly with elements generally associated 

with detrital particles (such as Si, AI, K, Ti, La, Rb, Sc, 

Ta). In contrast, a poor correlation (r = 0.3) exists 

between Se and pyritic and sulfate sulfur. The correlation 

of Se with organic sulfur is weak (r = 0.4) in the southern 

and central parts of the basin but very strong (r = 0.81) 

in the northern part of the basin. 

A chemical and mineralogical study of the mode of 

occurrence of selenium in selected coal and overburden 

samples in the Gillette, Wyoming, area indicates that 

selenium occurs in several chemical forms. Organically 

associated selenium may be the most common form of 

this element. Other modes of occurrence for selenium in 

these samples are (1) selenium-bearing pyrite, (2) lead 

selenide, (3) ion-exchangeable cation (perhaps 

associated with clays), ( 4) selenium-bearing galena, and 

(5) water-soluble forms (perhaps as selenate salts) 

commonly in oxidized sediments. 

The seemingly paradoxical correlation of selenium 

with both ash and organic sulfur can be explained if the 

water transporting the detrital particles also carried 

dissolved selenium and sulfur into the Powder River 

40 

basin. This suggestion is consistent with R.M. Flores' 

1986 model postulating that these coal beds accumulated 

in swamps marginal to northerly-flowing streams. The 

decreasing ash content of the coal beds from south to 

north is also consistent with the concept that rocks south 

of the basin are the principal source of detritus. The 

source of the selenium may be seleniferous Cretaceous 

sedimentary rocks, such as the Niobrara Formation, 

which commonly crop out south of the basin. 

Diagenetic Transformations and 

Phosphate Mineral Precipitation in 

Marine Lakes of the Palau Islands 

W.H. Orem, W.C. Burnett', W.B. Lyons2

, W. 

Landing', and P. Chin' 

Many island arcs consist partially or predominantly 

of uplifted carbonate reefs. These elevated limestone 

islands commonly contain marine lakes on stranded 

lagoons connected to the sea only through fissures and 

solution channels in the permeable rock. The stable 

environment and high productivity of these lakes make 

them ideal sites for studies of sedimentation and diagenesis. In addition, such marine lakes could be an 

environment in which some insular phosphate deposits 

were formed. Finally, many deep marine lakes on tropical 

islands are highly stratified and exhibit anoxic hypo limnia, making them ideal model environments for studies 

of geochemical processes across redox boundaries. 

Our initial study of diagenetic processes and 

phosphate deposition in marine lakes focused on Jellyfish 

Lake, on the island of Eil Malk in the Palau Islands. This 

lake was chosen for study because (1) some background 

chemical and physical data on the lake appear in the 

literature; (2) the lake contains an anoxic hypolimnion 

and a bacterial mat at the redox interface; (3) some small 

phosphate deposits, possibly of subaqueous origin, are 

located on Eil Malk and elsewhere in Palau, allowing 

direct comparisons between phosphate minerals in lake 

sediments and nearby phosphorite deposits. 

Sampling of the lake water and coring of the 

bottom sediments were carried out from a moored raft. 

On-site chemical analysis of the lake water and sediment 

pore water covered a number of parameters, including 

phosphate, ammonium, silicate, alkalinity, pH, chloride, 

fluoride, sulfate, and sulfide. Other analyses of the water 

samples and sediment studies (such as mineralogy, 

1

Florida State University, Tallahassee, FL. 2

University of New Hampshire, Durham, NH. 
Ammonium b. 

Phosphate • 

Fluoride • ,....,. 

E 

'-' 

:c 

~ 

a.. 

w 

0 

,....,. 

E 

0 60 

'-' 

:c 

~ 

a. 

w 120 

0 

AMMONIUM (J.tM) 

0 100 200 300 

PHOSPHATE ~M) 

00 20 40 

10 

20 

30 

+<... Anoxic •=····· 

•• .~ .. ~ 

...... ... ..... .... 

• ........ /!:,. . , .' I 

.• I , .:::+A .. ..... A 

PHOSPHATE (J.lM) 

• 

f 

t 

• t 

FLUORIDE (~M) 

68 

Figure 1. Overlying water and pore-water concentrations of ammonium, phosphate, and fluoride from 

Jellyfish Lake, Palau. A, overlying water values; 8, pore-water values for these parameters. p,M, micromolar. 

41 
radiochemistry, organic geochemistry, and major and 

trace elements) were reserved for laboratories in the 

United States. 

Large changes in the concentrations of most 

chemical species were observed across the redox 

boundary (14-15 m), as shown in figure lA. Phosphate 

and ammonium concentrations in the bottom water 

reached concentrations many times that in the surface 

water (40 and 400 times, respectively). Excess phosphate 

relative to total nitrogen was detected at the redox 

interface and just above the sediment/water interface. 

This excess phosphate probably resulted from the 

preferential degradation of organic phosphorus 

compounds by bacteria at these interfaces. (Similar 

excess phosphate concentrations have also been 

documented in pore waters of areas such as the Peru 

upwelling region, where phosphorite is known to be 

forming today.) Further evidence that phosphate 

minerals may be forming in these lakes comes from the 

pore water data (fig. lB), which show a gradual decrease 

in fluoride concentration and a subsurface maximum in 

phosphate concentration. This loss of fluoride may be 

indicative of the formation of calcium fluorapatite 

minerals in the sediments. Mineralogical work will 

attempt to identify this phase in the sediments. 

Organic geochemical studies have shown that the 

sediment is a mixture of algal and vascular plant residues 

and CaC03 debris. The proportion of organic residue 

originating from algae appears to increase with distance 

from shore. The major change in the organic matter with 

increasing depth in the sediments is loss of 

carbohydrates, as shown by 13C nuclear magnetic 

resonance spectroscopy. However, substantial degradation of the organic matter even in the surface 

sediments, as indicated by a low carbohydrate content 

relative to fresh plant material, may have been caused by 

its long residence time in the water column prior to 

deposition. Studies are underway to identify specific 

biomarker compounds in the sediments and nearby 

phosphorite deposits in order to establish a genetic 

relationship. 

The Association of Uranium with 

Organic Matter in a Uranium-Rich 

Peat Bog in the Carson Range Near 

Lake Tahoe, Nevada 

W.H. Orem, R.A. Zielinski, and J.K. Otton 

Uranium accumulates in surficial, organic-rich 

sediments of the Western United States and Western 

Canada where donor rock such as granite is being 

leached of uranium by shallow ground water. The 

42 

organic-rich sediments are generally late Pleistocene to 

Holocene in age and are deposited along low gradients or 

ponded floors of stream valleys. The uranium is largely 

associated with the organic matter in these deposits, but 

the mechanisms of uranium entrapment are not well 

understood. We have investigated the nature of this 

association in the sediment and pore water of a small 

wetland, informally referred to as Upper Zephyr fen, 

located approximately 3 km east of Lake Tahoe on the 

west flank of the Carson Range. During August 1985, 

two cores each were obtained from two different sites in 

Upper Zephyr fen. One core from each site was reserved 

for pore-water studies, and a second core from each 

location was used for sediment studies. 

The sediment in the fen extended to a depth of 

about 4.5 m; organic matter content ranged from 10 to 98 

percent. The upper 3 m of sediment consisted mostly of 

a true peat, whose uranium content averaged 1,700 ppm 

(dry weight basis) but reached values as high as 5,100 

ppm. Spectroscopic analysis of the peat using 13C nuclear 

magnetic resonance spectroscopy (NMR) showed that 

the major change in the chemical structure of the organic 

matter is the loss of carbohydrates with increasing depth. 

A correlation between this loss of carbohydrates and the 

uranium content of the peat was not observed, indicating 

that the uranium may be associated with a more 

refractory component of the peat, possibly lignin or 

aliphatic residues. 

In the pore water, uranium concentrations 

averaged about 42 ppb, but ranged to 95 ppb. These 

values were considerably higher than the overlying water 

value of 20 ppb uranium. Ultrafiltration revealed that 90 

percent or more of the dissolved uranium is associated 

with high-molecular-weight compounds, indicating that it 

is probably associated with dissolved organic matter. 

Indeed, a strong correlation (? = 0.931) was observed 

between dissolved organic carbon (DOC) and dissolved 

uranium in these pore waters (fig. 1). Studies underway 

will help to determine with what fraction(s) of the 

dissolved organic matter the uranium is associated. 

Reconnaissance of Colorado 

Front Range Bogs for 

Uranium and Other Elements 

Douglass E. Owen, R. Randall Schumann, and 

James K. Otton 

Alpine bogs in the Colorado Front Range 

commonly form along spring lines in valley floors and in 

areas where drainage is restricted by moraines, slides, 

and beaver dams. The bogs generally lie between 7,000 

and 10,000 feet elevation and are geologically young (late 
100 

y = 2. 1 Ox-31. 1 "6 I 

I 80 

r

2 =0.931 • 2 1.78x-26.37 r = 0.737 

~ 60 -8. 

c. 

~ 

:::> 40 

• Core 3 

20 :~ .- eliminate outliers .. Core 4 

'-----· 

0 

0 20 40 60 80 100 

DOC (mg/1 C) 

Figure 1. Pore water uranium versus DOC concentrations in two cores from Upper Zephyr fen. Two correlations are 

shown, one including all data with an r 2 value of 0.737 and the second eliminating two outlier points and having an r 2 

value of 0.931. DOC in milligrams per liter carbon. 

Pleistocene or early Holocene to late Holocene). The 

alpine bogs are also locally referred to as fens and 

commonly appear to be meadows from a distance. The 

bogs contain peat and organic-rich muck from a few 

decimeters to several meters thick. Peat has a great 

affinity for highly charged cations such as uranyl 

(U02 

2 +) that can be complexed and carried in local 

ground water. The geochemical enrichment factor 

between peat and uranium -bearing ground water can 

approach or exceed 10,000 to 1. As the bog sediments are 

geologically young, the uranium is in gross disequilibrium with its daughters, and the resultant low gamma 

radioactivity makes these occurrences undetectable by 

ground and aerial gamma ray surveys. 

Reconnaissance auger sampling of bogs was 

conducted in the Colorado Front Range from the South 

Park area to the Colorado-Wyoming State line. Samples 

were dried and analyzed for elemental uranium and 

43 

thorium using a delayed neutron activation technique. In 

addition, some of the samples were analyzed for 44 

elements using ICP-OES (inductively coupled plasmaoptical emission spectrometry). Most of the bogs have 

uranium concentrations in the 10-100 ppm range; 

however, samples from several of the bogs have uranium 

concentrations as high as 1,000-3,000 ppm on a dry 

weight basis. Some of the bog samples show 

concentrations of between 100 and 1,000 ppm for 

barium, manganese, strontium, and zinc. Bismuth, 

chromium, cobalt, copper, gallium, lead, nickel, tin, and 

vanadium were found in concentrations between 10 ppm 

and 100 ppm on a dry weight basis in some of the 

samples. These elements are not necessarily associated 

with high uranium concentrations. 

Some of the bogs, in addition to being mined for 

peat, may contain enough uranium to be of commercial 

interest. Furthermore, uraniferous bogs are of 
environmental concern because of the previously 

unrecognized risk to local water quality. Uranium (and 

other metals) could be remobilized from the peat during 

interaction with acid mine drainage or during oxidation 

following a lowering of the water table or draining of the 

bogs. 

Applying Aromatic Steroids to 

Determination of Thermal Maturity of 

Biodegraded Heavy Oils, 

Tar Sands, and Bitumens 

James G. Palacas, Donald E. Anders, and 

J. David King 

Petroleum explorationists have often experienced 

difficulty in determining the maturity and in turn the 

source of biologically altered heavy oils, tar sands, solid 

bitumens, and oil-stained rocks. Such biodegraded 

hydrocarbon deposits commonly are partially or totally 

depleted in standard geochemical fingerprints-such as 

n-paraffin and isoprenoid distributions, in particular 

pristane and phytane-thus rendering oil-to-oil and oilto-source rock correlations difficult. 

Using computerized gas chromatography-mass 

spectrometry, identification of specific biologic marker 

compounds permits reasonable assessment of the 

maturity and source of migrated oils. Our study focuses 

on the application of the monoaromatic-triaromatic 

steroid compounds as viable maturity indicators. The 

chief advantages of using aromatic steroids rather than 

other steranes or terpanes for maturity assessment are 

that (1) they are relatively more resistant to bacterial 

degradation and (2) collectively, aromatization reactions 

(transformation of monoaromatics to triaromatics) and 

triaromatic cracking reactions (conversion of high 

molecular weight components to lower molecular weight 

components) occur over a wider range of thermal maturities. 

Using a combination of monoaromatic/triaromatic 

and triaromatic steroid ratios, we have determined semiquantitative levels of thermal maturity for a variety of 

biodegraded oils occurring in different geologic settings. 

In the overthrust belt of western Greece, heavy oils from 

seeps were shown to have been derived predominantly 

from two sources: marginally mature and mature facies 

that may range in age from earliest Cretaceous to 

possibly Triassic. In the Tertiary lacustrine rocks of the 

.Uinta Basin, Utah, the oils in tar sands at Sunnyside 

appear to have been derived from shallow, immature, or 

at best marginally mature source facies. In contrast, the 

oils in tar sands of the Permian White Rim Sandstone 

Member of the Cutler Formation, Tar Sand Triangle 

44 

area, southeastern Utah, originated in relatively more 

mature organic facies than those at Sunnyside. 

Interestingly, the oils in the tar sands of the Triassic 

Moenkopi Formation, Vermillion Creek area, 

northwestern Colorado, have maturity signatures 

comparable to those in the Tar Sand Triangle area, 

indicating that the Moenkopi oils were also derived from 

source rocks of similar maturity. 

Ideally, establishment of downhole profiles of aromatized steroid indices together with other maturity 

profiles (vitrinite reflectance, thermal alteration index 

(TAl), bydrocarbons/org C) in nearby wells could (1) 

assist in pinpointing more precisely the depth interval of 

the probable source facies, (2) permit correlation of the 

steroid indices to other viable maturity indicators, and 

(3) help evaluate the effect of source input, if any, on 

these aromatic steroid indices. 

Trace-Element Analysis of 

Vitrinite ConcentratesNew Approach for 

Determining Organic and 

Inorganic Affinity 

Curtis A. Palmer, Paul C. Lyons, and 

Janet D. Fletcher 

The chemical form (organic or inorganic) in which 

trace elements exist in coal is critical to the 

understanding of the chemical and physical processes of 

coal formation, such as the source of mineral species (for 

example, detrital, syngenetic), the processes of traceelement fixation, and mobilization of trace elements 

during coalification. A new method is proposed for 

classifying the trace-element affinities in coals using 

ratios of trace-element concentrations (TEC) in vitrinite 

concentrates (vit) and TEC in companion whole coals 

(ewe). 

Twelve vitrinite-rich, medium- and high-rank 

mined whole-coal samples and corresponding vitrinite 

samples were analyzed for 37 elements by instrumental 

neutron activation analysis and d.c. arc spectrography. 

Generally, the ash contents of the vitrinite concentrates 

were less than 1 percent; in comparison, the ewe samples 

contained from 2.5 to nearly 40 percent. The associations 

of trace elements can be classified by the following 

elemental relationships: 

1. TECvitffECcwc > 1 indicates vit (organic) 

affinity 

2. TECvitffECcwc = 1 indicates either vit 

(organic) or ewe (inorganic) 

3. TECvitffECcwc < 1 indicates ewe (nonvitrinite) affinity 
Chemically, the samples fall into two major 

divisions, low vitrinite affinity (2-7 elements) and high 

vitrinite affinity (10-13 elements) as illustrated in figure 

1. These differences are probably due to variations 

among coal provinces, precursor plant components, 

paleoclimatic factors, and geochemical processes. 

Curiously, the only coals with high vitrinite affinity are 

the British coals and the Australian coal. Sodium (fig. 1) 

and magnesium (fig. 1) have vitrinite affinity in only one 

coal. (See p. 46 for fig. 1.) 

A summary of organic and inorganic affinities, in 

order of decreasing organic affinity, for all samples in this 

study follows: 

Low vitrinite affinity High vitrinite affinity 

Nine eastern U.S. Three foreign coals 

coals 

Appalachian ( 6), Pennine (2 British) 

Illinois (2) and and Sydney (1 

Narragansett (1) Australian) Basins 

Basins 

Always organic Br Br, As, Cr, Sb 

Generally organic v,w V, W, Ni, Cs, Hf, U 

(> 67 pet of 

samples) 

Organic or inorganic B, Sb, Se, U, Zn B, Ba, Se, Sr, Zn 

Generally inorganic Al, As, Ba, Ca, Ce, Al, Ca, Ce, Co, Cu, 

( > 67 pet of samples Co, Cr, Cu, Eu, Ga, Eu, Ga, Hf, Hg, La, 

Hf, Hg, La, Mg, Mn, Mg, Mn, Na, Rb, Sc, 

Na, Ni, Rb, Sc, Si, Si, Sm, Ta, Tb, Ti, 

Sm, Ta, Tb, Ti, Th, Th,Yb 

Yb 

Thermal Maturation of the 

Eastern Anadarko Basin, Oklahoma 

Mark J. Pawlewicz 

Thirteen wells were sampled in a profile across the 

eastern Anadarko basin, Oklahoma, from the northern 

shelf area near the Kansas State line, 125 miles (200 km) 

south to the deep portion of the basin in Caddo County, 

Oklahoma. Vitrinite reflectance measurements on these 

samples show that the level of thermal maturity of the 

sedimentary organic matter was set after maximum 

burial, by synorogenic heating. 

Burial history reconstruction curves show the 

tectonic evolution of this area. Vitrinite reflectance 

measurements indicate temperatures higher than those 

generally accepted for the onset of hydrocarbon 

generation, and also higher than those found by other 

workers in the basin. Regression analysis yields a 

reflectance gradient of 0.109 percent Rm!l,OOO ft (300 

m). The 0.6 and 1.3 percent Rm isoreflectance lines 

define the interval of the oil window along the well 

45 

profile. These lines can be used to estimate the level of 

thermal maturity of source rocks, and their volume. This 

information, in turn, can be used to estimate the volume 

of hydrocarbons generated by those rocks whose thermal 

maturity is within or above the oil window. Also, the 

generation potential of the thermally immature source 

rocks can be estimated by considering their volume 

above the 0.6 percent isoreflectance line. 

Comparative Quality of the 

Upper and Lower Freeport 

Coal Beds in the Appalachian Basin 

Brenda S. Pierce and Ronald W. Stanton 

The Upper and Lower Freeport coal beds in westcentral Pennsylvania consist of facies that are continuous 

over an area of 120 square miles and about 25 square 

miles, respectively. Each facies is distinct in its megascopic, petrographic, and washability characteristics. In the 

Upper Freeport coal bed, three coal facies (table 1, C, D, 

E) and one parting (LP) are continuous, and as many as 

five additional coal facies and one parting are 

discontinuous. In the Lower Freeport coal bed, four coal 

facies (C2, C3, C4, CS) and one parting (P2) are 

continuous, and one coal facies and one parting are 

discontinuous. (Seep. 47 for table 1.) 

These coal beds are interpreted to represent two 

types of peat formation in fluvial-lacustrine-swamp 

environments. In both swamps, peat began forming on a 

substrate of subaerially exposed limestone or flint clay. 

The lowermost facies of each bed (E and CS) have ash 

yields (table 1) resulting from finely laminated mineralrich layers. These ash yields are attributed to intermittent 

detrital influx from adjacent stream channels that 

interrupted peat accumulation. In both settings, the 

detrital influx was areally extensive, covering the entire 

peat body and forming the clay-rich precursor to the 

lower partings. 

After deposition of the partings, peat accumulation 

resumed and produced a series of facies in each bed. The 

Lower Freeport peat continued to evolve in much the 

same environment after deposition of the lower parting, 

forming a repetitive series of laterally extensive facies. 

The Upper Freeport, on the other hand, seems to have 

developed in different environments after deposition of 

the lower parting. Facies C and D have much higher 

vitrinite contents and lower inertinite contents than are 

found in the Lower Freeport facies. Facies C also has a 

much lower ash yield than the Lower Freeport facies. 

After the formation of facies C, fresh-water lakes formed 

over most of the swamp, terminating peat development in 

these areas. In the rest of the swamp, peat formation 
SiAl KFeCaMgNaT i VMnAs B BaBrCoCrCsCuGaHfHgNiRbSbSeSrTaTh U WZnSclaEuYb 

0 

~ 

0 

0 

w 

.... 

..... 

... 

·:; 

0 

w 

.... 

0 

~ 

0 

0 

5 

2 

1 

0.5 

0.2 

0.1 

0.05 

0.02 

5 

2 

1 

w 0.5 .... 

..... 

... 

0 

·:; 0.2 0 

0 

~ 0.1 

0.05 

0.02 

(!) 

0 

0 

t 

0 0 

Ra~Mond Coal, LP-7 

Kanawha Count~, WV 

Appalachian Basin 

U.S.A. 

0 

Liddell coal, LP-19 

New South Wales S~dne~ Basin 

Australia 

Figure 1. Comparison of TECv1t!TECcwc ratios for a U.S. coal and an Australian coal. Error bars indicated by vertical line are 

based on instrumental activation analysis counting statistics. A single dot in center of symbol indicates element determined by 

d.c. arc spectrography. Elements not plotted are below detection limit in vit and (or) ewe. 

continued locally as peat islands forming facies B, A', and 

A. These facies have much lower vitrinite contents and 

much higher inertinite contents than the rest of the coal 

bed. 

That the physical and chemical nature of the peat 

in both swamps at the C3-C4 and C-D stages of 

formation inhibited inundation of the swamps is 

indicated by the restriction of the upper parting (Pl) to 

the margins of the peat body. Furthermore, samples of 

C4 from the margins of the swamp have ash contents 

greater than 20 percent; the more interior locations have 

46 

much lower ash yields ( s 12 percent). The very low ash 

yields of facies C3 and C are also attributed to this 

restriction of detrital influence. 

Although both coal beds formed in 

fluvial-lacustrine-swamp settings, the coal bed facies are 

different. The Lower Freeport developed a repetitive 

series of facies, whereas the Upper Freeport formed as a 

succession of different facies. The differences in quality 

and washability characteristics of these coal bed facies 

are related to variations in peat formation and associated 

mineral and maceral compositions. 
Table 1. Quality data of the Lower Freeport and Upper Freeport coal beds 

[Fac, facies; N, number of samples; Thk, thickness in inches; Ash, percentage ash; Sui, percentage sulfur; R 1.4, weight percent recovery at float 

1.4 specific gravity; Vit, total vitrinite, mineral matter free basis; lnt, total inertinite, mineral matter free basis; Ex, total exinite, mineral matter free 

basis; blank, no analysis run] 

Lower Freeport 

Fac N Thk Ash Sui R 1.4 Vit 

C1 3 8.7 9.17 3.3 86.86 61 

C2 6 16.0 11.99 2.3 78.54 60 

C3 6 15.2 9.11 1.2 87.85 68 

P1 12.0 

C4 5 11.9 17.73 1.1 59.76 75 

P2 0.9 

C5 5 13.9 12.17 0.7 78.11 64 

Preliminary Facies Analysis of the 

Sequence of Rocks Below the 

Upper Wyodak Coal Bed, 

Paleocene Fort Union Formation, 

Southeastern Powder River 

Basin, Wyoming 

Int 

22 

20 

16 

9 

18 

Frances Wahl Pierce and Edward A. Johnson 

Ex 

17 

19 

15 

16 

17 

We conducted a preliminary facies analysis of as 

much as 646 ft of the rock sequence below the upper 

Wyodak coal bed, Paleocene Fort Union Formation, at 

three locations along the southeastern margin of the 

Powder River Basin, Wyoming. Channel, overbank 

sandstone, floodplain, and swamp facies are recognized. 

We believe these facies were deposited on an alluvial 

plain. 

In the main study area, the channel facies is 

characterized by channel-form, fine to very fine grained 

sandstone bodies 10-50 ft thick that fine upward and 

have erosional bases. Lower parts of these bodies are 

trough cross stratified or convolute bedded. Upper parts 

generally consist of thin-bedded sandstone with rare, 

poorly developed ripple laminations and mudrock 

partings. Paleocurrent measurements indicate sediment 

transport to the north and west. 

Interchannel areas are represented by the three 

remaining facies noted. The overbank sandstone facies is 

represented by fine to very fine grained tabular beds 

about 1-7ft thick. Basal contacts are generally sharp and 

upper contacts are sharp to gradational. Lower parts of 

these beds are usually featureless; upper parts are 

parallel laminated or display poorly developed ripple 

laminations. Burrows, fluid escape structures, and 

weakly developed paleosols are also present. We 

interpret the overbank sandstone facies to represent 

47 

Upper Freeport 

Fac N Thk Ash Sui R 1.4 Vit Int Ex 

A 4 14.5 36.20 2.8 51 47 2 

A' 3 12.0 38.90 1.4 61 38 2 

B 7 20.0 12.24 2.3 72 26 2 

UP 7.0 

c 21 28.0 6.99 2.4 89.19 86 10 4 

D 14 21.0 12.40 1.7 78.28 89 9 2 

LP 3.5 

E 13 14.0 24.61 2.2 67.42 89 10 1 

crevasse splay or sheet flood deposits. The floodplain 

facies consists primarily of rooted gray mudrock 1-30ft 

thick with zones of ironstone concretions. The mudrock 

is commonly laminated and contains abundant fossil 

plant debris. This facies accumulated on a floodplain that 

was probably permanently saturated by a high water 

table. The swamp facies consists of brown to black 

carbonaceous shale 1-17 ft thick and coal beds 1-7 ft 

thick. 

In outcrop, these facies occur in laterally 

continuous zones that we call sandstone-dominated and 

mudrock-dominated complexes. These complexes are 

arranged vertically in an alternating sequence, possibly 

reflecting the migration of meandering fluvial channels 

across the alluvial plain. 

Eleven miles to the north and 13 mi to the south, 

additional outcrop studies identified similar facies in the 

interval below the upper Wyodak coal. To the north, the 

facies occur in almost the same proportion as in the main 

study area, but to the south, facies of the interchannel 

areas are much more common than the channel facies. In 

neither outlying area can we recognize sandstonedominated complexes as we can in the main study area. 

We believe that the changes in facies proportion and 

arrangement can be explained by different depositional 

processes operating in each of the three areas. 

By analyzing facies and interpreting the 

environment of deposition, we are beginning to reconstruct the paleogeography of part of the southeastern 

Powder River Basin just prior to the accumulation of 

peat that resulted in the economically important Wyodak 

coal deposit. By understanding the conditions preceding 

the accumulation of this peat, we are gathering 

information that will enable us to design a model 

depicting the origin of the deposit. Such a model could be 

used by the mining industry to help develop exploration 

and mining plans. 
Diagenetic Evolution of Deep 

Hydrocarbon-Bearing Rocks in the 

Ordovician Simpson Group, 

Anadarko Basin, OklahomaEvidence from Mineralogic, 

Stable Isotope, and 

Fluid Inclusion Studies 

Janet K. Pitman and Robert C. Burruss 

The Simpson Group in the southeastern Anadarko 

basin consists of transgressive-regressive cycles of interbedded sandstone, carbonate, and mudstone deposited in 

a shallow marine environment in the southern Oklahoma 

aulacogen. Submature to supermature quartzarenites 

and immature subarkoses, at present burial depths of 

11,000-17,000 feet, display two stages of petroleum 

migration and a complex diagenetic history involving (1) 

precipitation and dissolution of iron-free and 

iron-bearing carbonate, (2) formation of abundant authigenic quartz, and (3) development of a clay mineral 

assemblage. Combined petrographic, stable isotope, and 

fluid inclusion data in conjunction with the modelled 

reconstructed burial and thermal history of the basin 

permit interpretations of the paragenetic sequence. 

The earliest diagenetic stage is represented by rare 

occurrences of dead oil that locally fills primary pores, 

occurs between quartz grain and grain overgrowths, 

forms a thin film on incompletely developed quartz 

overgrowths, and is disseminated as opaque inclusions in 

carbonate cement. In a few samples, rare fluorescent oil 

inclusions are trapped at the dust rim between detrital 

grain and grain overgrowth. The first stage of oil 

migration, during early burial, preceded mechanical 

compaction or significant diagenetic alteration that 

preserved the sandstones from further diagenetic 

modification. Iron-free, pore-fill calcite, partially 

replaced by ferroan calcite, also precipitated at shallow 

burial depths before grain compaction or the 

development of quartz overgrowths. Both varieties of 

calcite show the effects of dissolution possibly caused by 

organic acids and C02 released during catagenesis. 

Authigenic illite and chlorite commonly fill secondary 

pores that resulted from the leaching of calcite. Late in 

the diagenetic history during deep burial, zoned, rhombic, iron-bearing dolomite, in many places containing 

inclusions of oil, selectively replaced calcite and iron-rich 

clay. Isotope geochemistry of early- and late-formed 

carbonate shows enriched C> 13C compositions 

characteristic of marine carbonate with little or no input 

from organic carbon. C>18 0 values are depleted, possibly 

reflecting increased temperatures due to greater burial 

depth; the original oxygen isotope composition of waters 

buried with the sediments likely approximated that of 

48 

seawater. Well-developed quartz overgrowths are 

pervasive in quartzarenites, except in areas where 

carbonate cement or hydrocarbons were introduced 

during early burial. Secondary quartz formed during 

moderate burial after framework grain compaction, 

effectively eliminating most porosity in the deepest 

sandstones. A late stage of petroleum migration is 

documented by stylolitic seams and fracture surfaces 

stained by dead oil. In some samples, fluorescent oil 

inclusions are trapped on microfractures that crosscut 

grain boundaries and overgrowths and terminate at stylolites. This second stage of petroleum migration 

occurred in response to deep burial and associated 

regional deformation during the Pennsylvanian age Ouachita orogeny. 

Banks, Reefs, Deltas, and 

Fans-Jurassic-Cretaceous 

Transition in the 

Baltimore Canyon Trough 

C. Wylie Poag, John S. Schlee, B. Ann Swift, 

Mahlon M. Ball, and Linda Sheetz 

The last 10 years have seen a burst of information 

regarding the regional structure and depositional 

patterns of the Baltimore Canyon trough. Early, rather 

generalized interpretations were based chiefly on 

seismic-reflection profiles. To this seismic data base have 

gradually been added geologic data from 34 exploratory 

wells, 18 intermittently cored holes on the continental 

shelf, and 11 continuously cored holes on the continental 

slope and rise. Acquisition of high-resolution seismic 

profiles, reprocessing of older multichannel profiles, and 

refinement of biostratigraphic interpretations now allow 

a fine-scaled reassessment of the geologic evolution of 

this basin. We have begun this second-stage analysis by 

focusing on the Jurassic-Cretaceous transition. 

The Late Jurassic (Tithonian-Kimmeridgian) 

outer continental shelf in the Baltimore Canyon trough 

was a broad carbonate platform, bordered off New Jersey 

by a pinnacled barrier reef. The reef complex is 

structurally highest off southern New Jersey, is lower to 

the north, and is breached by a broad, 2-km-deep channel 

off Ocean City, Maryland. Landward of the reef tract, a 

series of parallel, southeastward-dipping, listric, normal 

faults (the Gemini fault system) break the Jurassic outer 

shelf into a series of elongate, tilted blocks, some 

characterized by rollover anticlines on the downthrown 

sides. This faulting is the result of loading the shelf edge 

with 4 km of post-Jurassic sedimentary rocks. The other 

principal structure is a large igneous intrusion (Schlee 

Dome), whose flanks have been drilled by several 
petroleum tests. Upper Jurassic strata have been eroded 

to <100-m thickness across the crest of Schlee Dome. 

At the shelf edge, a precipitous reef face (25° 

slope) rises as high as 2 km above the adjacent Late 

Jurassic continental rise. A 2-km-thick wedge of reef 

talus and slope-front fill spreads eastward across the 

deep-sea basin (North American basin), thinning on the 

lower rise to <50 m where it was drilled at DSDP Site 

105. 

Following a period of lowered sea level and 

presumed subaerial exposure, during which the southern 

part of the reef tract was breached, Early Cretaceous 

(Berriasian and Valanginian) siliciclastics began to 

accumulate in a thick deltaic wedge behind the shelf-edge 

carbonate barrier. To the north, where the barrier was 

lowest, and at the breach, the Lower Cretaceous debris 

buried the Jurassic shelf-edge carbonates and spilled out 

onto the continental rise as debris flows and turbidity 

currents. That some of these terrigenous components 

spread as far as 500 km southeast of the breach is shown 

at DSDP Site 603, in which 100 m of coaly, sandy 

mudstone and marly limestone was cored. 

Early Cretaceous depositional rates were maximal 

in a large deep-sea fan off northern New Jersey, and in 

the breach off Ocean City, Maryland, where more than 2 

km of Berriasian and Valanginian sediments 

accumulated in 13 m.y. (15 cm/1,000 yr; uncorrected for 

compaction). The reef complex remained a barrier to 

basinward sediment transport off southern New Jersey, 

however; depositional rates seaward of the shelf-edge 

were no greater than 4.5 cm/1,000 yr. 

Relationship of Clay-Mineral 

Diagenesis to Temperature, Age, and 

Hydrocarbon GenerationAn Example from the 

Anadarko Basin, Oklahoma 

Richard M. Pollastro and James W. Schmoker 

The work reported here relates the diagenesis of 

interstratified illite/smectite (1/S) to burial history and oil 

generation and tests the dependence of temperature and 

time on the smectite-to-illite reaction. 

Clay mineralogies of shales and sandstones of 

Morrowan-late Springeran age (Early Pennsylvanian) 

were determined by X-ray powder diffraction (XRD) of 

core samples from a 13-well profile extending northwest 

to southeast across the Anadarko basin, Oklahoma. 1/S 

clay, as defined by XRD patterns, is abundant in both the 

shales and sandstones. Randomly interstratified 1/S 

occurs in many of the shallow samples, but disappears in 

the present-day depth range of 2,750-3,050 m; only 

49 

ordered 1/S is found in samples below 3,050 m. A 

regional vitrinite-reflectance profile compiled for the 

Anadarko basin suggests an average erosional removal of 

about 800 m. Therefore, maximum burial depth of the 

zone where randomly interstratified 1/S disappears is 

about 3,540-3,840 m. 

Published temperature models suggest that, for 

Tertiary and Cretaceous rocks, the transition from 

randomly interstratified 1/S to short-range ordered 1/S 

occurs between 100 and 110 °C. Assuming a constant 

geothermal gradient of 2.37 °C/100 m and burial histories 

as shown in figure 1, maximum temperatures of 100-110 

oc correspond to present -day burial depths between 

2,700 and 3,120 m. These independently calculated 

depths for the 100-110 °C isotherm are in excellent 

agreement with the depths at which randomly interstratified 1/S is observed to disappear in MorrowanSpringeran age rocks. The similarity in temperature for 

the 1/S phase change in rocks of Early Pennsylvanian, 

Cretaceous, and Tertiary age spanning a time of some 

300 million years suggests that time plays a secondary 

role in the diagenesis of these clay minerals. 

The relation between the 1/S transition and oil 

generation in the Anadarko basin is shown in figure 1. 

The nonparallel bands illustrate the different time 

dependence assumed for kerogen maturation and clay 

diagenesis. The burial histories of two areas in the basin 

(A andB, fig. 1) illustrate how clay-mineral diagenesis at 

these locations can be related to stages of hydrocarbon 

generation, the time and tectonic period at which clays 

entered critical temperature windows, and the length of 

time spent at or above critical temperatures. 

Potential Petroleum Source Rocks in the 

Late Proterozoic Chuar Group, 

Grand Canyon, Arizona 

Mitchell W. Reynolds, James G. Palacas, and 

Donald P. Elston 

The Chuar Group, upper part of the Grand 

Canyon Supergroup in northwestern Arizona, is a 1,637-

meter-thick succession of predominantly very fine 

grained siliciclastic rocks that contains thin sequences of 

sandstone and stromatolitic and cryptalgal carbonate 

rocks. More than half the succession consists of organicrich gray to black mudstone and siltstone; fossil 

microorganisms are abundant to common throughout 

successions of dark mudstone and siltstone. 

Strata of the Chuar Group likely accumulated in a 

succession of environments that included a sedimentstarved basin rich in organic material, a coastal or alluvial 

plain, and mixed coastal or paludal swamp and alluvial 
TIME BEFORE PRESENT (MILLIONS OF YEARS) 

350 300 250 200 150 100 50 0 

0 r-------wrT---------~--------~--------~--------~------~~--------~ 0 

J: 

._ 

Q. 

w 

0 

2 

3 

4 

5 

6 

7 

.,,,., -- --p-e'Ai< 

_ _, 

5 

,.... 

0 

0 

0 

...-

X 

._ 

w 

w 

---- LL 

15 """' J: 

._ 

Q. 

w 

0 

20 

Figure 1. Lopatin, burial, and temperature reconstructions for Morrowan rocks, Anadarko basin, Oklahoma, relating ordering 

changes in interstratified illite/smectite (1/S) to burial history and the oil window. Solid lines are burial reconstructions for top of 

Morrowan near wells with (A) randomly interstratified 1/S and (B) only ordered 1/S. Dashed lines are time-depth reconstructions 

for oil generation based on Lopatin modeling. Mottled zone shows 10Q-110 oc temperature band and represents predicted 

upper limit for randomly interstratified 1/S. 

plain environments. Stromatolitic, cryptalgal, oolitic, and 

pisolitic carbonate rocks demonstrate nearshore aqueous 

environments. Depositional sequences of aqueous and 

subaerial settings alike seem to be markedly cyclic. 

In the past, the site of deposition has been 

interpreted as a foundering marine embayment on the 

passive edge of the continent. The character and 

succession of the strata, in conjunction with new possible 

correlations with Late Proterozoic rocks of probable 

marine origin in adjacent parts of the Western United 

States, suggest the alternate hypothesis that Chuar strata 

accumulated in a lacustrine setting in a subsiding region 

within the continent. 

Preliminary analyses indicate that dark mudstone 

from the Chuar Group contains as much as 5 percent 

total organic carbon. Rock-Eval Tmax values, generally 

ranging from 430 to 440 °C, indicate that the rocks, 

particularly in the upper part of the succession, are within 

50 

the principal oil-generating window. Hydrogen index 

(HI) values of as much as 190 mgHC/gC(org)' and genetic 

potentials (S1 +52 ) of as much as 6 kg/ton (6,000 ppm) 

demonstrate that the rocks still have potential for 

generating sufficient amounts of gaseous and liquid 

hydrocarbons for commercial accumulations. 

Chuar Group strata, now exposed only on the north 

side of the Colorado River in the eastern part of the 

Grand Canyon, plunge north beneath the Kaibab Plateau 

of Arizona and southwestern Utah. In the Grand Canyon 

the strata are truncated on the east by a normal fault that 

predates the Cambrian Tapeats Sandstone. We suggest 

that if the Chuar Group is present more widely beneath 

Phanerozoic rocks of the Kaibab Plateau or is preserved 

in pre-Phanerozoic grabens in northern Arizona or 

southern Utah, the strata may have served as source 

rocks for potential petroleum accumulations in lower 

Paleozoic or Proterozoic units yet to be prospected in 

that region. 
Relation of Major Sea-Level Fall and 

Regional Unconformity to Hydrocarbon 

Accumulations, Upper Cretaceous Turner 

Sandy Member of Carlile Shale, 

Black Hills Uplift 

Dudley D. Rice and C. William Keighin 

The Upper Cretaceous (Turonian) Turner Sandy 

Member of Carlile Shale forms a large lobe of interbedded sandstone, siltstone, and shale that extends eastward 

across the Black Hills uplift of northeastern Wyoming, 

western South Dakota, and southeastern Montana. The 

sediments were deposited on the shallow, flat, western 

shelf of a north-south-trending epicontinental seaway. 

The sediments were transported to shelf by a major 

river-dominated delta system located in southwestern 

Wyoming. The Turner lies above the Pool Creek 

Member of the Carlile Shale, on a regional unconformity 

that resulted from marine erosion during global sea-level 

fall in middle Turonian time. 

The Turner Sandy Member consists of two 

sandstone intervals separated by shale. The lower 

interval, which lies directly on the marine erosional 

surface, is as much as 7 m thick and is composed of two 

types of sandstone. One type, medium grained, occurs as 

tabular and cross-stratified sets as much as 1 m thick. 

Paleocurrent measurements indicate a general eastward 

direction of transport. These sandstones filled erosional 

lows in underlying marine shale during sea-level rise. 

Within this medium-grained sandstone are 

conglomeratic lenses containing shark and ray teeth, fish 

vertebrae, shell hash, shale rip-up clasts, wood fragments, 

and pebbles and granules of chert. These lenses are 

transgressive lags. The other type of sandstone in the 

lower interval is very fine to fine grained, displays planar 

lamination, wave-ripple cross-lamination, and some 

hummocky cross-stratification, and has a sharp base with 

occasional sole marks. This type accumulated as more 

widespread sandstone bodies in a shelf environment that 

was occasionally affected by storm activity. 

On the south flank of the Black Hills uplift, the 

upper sandstone interval consists of two thin (1.5 m 

average thickness) very fine grained sandstone units that 

are made up of individual beds intercalated with shale or 

amalgamated. Each bed has a sharp erosional base with 

sole marks and grades upward into shale. Hummocky 

cross-stratification is the dominant type of stratification. 

Wave-ripple cross-stratification is commonly developed 

at the tops of beds or units where beds are amalgamated. 

Trace fossils of Cruziana ichnofacies are restricted to 

rippled surfaces. Lenses and concretions of shells of 

ammonites and bivalves occur at the base of units. 

51 

On the west flank of the Black Hills uplift, the 

upper sandstone interval is as much as 7 m of very fine 

grained sandstone with decreasing intercalations of shale 

upward in the lower part. Planar lamination and 

hummocky cross-stratification are prevalent in the lower 

part. The upper part is thoroughly bioturbated by trace 

fossils of Skolithos ichnofacies. The upper sandstone unit 

at both sites was deposited below fair-weather wave base 

on a storm-wave dominated shelf. On the south flank of 

the uplift, the upward sequence of sedimentary 

structures in individual beds suggests a decrease in 

energy level, indicating waning of storm activity and 

return to fair-weather conditions. On the west flank, 

deposition above fair-weather wave base is suggested in 

the upper part by bioturbation of Skolithos ichnofacies. 

Several oil fields have been discovered in the lower 

sandstone interval of the Turner Sandy Member on the 

southwest flank of the Black Hills uplift. The reservoir is 

composed of beds of medium-grained sandstone that are 

confined to narrow east -west channels that resulted from 

sea-level fall and erosion of underlying marine shale. 

Both sandstone intervals are potential reservoirs for 

biogenic gas on the north, east, and south flanks at uplift 

where mature source rocks are not present. 

Identification and Importance of 

Coal Bed Gas, San Juan Basin, 

Southwestern Colorado and 

Northwestern New Mexico 

Dudley D. Rice, Charles N. Threlkeld, and 

April K. Vuletich 

Coal beds are considered to be a major source of 

nonassociated gas in the Rocky Mountains. In the San 

Juan Basin, northwestern New Mexico and southwestern 

Colorado, significant quantities of natural gas are being 

produced from coal beds of the Upper Cretaceous Fruitland Formation and from adjacent sandstone reservoirs. 

Analysis of gas samples from the various producing 

intervals provides a means of determining their origin 

and of evaluating coal beds as source rocks. 

The rank of coal beds in the Fruitland Formation, 

where major production occurs, increases from 

southwest to northeast: it ranges from high-volatile 

bituminous A to medium-volatile bituminous (Ro values 

0.7-1.4 percent). On the basis of chemical and isotopic 

composition and coal rank, the gases produced are 

interpreted to be thermogenic. Gases from the coal beds 

show little isotopic variation (o13C1 values -43.0 to -40.5 

ppt), are chemically dry (C1/C1 _5 values 0.98-0.99), and 

contain significant amounts of C02 (as much as 6 

percent). These gases are interpreted to result from 
devolatilization, which yields methane, carbon dioxide, 

and water as the primary products. In contrast, gases 

from sandstones in the Fruitland Formation and 

underlying Pictured Cliffs Sandstone have a wider range 

of isotopic values (o13C1 values -43.9 to -39.0 ppt), are 

chemically wetter (C1/C1_5 values 0.86-0.94), and 

contain less C02 ( < 2 percent); these sandstones also 

produce minor amounts of waxy, immature oil. These 

gases are interpreted to have been derived from nonmarine kerogen (Type III) dispersed in marine shales of the 

underlying Lewis Shale and in nonmarine shales of the 

Fruitland Formation. 

These two gas types are distinctly different from 

that of gases associated with oil produced from the 

underlying Upper Cretaceous Dakota Sandstone and 

Tocito Sandstone Lentil of Mancos Shale. This 

associated gas is isotopically lighter and chemically 

wetter at equivalent levels of thermal maturity than those 

derived from coal and dispersed Type III kerogen. This 

gas is interpreted as a product of thermal cracking of 

marine kerogen (Type II). 

Some gas samples from sandstones in the Fruitland 

Formation and Pictured Cliffs Sandstone are almost 

identical in chemical and isotopic composition to those 

from coal beds in the immediate area. These samples 

probably represent gas that migrated from nearby coal 

beds into the sandstone. 

Three types of gas have been identified on the basis 

of chemical and isotopic composition in the San Juan 

Basin: those generated from (1) Type II kerogen, (2) 

dispersed Type III kerogen, and (3) coal beds. Most of 

the coal-derived gas is contained within coal beds, 

indicating that expulsion into adjacent sandstone 

reservoirs has not taken place. 

GLORIA Survey off the 

East Coast of the United States 

J.M. Robb, D.W. O'Leary, W.P. Dillon, P. Popenoe, 

E.A. Winget, J.S. Schlee, D.C. Twichell, 

P.C. Valentine, and K.M. Scanlon 

From February through May 1987, the U.S. 

Geological Survey and the Institute of Oceanographic 

Science (United Kingdom) conducted a long-range 

sidescan-sonar survey of the Exclusive Economic Zone 

(EEZ) off the United States East Coast. The acoustically 

derived images of the sea floor have been assembled into 

a preliminary regional mosaic of the sea bottom 

extending from the Florida Peninsula to Georges Bank 

and the Scotian Shelf. 

The continental slope off New England is deeply 

etched and eroded; much of the continental rise area is 

52 

covered by fairly uniform sheets of debris below 2,500-m 

water depth. Discrete groups of canyons that incise the 

slope converge to form single channels on the upper rise, 

most of which are choked by debris. Only five of the 

canyons that indent the shelf extend as far as the 

boundary of the EEZ; all five maintain their sinuous, 

incised character for great distances. Some canyons are 

linked in a crude reticulate pattern that suggests seafloor tilting or fracturing. Sheets of debris surround 

Picket, Retriever, and Buel Seamounts. All of the New 

England Seamounts are at least partially buried, and 

their surfaces are greatly eroded. 

Off the Middle Atlantic States, the GLORIA 

images show the sharply bounded compartments of the 

continental rise, each dominated by a distinct set of 

processes. Immense areas of bottom failure and landslide 

alternate with areas of smooth deposition. Submarine 

channels, some cut deeper than 300 m below the sea 

floor, cross the ocean floor for more than 160 km. 

Between Baltimore and Toms Canyons, canyons and 

curving channels in a vast dendritic pattern join to form a 

single large channel that extends to the border of the 

EEZ. 

The exceptionally steep continental slope in the 

Cape Hatteras area is characterized by bands of 

outcropping strata that are cut by submarine canyons and 

massive slumps. South of Cape Hatteras, the slope angle 

decreases, and the slope is increasingly covered by 

younger sands and muds of Quaternary age. 

Surface manifestations of diapiric structures have 

been identified off the Carolinas and off New Jersey in 

preliminary mosaics. The Albemarle Slump and another 

slide off Cape Romain are clearly visible on the data. The 

sonographs have mapped a third slide, previously 

unknown and equally large, between them. Long rubble 

trains descend from these slumps and are traceable 

beyond the 200-mile limit of the EEZ. 

Several of the canyons off the Carolinas are now 

known to make abrupt, right-angle turns into a large, 

transverse canyon that parallels the coastline and acts as 

a conduit to the deep sea. A ridge seaward of the 

transverse canyon is covered by massive ripple-like 

features 75 m high and 5 km from crest to crest that 

indicate northeastward sediment movement. 

In the Blake Escarpment area off eastern Florida, 

the mosaics show a 100-km-long current-scoured 

depression extending south from the base of the Blake 

Spur. In the lee of the spur, where the escarpment is 

protected from the strong southward flow, a previously 

unknown set of submarine canyons cuts into the 

escarpment. On the Blake Plateau, Gulf Stream-scoured 

exposures of older strata end abruptly at the crest of the 

"Charleston Bump," where the shelf appears to be 

covered by a sand sheet that is marked only by scattered 
deepwater reef pinnacles. Individual reefs are nearly 1.6 

km wide and as high as 45 m. 

The GLORIA surveys also gathered correlative 

data in the form of echo-sounding, magnetic intensity, 

and high-resolution seismic-reflection profiles along 

track. The data assemblage is combined with known 

seismic and sampling data. These interpretive geologic 

compilations are released to the public in atlas format, 

usually within a year of data collection. The atlas for the 

Pacific coast was published in 1986, and for the Gulf of 

Mexico and the Caribbean in 1987. 

Manganese Binding by Iron Bacteria in 

Wetlands-A Potential Analog for 

Manganese-Rich Coal 

E.l. Robbins, E.W. de Vrind,1 Hans de Vrind,1 and 

W.C. Ghiorse2 

A study of iron bacteria in modern wetlands reveals 

rodlike and doughnut-shaped mineral precipitates that 

may be identifiable in the fossil record. Wetlands that are 

fed by anoxic ground water carrying reduced species of 

Fe(II) and Mn(II) are populated by manganese-binding 

and manganese-oxidizing iron bacteria. Iron bacteria, the 

group of bacteria that precipitate iron oxides, can be 

abundant and highly visible in wetlands that have iron in 

their watersheds; the water is often bright red. The 

dynamics of bacterial precipitation of both iron and 

manganese are quite complex, and not all steps in the 

metabolic pathways are understood or proven. Whether 

the oxidation of Fe(II) or Mn(II) serves as an energy 

source or as a detoxification mechanism, the end product 

is microbially precipitated iron and manganese. 

An important species of iron bacteria that can 

precipitate both metals is Leptothrix discophora. In wetlands, L. discophora often forms oil-like films on water. 

Its filaments have expanded ends which serve as flotation 

disks that attach at the air-water interface. The surface 

film can be collected on a glass slide; microscopic 

examination reveals the presence of characteristic 

rodlike sheaths and doughnut-shaped holdfasts. The 

mineralized sheaths of iron bacteria have been found to 

contain the hydrated iron oxide, ferrihydrite, a 

metastable mineral that can dehydrate to form hematite. 

The coated sheaths also may contain manganese oxides. 

Manganese-binding iron bacteria have been 

studied in three wetland areas in Northeastern United 

1 Department of Biochemistry, University of Lei den, Lei den, The 

Netherlands; research financed in part by Netherlands Organization 

for the Advancement of Pure Research, Z.W.O. 2

Department of Microbiology, Cornell University, Ithaca, N.Y. 

53 

States. Several strains of L. discophora that appear to 

produce manganese-oxidizing proteins associated with 

polysaccharide-protein exopolymers have been isolated 

from Sapsucker Woods Swamp in Ithaca, New York. The 

protein of strain SS-1 has a molecular weight of 110,000 

and is inactivated by treatments such as exposure to 

temperatures higher than 80 °C, detergents, and heavy 

metals, as shown in a 1986 study by L.F. Adams III. It 

catalyzes the reaction: Mn2 + + Y2 0 2 + H2 0 - Mn02 

+ 2H + , obeying Michalis-Menton kinetics suggesting 

that the manganese-oxidizing protein is a bacterial 

enzyme. 

The water of Bear Trap Creek in Syracuse, New 

York, is bright red from the presence of films of L. 

discophora. The L. discophora strain from this water 

loses its sheath-forming ability upon culturing in rich 

media; part of its manganese-oxidizing activity is excreted 

into the medium. It contains at least two proteins with 

manganese-oxidizing activity, as detected with sodium 

dodecyl sulfate-gel electrophoresis. 

The Huntley Meadows wetland near Mount Vernon, Virginia, has extensive areas where ground water 

discharges Fe(II) and Mn(II). The iron bacteria of this 

wetland, Leptothrix discophora, Leptothrix!Sphaeroti/us 

sp., Gallionella, and Siderocapsa, all oxidize manganese. 

Manganese oxide also precipitates on slimy rocks at the 

break in slope between the iron-rich rocks of the 

Cretaceous highlands and the Pleistocene sediments of 

an old Potomac River meander scar where the wetland is 

located; mini-nodules of manganese oxide can be 

collected in certain reaches of the streams. We have not 

attempted to isolate the bacteria on the rocks, but 

submerged glass slides in these reaches become coated 

with the doughnut -shaped precipitates characteristic of 

L. discophora. 

Wetlands that deposit peat and are fed by ground 

water may be useful modern analogs for manganese-rich 

coal. Manganese-bearing coal, such as those in Alabama, 

Colorado, and Iowa, may be the remains of wetlands 

where microbial populations bound manganese and iron 

into minerals that can be recognized as microbial in 

origin. 

Coal Quality and Distribution in 

Upper Cretaceous and Tertiary Rocks, 

East-Central North Slope, Alaska 

Stephen B. Roberts 

Extensive coal deposits underlie a region of greater 

than 4,000 square miles on the east -central North Slope 

of Alaska. The coal-bearing strata, which include rocks of 

both the Upper Cretaceous Prince Creek Formation and 
the Tertiary Sagavanirktok Formation, have been 

interpreted as part of a time-transgressive deltaic 

sequence which prograded generally northeastward. 

Previous workers have estimated the coal resources of 

this region to be 50 to 60 billion tons. Current 

investigations focus on the characterization of the coals 

in terms of stratigraphic occurrence, quality, and areal 

distribution. Coal-bearing outcrops were sampled and 

described, and selected geophysical logs from oil and gas 

wells in the region have been analyzed. 

Surface exposures of the coal beds occur in a belt 

extending more than 50 miles from the White Hills 

eastward to the Kavik River. Sections were measured 

along the Sagavanirktok River near Sagwon, at two 

locations on the Shaviovik River, and at Juniper Creek. 

The coal-bearing outcrops consist primarily of interbedded sandstone, siltstone, shale (mudstone), carbonaceous shale and coal. Sandstones are dominantly fine to 

medium grained and ripple laminated to trough crossbedded; pebble lag occurs at the base of troughs. Shales 

are commonly interbedded with both siltstone and very 

fine grained, ripple-laminated sandstone, and locally the 

shales are bentonitic. Both shales and siltstones contain 

abundant coalified plant fragments. Siderite concretions 

occur throughout the coal-bearing section. 

The coal beds in outcrops range in thickness from 

2 to 12 feet, and many contain layers of coaly carbonaceous shale and bone (high-ash) coal interbedded with 

bright coal. Clay partings are abundant. Analyses of 16 

coal samples from 11 coal beds indicate that the apparent 

rank of the coal ranges from lignite A to subbituminous 

B, and is most commonly subbituminous C. Average 

values for the ash and total sulfur are 7.5 percent and 0.3 

percent respectively. 

Subsurface data on the coal-bearing sequence are 

from oil and gas test wells within the Prudhoe Bay region. 

Interpretation of 10 geophysical logs from wells located 

along a 50-mile line between the Kuparuk and Kadleroshilik Rivers near the Arctic coast indicates that the 

coal-bearing sequence, defined here as the interval 

between the stratigraphically highest and lowest coal 

beds, ranges in thickness from 720 to 1,340 feet. Depth to 

the top of the sequence increases west to east from 2,800 

feet to 5,400 feet. Coal bed thickness ranges from 2 to 25 

feet, with cumulative coal thickness generaJly 

constituting 6-8 percent of the total thickness of the 

coal-bearing interval. 

Results of these investigations will further 

delineate the extent of coal bed occurrence in Upper 

Cretaceous and Tertiary rocks, and better define the coal 

resource potential within this large area of Alaska's 

North Slope. 

54 

Sequential, Time-Slice 

Paleogeography of Northwest Borneo, 

Southeast Asia, as a 

Basis for the Delineation of 

Oil and Gas Plays 

Keith Robinson 

The island of Borneo appears to have formed as a 

result of the southward migration, rotation, collision, and 

accretion of a series of microcontinental blocks. These 

blocks were possibly rifted from the southern margin of 

the Asian continent and then impeded in their southerly 

migration by the Australia-India plate in their presentday location. The blocks were probably transported along 

a complex series of right-lateral transcurrent wrench 

faults, and were associated with, or directly related to 

periods of subduction and sea-floor spreading in both the 

South China Sea and the Makassar Strait. Interaction 

between the plates resulted in the development of major 

sedimentary depocenters and stable shelf areas. 

The present "microcontinental" -margin Tertiary 

basins in Borneo are all fault controlled. These basins 

formed parallel to the coastline, controlled by major 

northwest-trending transcurrent wrench faults. Zones of 

weakness in the pre-Tertiary basement, parallel to the 

coastline, caused the continental margin to collapse in 

response to regional subduction or pull-apart stresses 

and sedimentary loading. The collapse resulted in the 

development of a series of normal faults which drop the 

basement successively seaward, characteristic of a 

continental passive margin. 

Significant hydrocarbon discoveries in Brunei and 

the Malaysian states of Sarawak and Sabah, of northwest 

Borneo, are confined to coastal and offshore Tertiary 

sedimentary basins. The complexity of both the 

depositional history and structural development gives 

rise to numerous exploration play prospects. Controlling 

factors in play development are the environment of 

deposition, the type of sediment deposited in each play 

area, and the structural configuration, or physical 

geometry, of the feature receiving the sediment. 

Structural and sedimentary features controlling 

exploration plays in northwest Borneo include faultbounded horst, graben, and half-graben structures; 

gently folded to highly faulted and asymmetrical anticlines; synsedimentary growth-fault and roll-over 

features; structurally controlled deep-marine turbidites; 

carbonate platforms; pinnacle reef complexes; and delta 

systems. 

A major marine regression in northwest Borneo 

occurred during Paleocene through middle Eocene time, 

in response to intense cordilleran uplift of a young 

mountain range near the present Malaysian-Indonesian 
border. Late Eocene to early Miocene was a time of 

widespread marine transgression. An active subduction 

zone, emergent mountain ranges, marine trenches, 

rapidly-filled marginal basins, and carbonate platforms 

developed during this period. In contrast, middle Miocene through early Pliocene was a time of general 

regression, accompanied by repeated periods of intense 

tectonism. Late Pliocene to the present has been 

characterized by cyclical periods of marine regression 

and transgression. The post lower Miocene period to the 

present has been marked by the development of large 

delta systems, carbonate platforms, pinnacle reefs and 

shallow marine clastic wedges. 

Studies of the tectonic evolution of northwest Borneo and an interpretation of probable associated 

paleoenvironmental conditions that prevailed make it 

possible to reconstruct a scenario of conditions that 

existed at any one time during the Cenozoic era. A 

sequential geologic reconstruction of these conditions, 

through time, leads to the delineation of new potential 

plays and geographic areas for hydrocarbon discovery. 

Current oil- and gas-producing plays in northwest Borneo are predominantly confined to deltaic systems and 

pinnacle reef growths. 

Diagenesis of Sandstones in the 

Permian Upper Part of the 

Minnelusa Formation, West Mellott Field, 

Powder River Basin, Wyoming 

C.J. Schenk, R.M. Pollastro, and J.W. Schmoker 

Dolomite-anhydrite-sandstone cycles of the Permian upper part of the Minnelusa Formation, Wyoming, 

record multiple progradations of marine, siliciclastic 

sabkha, and eolian sediments. Heterogeneity in the 

sandstones, studied in five cores from present-day depths 

between 7,100 and 7,325 feet, is partly the result of 

diagenetic alterations. The earliest alteration was the 

formation of clay coatings on the detrital grains, 

particularly in siliciclastic sabkha and related eolian 

sandstones. Quartz cement formed syntaxial overgrowths, particularly in the sabkha sandstones. 

Carbonate clasts in the sandstones were pervasively 

dolomitized, as were the adjacent carbonate beds, 

possibly by seepage-reflux of brines that formed during 

the evaporitic stage of the next sedimentary cycle. The 

sandstones were then partially cemented with poikilitic 

anhydrite (or gypsum). Clay coatings and cementation by 

anhydrite did not completely prevent a progressive loss of 

intergranular volume by pressure solution with burial. 

The illitization of early clay coatings was also a 

progressive process with burial. The present-day clay 

55 

mineral assemblage in the sandstones consists 

predominantly of illite and ordered illite/smectite. The 

authigenic overgrowth and intergrowth morphology of 

the clay coatings suggest that they were probably more 

smectitic in composition when introduced into the sands, 

and were progressively converted to their present illitic 

composition during burial. 

Late-stage dissolution of anhydrite produced 

irregularly distributed secondary sandstone porosity; 

dissolution was most complete in the upper parts of 

eolian-dune and reworked-eolian sandstones, resulting in 

excellent reservoir properties. Late-stage dissolution of 

potassium feldspars also occurred, as evidenced by the 

lack of compaction of the partially dissolved grains. Small 

rhombs of authigenic dolomite grew along most of the 

secondary pores and partially replaced the remaining 

anhydrite. Laths of authigenic illite formed on the 

dolomite, although this illite phase is rare. Quartz 

cement formed subsequent to the dolomite, in some 

cases engulfing the dolomite rhombs in syntaxial overgrowths. Hydrocarbons then migrated into and occupied 

the secondary porosity of the upper parts of the eoliandune sandstones and reworked-eolian sandstones. Pyrite 

is present as an authigenic phase that automorphically 

replaced anhydrite and quartz, but its position in the 

paragenetic sequence was difficult to determine. 

Sedimentology of the 

Permian Upper Part of the 

Minnelusa Formation near Beulah, 

Wyoming- Analog for Subsurface 

Facies in the Powder River Basin 

C.J. Schenk, J.W. Schmoker, J.E. Fox, and 

M.W. Lee 

Sandstones in the upper part of the Minnelusa 

Formation host an important group of hydrocarbon 

reservoirs. Exploration for additional reservoirs is 

difficult because of a complex intercalation of the 

sandstones with other lithologies. Outcrops near Beulah, 

Wyoming, provide a three-dimensional sedimentologic 

perspective of this complexity, and constitute a unique 

opportunity to refine sedimentologic interpretations 

based solely on subsurface data in the main area of 

Minnelusa production. 

The upper part of the Minnelusa near Beulah 

consists of dolomite, gypsum (anhydrite in the 

subsurface), and sandstone units deposited in 

transgressive-regressive cycles. Each dolomite records a 

marine transgression across relict eolian-dune 

topography of the previous cycle. The dolomites contain 

a sparse fauna of brachiopods, crinoids, and pelecypods, 
and were probably originally micritic, indicating 

deposition in a low-energy marine environment of 

normal salinity. Gypsum (anhydrite) above the dolomite 

records restriction of the water body as sea level began to 

fall; the gypsum onlapped and then covered the eoliandune sandstones. The fine lamination, thick beds, and 

onlapping relationship to the eolian dunes indicate a 

low-energy subaqueous origin, rather than a sabkha 

origin, for the gypsum. 

Low-energy marine, sabkha, and eolian-dune 

sandstones record continued regression. Marine 

sandstones are uncommon in outcrop, and consist of 

bioturbated to irregularly bedded sandstone with thin 

clay interbeds, suggestive of low-energy conditions. The 

sabkha sandstones consist of wavy-bedded to irregular 

strata formed by algal growth and trapping of sediment 

and possibly by salt-ridge formation, indicating a lowenergy intertidal to supratidal environment of deposition. 

The eolian-dune sandstones record the repeated 

southward movement of a sand sea across the sabkha 

sediments. The extent and distribution of eolian dunes 

differed from cycle to cycle. Where eolian sandstones 

were not preserved, marine and sabkha sandstones are 

directly overlain by marine dolomites of the next cycle. 

The eolian dunes were partially reworked during 

the next cycle's transgression. Eolian ripple strata and 

high-angle sandflow cross-strata of the dune sandstones 

grade laterally into contorted and massive-bedded 

sandstone. In some areas, water-saturated eolian sand 

slumped from the dune to form an apron of reworked 

sand that was subsequently bioturbated. These reworked 

sands indicate that the eolian dunes were not cemented 

prior to the next transgression. 

Dependence of Sandstone Porosity upon 

Thermal Maturity-An Approach to 

Prediction and lnterbasinal 

Comparison of Porosity 

James W. Schmoker and Donald L. Gautier 

Porosity estimation of deeply buried and sparsely 

drilled reservoir rocks is fundamental to hydrocarbon 

exploration. The loss of porosity by burial diagenesis is 

hypothesized here to be, in many sandstone reservoirs, 

principally the result of thermal stress. Data show that 

porosity loss can be described by a power function of the 

form: 

<P = a(M)b, 

where <P is porosity and M is thermal maturity expressed 

as vitrinite reflectance, Lopatin's time-temperature index 

(TTl), or another measure of thermal maturation. 

Basing porosity-decline curves on levels of thermal 

56 

maturation rather than on depth allows direct 

comparison of sandstones of different ages, compositions, and tectonic histories (fig. 1 ). 

The petrologic coefficient a in the above equation 

incorporates the net effect upon porosity of all 

depositional and diagenetic factors, and thus a can vary 

significantly. For example, fine-grained sandstones and 

low values of a are commonly associated, whereas 

extensive secondary porosity is characterized by a high 

value of a. 

The exponent b reflects rate-limiting steps in 

principal mechanisms of porosity loss. In concept, rates 

of porosity loss with thermal maturation could vary 

significantly, but empirical data show that the magnitude 

of b remains within a relatively narrow range. The 

variability of sedimentary and diagenetic processes in the 

natural system appears to be sufficiently limited for 

porosity prediction based on thermal maturation to be 

feasible and useful. 

Offshore Resource Geology of the 

Western United StatesA New Continental Margins Volume 

David W. Scholl, Arthur Grantz, and 

John G. Vedder 

The geologic framework and resource potential 

(hydrocarbon and mineral) of offshore Western North 

America, from the Arctic Ocean to Baja California, 

including the United States Exclusive Economic Zone 

(EEZ) are described in a new continental margins 

volume. The volume contains the results of investigations 

through the last 20 years by USGS and non-USGS 

scientists. Some papers are based primarily on newly 

collected data, and others incorporate previously 

published observations largely recast in light of newer 

data and interpretations, and evolving understanding of 

the structural and stratigraphic history of the continental 

margin. 

The volume is organized into three sections. The 

first section presents the framework geology and 

resource potential of tectonically and geographically 

defined sectors of continental and island-arc margins and 

their bordering shelves. The second section groups 

chapters describing the ocean basins bordering these 

margins. Specific hydrocarbon and mineral resources are 

treated topically in the third section. The regionally 

oriented chapters are arranged in geographic order, 

beginning with the Beaufort Sea in the north and 

progressing southward to the Pacific offshore of Baja 

California. The topical chapters summarize, or provide 

broad exploration perspectives for, a variety of potential 
POROSITY (

0

/o) 

0 3 6 9 12 15 18 21 24 27 30 

4 

• • • • 1.5 5 • , • • • • 

• • • - 6 • Q) • • • , • u; ~ • • ~ 

• • • • 2 Q) 

0 • • Q) 

(/) 7 • E 

0 • 0 • • 0 

0 • • • • (/) 

T""" • • • 0 - 8 •• • 2.5 0 I • • 0 I- • T""" 

a.. • - w 9 • 0 • • Miocene Sands 

• BeKes Basin (Hungary ) 

10 • 3 

• • Cretaceous "J" Sand 

Denver Basin 

11 

3 10 20 30 

3 

10 

• • • •• 

(f) • • !::: • • • z • • ::> •• t= • 

30 

100 

POROSITY (

0

/o) 

Figure 1. Comparison of sandstone porosities from a stable, uplifted foreland basin (Denver 

basin) and a young, hot, extensional basin (Bakes basin, Hungary). Use of thermal maturity 

(TTl) rather than depth as a porosity-prediction parameter permits direct comparison of 

sandstones from diverse tectonic settings. In the lower panel, effects of age, thermal gradient, 

and burial history are incorporated into TTl, and remaining porosity differences between the 

two sandstones reflect petrologic dissimilarities. 

57 
offshore resource commodities. Part of the USGS 

mission is to search out and determine the availability of 

resources that may presently be subeconomic, but which 

the Nation may rely on in the future; many chapters in 

this volume address that mission. 

Pakistan-A Coal-Geologists' Paradigm 

S.P. Schweinfurth, M.J. Bergin, 

W.O. Fredericksen, R.T. Hildebrand, E.R. Landis, 

W.F. Outerbridge, J.F. SanFilipo, F.O. Simon, 

P.O. Warwick, and C. Wnuk 

Coals of Pakistan occur in a varied and fascinating 

array of settings in terms of origin, preservation, quality, 

and rank development. Coals of Paleocene and Eocene 

age occur in relatively flat lying, unexposed subsurface 

deposits as well as in highly folded and thrust-faulted 

terrains. Coals of Permian age (Gondwanian) crop out 

locally in Punjab Province-an area of complex 

structure. Geophysical surveys suggest that additional 

Permian coals may occur in the subsurface, and one 

record exists of deep Permian coal in an oil and gas test 

well. 

Although little is known of the Permian coals, 

enough is known of the Tertiary coals to stimulate great 

interest in their continued study-not just as a 

commodity (which is the principal interest of Pakistan) 

but from a coal-science point of view. Tertiary coals 

apparently formed on the margins of the Indo-Pakistan 

continental plate as it was "sailing" northward to "dock" 

with the Eurasian plate. This inference helps to set the 

regional paleogeography for the origin of these coals and 

aids in initial interpretations of their sedimentologic 

patterns, but the details of each deposit remain a mystery 

and await unraveling by enterprising coal geologists. 

After the collisions of the continental plates, the coal 

deposits were subjected to various amounts of structural 

modification, from simple to severe. 

Although the existence of coal deposits in Pakistan 

has been known for many years and gross estimates of 

coal resources have been reported by the Geological 

Survey of Pakistan (GSP), relatively few details of their 

geology and resource potential appear in the literature. 

Intermittently between 1955 and 1966, USGS personnel 

conducted coal-resource assessment work in Pakistan 

under the aegis of the U.S. Agency for International 

Development (USAID). In 1985, USAID invited the 

USGS to return to Pakistan, to design and monitor a 

coal-resource exploration and assessment program (Coal 

REAP) in southern Sind Province. The objective of this 

ongoing coal exploration program is to demonstrate 

sufficient in-place coal reserves to support the 

development and maintenance of coal-fired electric 

58 

power generation in Pakistan. The task of carrying out 

the assessment fell principally to USGS coal scientists, 

working closely with GSP counterparts as coordinators, 

planners, and teachers. The GSP geologists provide field 

support and knowledge of the terrain. The coal resource 

assessment work is facilitated by drilling wherever 

appropriate, and data from the drill and geophysical logs 

provide the essential third dimension to coal-deposit 

modeling work. 

To 1987, this coal exploration program in Pakistan 

has resulted in the discovery of additional coal resources 

in southern Sind, and USAID has invited the USGS to 

expand Coal REAP studies into two additional provinces, 

Punjab and Baluchistan. If the coal exploration and 

assessment program continues to progress successfully, 

this work may continue for as long as 5 more years. 

Abnormally High- and Low-Pressured 

Oil and Gas ReservoirsExamples from Rocky Mountain Region 

Charles W. Spencer 

Oil and gas reservoirs with abnormally high or 

abnormally low pressures are present in many basins in 

the United States and worldwide. The above-normal 

(overpressured) reservoirs are generally deep ( > 10,000 

ft), are gas bearing, and in onshore basins usually occur 

in low-permeability (tight) reservoir rock sequences. 

Reservoirs with below-normal pressures are mostly 

shallow ( < 10,000 ft), usually contain gas or oil and gas, 

and occur in both tight and permeable (conventional) 

reservoirs. 

Overpressuring in deep, rapidly deposited strata is 

commonly caused by dewatering of shales and siltstones; 

some contribution of pressure also results from clay 

mineral transformations and (or) hydrocarbon 

generation (usually gas). Examples in the United States 

can be found in the Gulf Coast area. Hydrocarbon 

generation is believed to be the primary cause of overpressuring in oil- and gas-producing reservoirs that were 

slowly buried. Slow deposition generally allows sufficient 

time for the shales and siltstones to expel water and to 

compact prior to attaining subsurface temperatures 

sufficiently high for oil and gas generation. This type of 

overpressuring is common in many Rocky Mountain 

basins, where it occurs mostly in rock sequences of 

Cretaceous age, but overpressured oil reservoirs also 

occur in very kerogen-rich rocks of Tertiary and Paleozoic age. 

Abnormally low reservoir pressures seem to be 

caused mostly by gas diffusion and gas shrinkage in 

reservoirs that have been uplifted or otheiWise cooled. 
Recharge of these low-pressure reservoirs by meteoric 

water does not occur rapidly enough to repressure the 

reservoirs to a normal hydrostatic pressure. Shallow 

reservoirs with normal to slightly above normal pressures 

occur in areas where the rocks have better hydraulic 

continuity to recharge areas. Examples of underpressuring can be found in gas-bearing sandstone and carbonate 

reservoirs in the Rockies that range in age from the late 

Paleozoic to Tertiary. 

High pressures in the Rocky Mountain region are 

significant because the overpressured rock sequence is 

deep (hot) and has relatively rich source beds, the 

producing intervals are oil or gas saturated, and discrete 

hydrocarbon-water contacts are generally not present. 

Water production may occur (and it is usually not a 

constraint to production), but the low permeability of the 

reservoir rocks can be a problem. Although hydraulic 

fracturing is commonly used in well completions, natural 

fracturing seems to be necessary for good production 

rates and ultimate recovery. Classical hydrodynamic 

concepts are not applicable to overpressured intervals in 

the Rockies. The optimum depths for exploration are 

generally the upper 1,000-2,000 ft of the overpressured 

rock sequences. Improved prices and completion 

methods would be needed to make deep, overpressured 

wells more economic. 

A Major Eocene Suture in the 

Southern Washington Cascades-Are 

Hydrocarbon Source Rocks 

Buried Beneath Volcanic Flows? 

Dal Stanley, Bill Heran, and Carol Finn 

Deep geophysical studies have been carried out in 

the western half of Washington and portions of western 

Oregon, relying primarily upon magnetotelluric (MT) 

soundings to locate undetected sedimentary rocks that 

could serve as hydrocarbon sources. These studies have 

been designed to locate any sedimentary basins or 

complexes lying beneath the extensive Tertiary and 

Quaternary volcanic flows and oceanic crustal rocks west 

of the Cascade Mountains in Oregon and Washington. 

Although hydrocarbon exploration has been relatively 

active in the Columbia Basin of eastern Washington, the 

only successful hydrocarbon production has been from 

the Mist Gas Field region west of Portland, Oregon. In 

the region west of the Cascades in Oregon and 

Washington, several distinct forearc basins have been 

explored, including the Astoria, Gray's Harbor, Chehalis, 

and Willamette Basins. All these basins contain 1-5 km 

of Eocene marine sediments with low maturation indices. 

The Mist Gas Field lies east of a saddle between the 

59 

Astoria and Willamette Basins; geochemical analyses of 

the gases from the field imply a deeper origin for the gas 

than can be provided by sediments from the nearby 

basins. 

Extensive MT surveys in Washington and Oregon 

have been interpreted to postulate the existence of very 

thick marine sediments in a proposed suture zone in the 

southern Washington Cascades. This hypothesis is based 

upon the occurrence of a mapped highly conductive body 

with resistivities of 1-5 ohm-m and thicknesses of 5-15 

km. The conductive body dips to the east; it is bounded 

by accreted seamount complex and other oceanic crustal 

rocks on the west and resistive, possibly continental crust 

on the east. Four lithologies have been evaluated as 

possible causes of the high conductivity anomaly; in the 

preferred model for the feature, an early Eocene forearc 

basin containing 5-7 km of marine sediments was 

compressed and partially subducted during accretion of 

the extensive seamount complex that makes up the Coast 

Ranges of Oregon and Washington. Other geophysical 

and geological data support the preferred model. 

The shallowest portions of the conductor correlate 

with outcrops of transitional marine units in the lower 

part of the Puget Group in the Carbon River anticline 

west of Mount Rainier. Tectonic reconstructions suggest 

that, whereas the upper part of the conductor may be 

composed of such Eocene marine sediments, part or 

most of the conductor could consist of Paleocene or older 

sediments. 

Possible source and reservoir implications of this 

geophysical anomaly have been considered, and relations 

to nearby known basins, such as the Chehalis Basin, have 

been evaluated; important research for the future 

includes surface geochemical studies and completion of a 

deep reflection profile. This model is important not just 

for evaluation of hydrocarbon potential for the region: 

the suture zone between the accreted seamount complex 

and the proposed marine basin may control the location 

of a seismically active strike-slip zone that passes through 

Mount St. Helens and may thus provide a key constraint 

in the location of the volcano itself. The studies were 

supported by the Department of Energy, Morgantown 

Energy Technology Center. 

Eocene Lava and Epigene 

Mineralization Alter Alaska's 

Thickest Known Coal Deposit 

Gary D. Stricker and Ronald H. Affolter 

Alaska's thickest known coal accumulated in the 4 

square mile tectonic Boulder Creek basin in Death 

Valley, southeastern Seward Peninsula, Alaska. Bedrock 
in the area consists of Precambrian(?) and Paleozoic 

metamorphic rocks that were intruded in the Late 

Cretaceous by acid magmas resulting in the formation of 

alkalic monzonitic plutons. Post-intrusive faulting 

formed the Boulder Creek graben, which filled with 

sediments and organic debris. An 80-foot-thick Eocene 

basaltic lava flowed into a thick peat swamp, 

catastrophically ending organic accumulation. 

Subsequent epigenetic mineralization began after 

deposition of the host sediments and has continued to the 

present. The geochemical effects of lava and epigenetic 

mineralization in Death Valley make this coal deposit 

unique. 

Exploratory core holes in the graben, drilled for 

uranium, contained three coal beds, with one bed 

exceeding 165 ft thick. Chemical analyses were 

determined on six vertical increments of the thick coal 

from two core holes, and vitrinite reflectance was 

determined on 20 random samples taken throughout this 

coal. 

Mean random vitrinite reflectance values are 0.4 

Ro percent at the base and 2.6 Ro percent at the top. 

Total sulfur content ranges from 0.38 to 1.5 percent with 

the highest value near the base of the bed. Ash content is 

variable from 2.3 to 6.8 percent. Significant enrichment 

in the contents of Cu, F, Hg, K, Li, Mg, Na, Ni, Pb, and 

Sr occurs within the top 35 ft of the coal bed. These 

elements were mobilized in the basalt by steam produced 

by the violent reaction of lava entering the wet peat 

swamp. 

Uranium content of 37 ppm (whole coal) in the 

basal 30 ft of the coal represents an enrichment of 30 

times the average for other United States coals. Uranium 

was derived from the nearby plutons and concentrated in 

the base of the coal during and after peat accumulation 

by epigenetic mineralization. The basalt may have acted 

as a barrier to these mineralizing fluids, thereby 

minimizing the enrichment of uranium at the top of the 

bed. Death Valley coal has the highest reported content 

of tungsten (360 ppm whole coal) for any United States 

coal. A linear correlation of 0.95 between uranium and 

tungsten suggests that the epigenetic mineralization 

phase which concentrated uranium also concentrated 

tungsten. 

Apparent rank increases from subbituminous C 

near the coal's base to semianthracite at the top. This, 

coupled with high tungsten and uranium content, makes 

the Death Valley deposit different from other Alaskan 

and United States coals. Intense heat over a relatively 

short time interval and epigenetic mineralization are the 

major factors affecting rank and element distribution in 

this coal and warrant further investigation. 

60 

Overthrusting in the 

Northwestern San Juan Basin, 

New Mexico-A New Interpretation of the 

Hogback Monocline 

David J. Taylor and A. Curtis Huffman, Jr. 

The Hogback monocline is a prominent northeasttrending structure that bounds the northwestern edge of 

the San Juan Basin. Multichannel seismic reflection lines, 

shot at various angles to the monocline in the vicinity of 

Waterflow, New Mexico, reveal a series of complex faults 

at depth. The seismic data together with selected 

adjacent well data have allowed us to locate the major 

faults, identify the type of faulting involved, and 

determine the movement along the faults over time. 

Domal structures genetically related to the observed 

faulting are major hydrocarbon producers in this part of 

the San Juan Basin. (See sketch, fig. 1.) 

Twelve-fold CDP seismic reflection lines and 

geophysical well logs provided the primary information 

input to this investigation. Six stratigraphic boundaries 

were identified from the well logs and were correlated 

with the seismic data through the use of synthetic seismograms. Interval velocity data used in converting the 

picked time horizons to depth were established from 

acoustic and resistivity logs from all sides of the major 

faults. 

These data yield a pattern of intersecting 

northeast- and northwest-trending faults of probable 

Precambrian ancestry. These faults display a complex 

history of movement. For example: 

1. Northwest-trending faults exhibit vertical 

components of movement from early Paleozoic 

through at least Triassic time. 

2. High-angle reverse faulting and significant thrusting 

during the Laramide are evident on both northwest 

and northeast faults including northeast-, southeast-, 

and southwest-directed thrusting. 

The observed fault pattern was most likely 

inherited from Precambrian orogenic movements. 

Thickness variations between northwest-trending blocks 

indicate vertical movement along a northwest -trending 

fault zone during the Paleozoic and early Mesozoic. 

During the Laramide, general east-west shortening 

resulted in right-reverse movement along the northeasttrending fault zone, left-reverse movement along the 

northwest-trending zone, and transpression in the area of 

intersection that produced concurrent overthrusting in 

several directions, forming the Hogback monocline and 

related hydrocarbon-rich domal structures. 
DISTANCE (FEET x 1 000) 

2 

-0 

.o 

0 

..... 

JC 

.... 

w 

w 

u. 

8 

% 

.... 9 G. 

w 

Q 10 

1 1 

12 

13 

4 6 

' 

TRIASSIC 

PERMIAN 

8 

PENNSYLVANIAN 

PRECAMBRIAN 

10 12 14 16 

r 

18 

I 

NE 

20 

I 

JURASSIC 

TRIASSIC 

PERMIAN 

PENNSYLVANIAN 

PRECAMBRIAN 

22 

Figure 1. Depth-converted seismic data across Hogback monocline showing thrust faulting and related domal structure. 

Tectonic History and 

Petroleum Potential of 

Eastern Washington and Oregon 

Marilyn E. Tennyson and Judith Totman Parrish 

Petroleum resource assessment in the Pacific 

Northwest east of the Coast Range is complicated by 

extensive Cenozoic volcanic cover. Analysis of tectonic 

history is one approach to characterizing potentially 

prospective sedimentary sequences and attempting to 

deduce their distribution beneath volcanic rocks. 

Evaluation of this region for the Federal Lands 

Assessment Program was based on integration of 

regional history with lithologic and stratigraphic data 

from outcrops and drill holes. Two sequences with some 

potential are an Upper Cretaceous marine section in 

Oregon and an Eocene fluvial sequence in central 

Washington and northern Oregon. 

Allochthonous terranes in the Klamath and Blue 

Mountains of Oregon comprise Paleozoic and Mesozoic 

ophiolitic, subduction-complex, and arc rocks formed at 

southerly latitudes. Unconformably overlying AlbianMaastrichtian marine clastic rocks 4,000-8,000 ft thick 

(Ochoco, Mitchell, and Hornbrook sequences) 

61 

demonstrate that the allochthonous terranes were in 

place by Albian time, then partially covered by detritus 

eroded from accretion-related uplifts. Eastern 

Washington lacks an analogous Upper Cretaceous postaccretion marine sequence. 

The Eocene continental margin was characterized 

by oblique convergence between North America and the 

Kula plate. Calc-alkaline volcanism and right-lateral 

faulting took place east of newly accreted Coast Range 

basaltic basement. Crustal extension in Washington, 

British Columbia, and Idaho was associated with unroofing of crystalline rocks, which provided large volumes of 

arkosic detritus. The resulting sediments accumulated to 

more than 20,000 ft in strike-slip basins in central 

Washington and 0--2,000 ft in fluvial systems in Oregon, 

apparently outside fault-controlled basins. Cascade arc 

volcanism began in Oligocene time and has continued 

through the Neogene. In Miocene time, the Columbia 

River Basalt Group erupted from fissures in easternmost 

Washington and Oregon, flowed down west -sloping 

dissected topography, and lapped onto the Cascade arc. 

Episodic deformation accompanied volcanic activity. 

In Oregon, gas-or less probably, oil-could have 

been generated from mostly Type III organic matter in 

the Cretaceous sequence or from organic-rich or coaly 
intervals in the Eocene fluvial sequence. Eocene arkosic 

sandstones have adequate reservoir characteristics, but 

Cretaceous sandstones do not. Widely scattered wells 

reveal marked lateral stratigraphic variation in the 

Cretaceous and Eocene sequences: both are widespread, 

but each is also locally absent, and thicknesses vary. In 

only a few localities are both Eocene and Cretaceous 

rocks present, but because Eocene fluvial sediments 

were probably deposited on a subcrop surface consisting 

of both accreted terranes and overlying Upper 

Cretaceous rocks, it seems possible that both sequences 

coexist beneath volcanic cover. 

In central Washington, drilling has shown that the 

Eocene fluvial sequence continues beneath Miocene 

basalt and that it contains some gas. Lacustrine mudstone and coal, potential source rocks, are present in this 

section where it is exposed around the perimeter of the 

basalt. Lopatin modeling based on published vitrinite 

reflectance data suggests that burial by basalt in middle 

Miocene time caused maturation of the Eocene section. 

Porosity in samples from recent drill holes varies but is 

reported to be adequate (13-16 percent) in tested stratigraphic intervals. Quantities of gas and condensate 

tested in wells drilled so far are insufficient to offset the 

costs of drilling through basalt 5,000-11,000 ft thick. 

Low-Temperature Formation of 

Illite-Implications for 

Clay Geothermometry and 

Hydrocarbon Generation 

Christine E. Turner-Peterson, 

Neil S. Fishman, and Douglass E. Owen 

Diagenetic illite/smectite in sedimentary rocks is 

used widely as a geothermometer in evaluating the 

thermal history of potential hydrocarbon-bearing 

sequences. The conversion of smectite to illite/smectite is 

generally thought to begin when temperatures reach 90 

°C. Thus, the conversion is used as a geothermometer to 

determine if a sedimentary sequence has been buried to 

sufficient depths to have generated hydrocarbons. The 

conversion itself has also been linked to the generation 

and expulsion of hydrocarbons. Moreover, the 

conversion frees abundant fresh water, which can lead to 

abnormally high fluid pressures in fine-grained rocks; 

these fluid pressures are used throughout the petroleum 

industry as keys to hydrocarbon production. 

Use of diagenetic illite/smectite as a geothermometer stems largely from analogies with the Tertiary 

section of the Gulf Coast, where the proportion of illite 

layers in illite/smectite clay increases with increasing 

burial depth. Recently, however, it is increasingly 

62 

apparent that the Gulf Coast model cannot explain all 

occurrences of illite/smectite in sedimentary rocks and 

that pore-water chemistry may be more significant than 

temperature in certain cases. Pore-water chemistry has 

been acknowledged as an important constraint for this 

reaction because a source of potassium is required, but it 

has not generally been thought that pore-water chemistry 

alone can facilitate the conversion from smectite to 

illite/smectite in the absence of elevated temperatures. 

(Whether authigenic illite/smectite can precipitate 

directly from solution is unclear.) 

Saline, alkaline lakes, because of their extreme 

pore-water chemistry and hydrogeochemical zonation, 

are an appropriate setting to evaluate the role of porewater chemistry in the formation of clay minerals. Some 

workers have suggested that the pore-water chemistry of 

saline, alkaline lakes might be conducive to the formation 

of illite at low temperatures ( < 90 oc). Saline, alkaline 

lake deposits in the Brushy Basin Member of the Jurassic 

Morrison Formation, Colorado Plateau, provided a 

natural laboratory to test this hypothesis. 

In this study, analyses of clay separates from tuff 

beds reveal a pattern of increasing illite content in the 

illite/smectite (in stratigraphically equivalent intervals) 

toward the center of the lake. This trend in clay mineral 

composition coincides with the systematic basinward 

change from authigenic zeolites to feldspars, a change 

which reflects a steep hydrogeochemical gradient, with 

inferred salinities and alkalinities of the pore waters 

increasing toward the center of the lake. Randomly 

interstratified illite/smectite clay (80-100 percent smectite layers) occurs either as the predominant mineral or 

with clinoptilolite in the two outermost lake facies. In 

contrast, ordered illite/smectite (0-30 percent smectite 

layers) occurs in association with authigenic albite in the 

central lake facies. Mixed-layer illite/smectite of highly 

variable composition (20-80 percent smectite layers) 

occurs with analcime and authigenic potassium feldspar 

in the intervening lake facies. The absence of illite in the 

two outermost lake facies precludes a detrital origin for 

the illite in the more central facies. 

The way in which composition of mixed-layer 

illite/smectite mimics the zonation of early authigenic 

aluminosilicates (zeolites and feldspars) across the lake 

strongly suggests a pore-water control on clay mineral 

composition. We therefore infer a low-temperature, 

near-surface origin for the illite in contrast to the hightemperature ( > 90 °C), deep burial conditions required 

by the Gulf Coast model of illite formation. As a result, 

caution should be exercised when illite is used as a 

geothermometer to evaluate the thermal evolution of 

sedimentary sequences. 
Submarine Canyons of the 

Florida Escarpment, 

Eastern Gulf of Mexico 

D.C. Twichell and L.M. Parson' 

GLORIA (Geologic LOng Range Inclined Asdic) 

sidescan sonar images correlated with Sea Beam bathymetric data show that the Florida Escarpment, a steep 

carbonate cliff off western Florida, is incised by two 

different types of canyons. North of lat 27° N., canyons 

are narrow and straight, are spaced 3-8 km apart, and are 

fed by dendritic tributaries. These canyons extend from 

near the top of the escarpment to its base; some have 

small fans extending from their mouths. South of lat 27° 

N., large, flat-floored, and steep-sided box canyons 

deeply incise the escarpment and the West Florida Slope 

above the escarpment. These canyons are as much as 10 

km wide; they are spaced 10-25 km apart and have nearly 

vertical head walls. Slumps on the West Florida Slope 

mostly feed into the box canyons. 

The morphological differences between these two 

groups of canyons suggest different canyon-forming 

processes and variations in the erosional mechanisms 

that have operated along the length of the escarpment. 

The morphology of the northern type of canyons and of 

the fans at their bases suggests formation by downslope 

transport, whereas the box canyons are similar in 

appearance to canyons on land that have been attributed 

to undercutting by ground-water sapping. Evidence of 

ground-water discharge along the base of the escarpment 

has been found in localized areas south of Iat 27° N., 

suggesting that sapping could have contributed to the 

development of the box canyons. 

Geology and Petroleum Resources of the 

Barents-Northern Kara Shelf, 

U.S.S.R. and Norway 

Gregory Ulmishek 

The Barents-northern Kara shelf, one of the 

largest continental shelves in the world (2,450,000 km2

), 

is still in the earliest stage of exploration for oil and gas. 

Small-scale gravity and magnetic surveys provide the only 

data on the geology of large central areas of the shelf. 

Some seismic surveys and wildcat drilling have been 

conducted mainly along the western and southern 

margins. Geologic interpretation is based on these data, 

1

Institute of Oceanographic Science, Wormley, U.K 

63 

as well as on extrapolation of the stratigraphy and 

tectonics known onshore and on islands. 

The pre-Late Devonian geology of the shelf is most 

uncertain. It appears that large transcurrent movements 

of continental blocks took place during and after the 

Caledonian orogeny. However, the common view that the 

shelfs basement is of Caledonian age is probably 

incorrect, and large areas may have a thick, undeformed 

lower Paleozoic section. 

The Upper Devonian through Permian section is 

composed mainly of carbonate facies. The development 

of reefal buildups and associated black-shale facies may 

be predicted in a system of Paleozoic troughs stretching 

along the Norwegian shore and Kola Peninsula. Permian 

molasses derived from the Uralian Hercynides are not 

expected to extend far offshore. 

The geology of a very thick (possibly 6-8 km) 

Triassic sequence is a key to evaluation of the region's 

petroleum potential. Correlation of Triassic rocks 

exposed and drilled on the shelf margins indicates the 

existence of a large sedimentary paleobasin covered by 

deep-water, black-shale facies of Middle Triassic age. 

This facies is presently known only on eastern Svalbard 

Archipelago, Norway; it is an excellent oil-source rock 

that is probably mature to overmature over most of the 

shelf. 

Another potential source-rock interval is present at 

the top of the Upper Jurassic section. Black organic-rich 

shales here are the stratigraphic and facies analog of the 

oil-source Kimmeridgian shale of the North Sea and the 

Bazhenov shale of West Siberia. On the Barents shelf, 

however, these shales are probably immature, except in a 

few local depressions. 

The present-day regional structural framework of 

the Barents shelf consists of deep basins along southern 

and eastern margins, and a generally uplifted area on the 

west and north. The most important basins are the 

Finnmark trough of mainly late Paleozoic age, and the 

South Barents and North Novaya Zemlya depressions, 

which are filled with very thick Upper Permian-Triassic 

clastics. These basins have the most interesting 

exploration potential. Other exploration targets are the 

late Mesozoic Tromso-Bjornoya rift in the southwestern 

part of the shelf and the offshore continuation of the 

Paleozoic Timan-Pechora basin on the southeast. 

Several gas fields with total reserves of 5 to 10 

trillion cubic feet and one noncommercial but 

geologically significant oil field have been discovered in 

the Norwegian part of the shelf. An important oil and 

gas-condensate field is being developed on the U.S.S.R.'s 

Kolguyev Island. 

Geologic interpretation indicates high hydrocarbon 

potential for the Barents-northern Kara shelf, but also 

implies a significantly gas-prone character of the region. 

This emphasis on gas does not imply that rich oil plays 
cannot be found, but such plays will probably not be 

abundant. Development of gas fields in this remote polar 

region will not be economic for a long time; therefore, 

the main goal of future exploration will be to determine 

the combination of geologic factors that favor formation 

of oil versus gas accumulations. 

Stratigraphy and Facies Analysis of 

Tertiary Units, Western Medicine Lodge 

Basin, Montana 

Jean N. Weaver 

Medicine Lodge Basin, in southwestern Montana, 

is an intermontane basin bordered on the south and west 

by the Bitterroot Range and on the east and north by the 

Tendoy and Pioneer Mountains. Basin deposits consist of 

as much as 9,900 ft of Eocene(?) to Miocene volcanic and 

sedimentary rock units. This study focused on the Oligocene(?) to lower Miocene(?) part of the sedimentary 

sequence. Stratigraphic and facies analyses of these 

Tertiary rocks resulted in recognition of three 

stratigraphic-facies units: a conglomeratic facies, which 

interfingers to the south with a coal-bearing facies, and 

an overlying platy shale facies. 

The conglomeratic facies (up to 1,350 ft thick) is 

framework supported in the northern portion of the 

study area and matrix supported in the southern part. 

The principal internal structure of this unit is a series of 

en echelon conglomerate deposits, each one averaging 5 

ft in length and 2 ft in thickness. Tertiary volcanic rocks 

and Precambrian quartzites make up the majority of the 

clasts, which are subangular to rounded, varying in size 

from pebbles to cobbles, some 8 in. in diameter. Crude 

pebble imbrication is visible. Towards the middle of the 

Medicine Lodge Peak as viewed from Keystone Gulch, 

Medicine Lodge Basin, Montana. 

64 

facies, conglomerate deposits are overlain by mediumgrained 2-5 ft thick sandstone bodies, many of which are 

trough crossbedded. Conglomerate clasts are found at 

the base of these sandstone bodies. 

The coal-bearing facies consists of alternating beds 

of sandstone, siltstone, shale, carbonaceous shale, and 

coal. The sandstone bodies (up to 6 ft thick), some with 

erosional bases, are fine to medium grained and display 

either trough crossbeds or ripple marks over 

conglomeratic lag deposits. Occasional plant fragments 

or root marks are present. Light-yellow siltstones, often 

plant rich, are found interbedded with medium-gray 

mudstones and shales (up to 5 ft thick). The less resistant 

shale units grade into either the overlying or underlying 

carbonaceous shale or coal beds. Carbonaceous shale 

beds (averaging 0.5 ft in thickness) are dark brown; many 

weather out as resistant ledges. Carbonaceous shale beds 

are also found as lenticular stringers within the coal beds, 

displaying gradational upper and lower contacts. Coal 

beds, lenticular in nature, can attain 5 ft in thickness. 

The platy shale facies consists of tuffaceous, fissile 

brown shale that tends to weather white in resistant 

ledges. Fish, ostracodes, and plant fossils of middle 

Oligocene age are present throughout the facies. 

Limestone stringers are associated with this facies. 

The conglomeratic and coal-bearing facies show a 

lateral change from the northern part of the study area 

down towards the south. The conglomeratic facies, which 

represents a very coarse clastic wedge, splits and interfingers with the coal-bearing facies to the south. The 

conglomeratic deposits and associated sandstone bodies 

represent deposition in a high-energy fluvial system. 

However, the sandstones are interpreted to be deposits 

of a low-energy fluvial system. The coal-bearing facies 

represent deposition in a fine-grained fluvial system. 

Associated with this latter system is a poorly drained 

floodplain in which coal and carbonaceous shale beds 

were deposited in detritus-free swamps. The overlying 

platy shale facies represents a freshwater lake. This shale 

facies, laterally extensive in the northern portion of the 

study area, is also present as thin units in the coal-bearing 

deposits in the south. 

Detailed studies of these Tertiary deposits provide 

facies patterns of deposition of coal beds in Medicine 

Lodge Basin. Understanding their environments of 

deposition may assist in understanding coal accumulation in other Tertiary intermontane basins in 

southwestern Montana and northeastern Idaho. 

Indigenous Sources of Fossil Fuels, 

Sahel Region of North Africa 

Jean N. Weaver, Marion J. Bergin, Michael E. 

Brownfield, and Edwin R. Landis 

The Sahel region, in north-central Africa, is located 
between the Tropic of Cancer and the Equator. Mauritania, Senegal, Mali, Burkina, Niger, Togo, Benin, 

Nigeria, Chad, Cameroon, Central African Republic, 

Sudan, Ethiopia, Rwanda, Burundi, and Tanzania are all 

within or adjacent to the Sahel region. 

Occurrences of coal and (or) peat have been 

reported in all the Sahel countries except Burkina, Togo, 

Chad, and Uganda. Even in these latter countries, coal or 

peat deposits may exist, because neighboring countries 

contain coal-bearing rocks. Senegal, Niger, and Nigeria 

are the only countries in which coal or peat is actively 

mined. Coal is being used to generate electrical power as 

well as to supply some domestic heat and fuel; peat can 

be used as a fuel source, and has been used already in 

agriculture as a soil amendment. The primary domestic 

fuel source for these countries is wood charcoal; 

deforestation, overgrazing, nomadic cultural changes, 

and climatic changes, all linked to extended drought and 

desertification, have contributed to a severe wood 

charcoal shortage. This shortage suggests a real need to 

identify and develop indigenous fossil fuels in the Sahel 

countries. A concentrated study of the coal (lignite and 

higher rank) and peat occurrences within this region 

could identify a much needed alternative fuel source for 

the countries' economies. 

Potential coal resource areas have been defined, 

using topographic and geologic parameters. Ten 

sedimentary basins have been identified from the 

literature: (1) Somali Basin, (2) Plateau and rift belt, (3) 

Sudan Trough, (4) Chari Basin, (5) Chad Basin, (6) 

Niger Basin, (7) Benue Trough, (8) Taoudeni Basin, (9) 

Senegal Basin, and (10) Gao Trough. Exposed Precambrian basement rocks surround most of these basins. 

From our preliminary studies, the potential for finding 

economic coal and (or) peat deposits within these basins 

appears to be high. 

The economic and agricultural sectors of the Sahel 

region countries could greatly benefit from the 

development of indigenous fossil fuels. Use of fossil fuels 

may decrease or even halt the rate of desertification. 

Locating coal and peat deposits and evaluating their uses 

would help the countries' economic development, 

allowing them to become more self sufficient and less 

dependent on foreign energy resources. 

Paleobotanical Composition of 

Some Pennsylvanian Coal Beds from the 

Central Appalachian Basin as an 

Indication of Paleoclimate 

Richard B. Winston and Ronald W. Stanton 

The abundances of peat-forming plant groups were 

quantified in a study of polished and etched blocks of 

65 

coal, to help interpret climate changes during the 

Pennsylvanian Period in the central Appalachian basin. 

Floras were identified in 18 columnar samples from 13 

coal beds that range stratigraphically from the Pocahontas No.2 to the Pittsburgh. 

Lycopods are most abundant (54-70 percent of 

botanical content) in the coal beds of the Pocahontas and 

New River Formations (Lower Pennsylvanian) and less 

common ( 42-46 percent) in the Upper Banner through 

Eagle coal beds of the lower part of the Kanawha 

Formation (Middle Pennsylvanian). Lycopods again 

reach high abundance (55 percent) in the Campbell 

Creek coal bed (Kanawha Formation) and then gradually 

decrease (35-55 percent) through the rest of the coal 

beds in the Kanawha Formation and Charleston 

Sandstone (Middle Pennsylvanian). Coal beds in the 

Conemaugh Formation were not investigated, but lycopods reached their lowest abundance (11 percent of 

botanical content) in the Pittsburgh coal bed of the 

Monongahela Formation (Upper Pennsylvanian). Pteridosperms, the other statistically important constituent, 

increase in abundance only in places where the beds are 

split by partings or where the beds thin. 

Lycopods are interpreted to have been most 

abundant under the wettest conditions; their abundance 

has been used by previous workers as an index of relative 

''wetness" at least during the Lower and Middle 

Pennsylvanian. Our study indicates that the climate was 

wettest during the Early Pennsylvanian and became less 

wet during the early part of the Middle Pennsylvanian. 

Then, the climate abruptly became wetter in the middle 

of the Middle Pennsylvanian Series followed by gradual 

drying throughout the remainder of the Middle 

Pennsylvanian. The lycopods, which had formed much of 

the peat in the Lower and Middle Pennsylvanian, were 

becoming extinct during the Late Pennsylvanian; their 

ecological niche was being occupied by other groups, 

primarily ferns. Therefore, the abundance of lycopods 

cannot be used to compare the relative wetness during 

the formation of the Pittsburgh peat to the wetness of the 

Early and Middle Pennsylvanian. 

Another explanation for the decrease in lycopod 

abundance through time-besides relative wetness-is 

that other plants were evolving greater tolerance for the 

environmental conditions of the swamps. Such an 

explanation would apply only to the gradual decrease in 

lycopods in the upper part of the Kanawha Formation 

through the top of the Charleston Sandstone. However, 

pteridosperms and ferns had already reached levels of 

abundance in the lower part of the Kanawha Formation 

as great as those found at the top of the Charleston 

Sandstone-so evolution probably does not explain these 

results. 

In the abundance profiles of the columnar bed 

samples, two common patterns of lycopods abundance 
were observed: (1) lycopods decreasing in abundance 

toward the top of the coal bed, and (2) no correlation 

between position in the coal bed and lycopod abundance. 

The first pattern was found primarily in beds in the New 

River and the lower part of the Kanawha Formation, 

whereas the second pattern occurs throughout the 

66 

section. Other less common patterns show pteridosperms 

increasing upsection within coals beds of the Lower 

Pennsylvanian and the lower and upper part of the 

Middle Pennsylvanian. The two major patterns of peat 

formation may also indicate differences of climate of the 

central Appalachian basin during the Pennsylvanian. 
ORGANIZATION OF THE U.S. GEOLOGICAL SURVEY 

Office Name Telephone City 

Office of the Director 

Director Dallas L. Peck 703/648-7411 Reston 

Associate Director Doyle G. Frederick 703/648-7412 Reston 

Assistant Director for Research Bruce R. Doe 703/648-4450 Reston 

Assistant Director for Engineering Geology James F. Devine 703/648-4423 Reston 

Assistant Director for Administration Jack J. Stassi 703/648-7200 Reston 

Assistant Director for Programs Peter F. Bermel 703/648-4430 Reston 

Assistant Director for Intergovernmental Affairs John J. Dragonetti 703/648-4427 Reston 

Chief, Public Affairs Office Donovan B. Kelly 703/648-4459 Reston 

Assistant Director for Information Systems James E. Biesecker 703/648-7108 Reston 

National Mapping Division 

Chief Lowell E. Sta~ 703/648-5748 Reston 

Geologic Division 

Chief Geologist Benjamin A. Morgan 703/648-6600 Reston 

Water Resources Division 

Chief Hydrologist Philip Cohen 703/648-5215 Reston 

ORGANIZATION OF THE GEOLOGIC DIVISION 

Office of the Chief Geologist 

Chief Geologist Benjamin A. Morgan 703/648-6600 Reston 

Associate Chief Geologist William F. Cannon 703/648-6601 Reston 

Assistant Chief Geologist for Program David P. Russ 703/648-6640 Reston 

Assistant Chief Geologist, Eastern Region Jack H. Medlin 703/648-6660 Reston 

Assistant Chief Geologist, Central Region Harry A. Tourtelot 303/236-5438 Denver 

Assistant Chief Geologist, Western Region Carroll Ann Hodges 415/329-5101 Menlo Park 

Office of Mineral Resources 

Chief Glenn H. Allcott 703/648-6100 Reston 

Chief, Branch of Alaskan Geology Donald J. Gcybeck 9071786-7403 Anchorage 

Chief, Branch of Eastern Mineral Resources Bruce R. Lipin 703/648-6327 Reston 

Chief, Branch of Central Mineral Resources David A. Lindsey 303/236-5568 Denver 

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Chief, Branch of Sedimentary Processes Thomas D. Fouch 303/236-1644 Denver 

Chief, Branch of Pacific Marine Geology Monty A. Hampton 415/329-3184 Menlo Park 

Chief, Branch of Atlantic Marine Geology Robert B. Halley 617/837-4211 Woods Hole 

67 
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68 

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U.S. Geological Sutvey 

Quissett Campus, Building B 

Woods Hole, MA 02543 
AUTHOR INDEX 

A Elston, D.P .................................................................................................. 49 

Affolter, R.H .......................................................................................... 6, 59 Englund, K.J ................................................................................................ 16 

Agena, W.F ............................................................................................. 3, 28 

Anders, D .E .......................................................................................... 24, 44 

Finkelman, R.B .................................................................................... 16, 39 

Finn, Carol. .................................................................................................. 59 

Arthur, M.A .......................................................................................... 10, 20 Fishman, N.S ............................................................................................... 62 

Attanasi, E.D ................................................................................... 1, 14, 31 Fletcher, J.D ................................................................................................ 44 

Fox, J.E .......................................... , ............................................................. 55 

B Fredericksen, W.O .... , ................................................................................ 58 

Ball, M.M ..................................................................................................... 48 

Barker, C.E .................................................................................................... 1 G 

Bayer, KC ...................................................................................................... 2 Gajdos, I. ..................................................................................................... 37 

Behrendt, J.C ............................................................................................ 3, 7 Gardner, J.V ................................................................................................ 14 

Berczi, I. ....................................................................................................... 37 Gautier, D.L ......................................................................................... 20, 56 

Bergin, M.J ...................... , .................................................................... 58, 64 Ghiorse, W.C ............................................................................................... 53 

Bird, KJ ..................................................................................................... 4, 9 Gibbons, A.B .............................................................................................. 22 

Bohannon, R.G ........................................................................................... 14 Grantz, Arthur .............................. , ............................................................. 56 

Bostick, N.H .................................................................................................. 4 Green, A.G ............................................................................................... 3, 7 

Bragg, LJ ..................................................................................................... 39 Greene, H.G ................................................................................................ 17 

Brownfield, M.E .............................................................................. 6, 33, 64 Grow, J.A .............................................................................................. 18, 36 

Bultman, M.W ............................................................................................... 6 

Burnett, W.C ............................................................................................... 40 H 

Burruss, R.C ................................................................................................ 48 Hansen, D .E ................................................................................................ 33 

Hatcher, P.G ............................................................................................... 18 

c Heran, Bill ................................................................................................... 59 

Cannon, W.F ............................................................................................. 3, 7 Herring, J .R ................................................................................................. 20 

Carlson, P.R ................................................................................................ 14 Hettinger, R.D ............................................................................................ 33 

Carter, M.D ................................................................................................. 15 Higley, D.K .................................................................................................. 20 

Cecil, C.B ................................................................................................. 8, 37 Hildebrand, R.T .......................................................................................... 58 

Charpentier, R.R ................................................................................. 27, 31 Hinrichs, E.N ................................................................................. 18, 21, 36 

Chin, P .......................................................................................................... 40 Holmes, C.W ............................................................................................... 22 

Clayton, J.L ............................................................................................. 9, 27 Huffman, A.C., Jr ....................................................................................... 60 

Cobb, J.C ................................................................................................. 8, 15 Huggett, 0 ................................................................................................... 14 

Coleman, S.L ............................................................................................... 39 Hunter, R.E ............................................................................................... 14 

Collett, T.S ..................................................................................................... 9 Hutchinson, D.R ............................................................................ 3, 25, 28 

Cooper, A.K ................................................................................................ 14 

Crovelli, R.A .................................................................................. 23, 27, 31 

Crowley, S.S ................................................................................................. 10 

1-K 

Isaacs, C.M ................................................................................................. 22 

Johnson, E.A ............................................................................................... 47 

D Johnson, R.C .............................................................................................. 23 

Daws, T.A ...................................................................................................... 9 Johnson, S.Y ......................................................................................... 24, 38 

Dean, W.E ............................................................................................. 10, 20 Juhasz, Gy. K ............................................................................................ 37 

de Vrind, E.W ................................................. , ........................................... 53 Karl, H.A ..................................................................................................... 14 

de Vrind, Hans .......................................................... , ................................ 53 Keighin, C.W .................................................................. , ............................ 51 

Dillon, W.P ........................................................................................... 13, 52 Kenyon, N.H .............................................................................................. 14 

Dobson, M.P ............................................................................................... 14 King, J.D ........................................................................................... 9, 25, 44 

Dolton, G.L .......................................................................................... 27, 31 Kirschbaum, M.A ...................................................................................... 33 

Drew, L.J ..................................................................................................... 14 Klitgord, K.D ............................................................................................... 25 

Dulong, F.T ................................................................................................... 8 Kotra, R.K .................................................................................................. 26 

Kovacs, A ..................................................................................................... 37 

E,F 

Eble, C.F ...................................................................................................... 37 L 

Edgar, N.T ................................................................................................... 13 Landing, W ................................................................................................. 40 

Edwards, B.D .............................................................................................. 14 Landis, E.R ........................................................................................... 58, 64 

EEZ-Scan Bering Sea and Aleutian Arc Groups ................................ 14 Law, B.E ...................................................................................................... 27 

Eggleston, J.R ............................................................................................. 15 Lee, K.Y ....................................................................................................... 28 

69 
Lee, M.W ............................................................................. 3, 18, 28, 36, 55 Robb, J.M .................................................................................................... 52 

Lerch, H.E., III ........................................................................................... 18 Robbins, E.I. ................................................. , ............................................. 53 

Leventhal, J.S ................................................................................................ 9 

Lewis, S.D .................................................................................................... 34 

Lim, Meng Sze Wu .................................................................................... 37 

Lubeck, C.M .................................................................................................. 9 

Lya'ns, P.C ............................................................................................. 29, 44 

Robbins, S.L ........ ~ ............................................................................... 18, 36 

Roberts, S.B ....................................................................................... , ........ 53 

Robinson, Keith ........................................................................... , .............. 54 

Root, D.H ............................................................................................... 1, 31 

Rumpler, Janos ........................................................................................... 33 

Lyons, W.B .................................................................................................. 40 

s 

M 

Macke, D .L ................................................................................................ 29 

Magoon, L.B ........................................................................................... 4, 29 

Marlow, M.S ........................................................................................ 14, 17 

Masson, D .................................................................................................... 14 

Mast, R.F ........................................................................................ 23, 27, 31 

Sanchez, J.D ............................................................................................... 33 

SanFilipo, J.F. , ............................................................................................ 58 

Scanlon, K.M ....................................................................................... 13, 52 

Schenk, C.J ..................................................................................... 24, 38, 55 

Schlee, J.S ............................................................................................ 48, 52 

Schmoker, J.W ............................................................................... 49, 55, 56 

Scholl, D.W .......................................................................................... 17, 56 

Masters, C.D ......................................................................................... 28, 32 Schuenemeyer, J.H .................................................................................... 14 

Mattick, R.E ............................................................................................... 33 Schumann, R.R .......................................................................................... .42 

McCabe, P .1 ................................................................................................. 33 Schweinfurth, S.P ........................................................................................ 58 

McCulloch, D.S ........................................................................................... 34 Sheetz, Linda ............................................................................................. 48 

McGregor, B.A ........................................................................................... 35 Simon, F.0 ................................................................................................... 58 

Mee, J.S ........................................................................................................ 35 Soebakty, A.D ............................................................................................. 37 

Milici, R.C ...................................................................................................... 2 Spencer, C ...................................................................................................... 3 

Milkereit, B .................................................................................................... 3 Spencer, C.W ................................................................................. 23, 27, 58 

Miller, J.J ............................................................................................. 18, 36 Stanley, Dal ................................................................................................. 59 

Molenaar, C.M ....................................................................................... 4, 37 Stanley, R.G ................................................................................................ 22 

Stanton, R.W .................................................................................. 10, 45, 65 

N,O 

Nagy, Iren .................................................................................................... 33 

Neuzil, S.G ................................................................................................... 37 

Stevenson, A.J ............................................................................................. 14 

Stricker, G.D .................................................... , ......................................... 59 

Supardi ..................................................................................................... 8, 37 

Swift, B.A ..................................................................................................... 48 

Nuccio, V.F ................................................................................................ 38 Szanyi, Bela ........................................................................................... 33, 37 

O'Connor, J.T ............................................................................................. 39 

O'Leary, D.W ............................................................................................ 52 

Oman, C.L ............................................................................................ 35, 39 

Orem, W.H ........................................................................................... 40, 42 

Otton, J.K .................................................................................................... 42 

Outerbridge, W.F ................ , ...................................................................... 58 

Owen, D.E ............................................................................................ 42, 62 

T,U 

Taylor, D.J ..................................................................................................... 6 

Tennyson, M.E ............................................................................................ 61 

Thomas, R.E ............................................................................................... 16 

Threlkeld, C.N ........................................... , ................................................ 51 

Turnbull, Peter .............................................................................................. 8 

Turner-Peterson, C.E ................................................................................ 62 

p Tuttle, M.L ................................................................................................. 24 

Palacas, J.G ........................................................................................... 44, 49 Twichell, D.C ................................................................................. 35, 52, 63 

Palmer, C.A .................................................................................. 29, 35, 44 Ujfalusy, Antal ............................................................................................ 33 

Parrish, J.T .................................................................................................. 61 Ulmishek, Gregory .................................................................................... 63 

Parson, L.M .................................................................................. 13, 14, 63 

Pawlewicz, M.J ........................................................................................ 1, 45 V-Z 

Pierce, B.S .................................................................................................. 45 

Pierce, F.W .................................................................................................. 47 

Pitman, J.K ................................................................................................. 48 

Poag, C.W .................................................................................................... 48 

Pollastro, R.M ...................................................................................... 49, 55 

Popenoe, P ................................................................................................. 52 

Powers, R.B ................................................................................................. 31 

Pratt, L.M ................................................................................................... 10 

Valentine, P.C ......................................... , ................................................... 52 

Vallier, T.L ................................................................................................. 14 

Vedder, J.G ........................................................................................... 17, 56 

Verheyen, T.V ........................................................................................... 18 

Vuletich, A.K. ......................................................................... , ................... 51 

Wandrey, C.J ............................................................................................... 27 

Warwick, P.D ................................................................................... , .......... 58 

Weaver, J.N ................................................................................................ 64 

Wilson, M.A ................................................................................................ 18 

R Winget, E.A ............................................................................................... 52 

Revesz, !. ...................................................................................................... 37 Winston, R.B ............................................................................................... 65 

Reynolds, M.W .......................................................................................... 49 Wnuk, Christopher .............................................................................. 37, 58 

Rice, D.D ............................... , ..................................................................... 51 Zielinski, R.A .............................................................................................. 42 

70 

*U.S. GOVERNMENT PRITNJNG OFFICE: 1988-0-573-047/66022