Geochemistry of Two Interbeds in the 

Pennsylvanian Paradox Formation, 

Utah and Colorado A Record of Deposition and 

Diagenesis of Repetitive Cycles in a Marine Basin

U.S. GEOLOGICAL SURVEY BULLETIN 2000-N
Cover. View south toward the La Sal Mountains along the Colorado River between Cisco 

and Moab, Utah. Fisher Towers in center is composed of Permian Cutler Formation and 

capped by Triassic Moenkopi Formation. The prominent meas at left center is capped by 

Jurassic Kayenta Formation and Wingate Sandstone and underlain by slope-forming Triassic Chinle and Moenkopi Formations. The Chinle-Moenkopi contact is marked by a thin, 

white, ledge-forming gritstone. The valley between Fisher Towers and Fisher Mesa in the 

background is part of Richardson Mesa, part of Professor Valley. Photograph by Omer B. 

Raup.
Geochemistry of Two Interbeds in the 

Pennsylvanian Paradox Formation, 

Utah and Colorado A Record of Deposition and 

Diagenesis of Repetitive Cycles in a Marine Basin

By Michele L. Tuttle, Timothy R. Klett, 

Mark Richardson, and George N. Breit

EVOLUTION OF SEDIMENTARY BASINS PARADOX BASIN 

A.C. Huffman, Jr., Project Coordinator

U.S. GEOLOGICAL SURVEY BULLETIN 2000-N

A multidisciplinary approach to research studies of 

sedimentary rocks and their constituents and the 

evolution of sedimentary basins, both ancient and modern

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1996
U.S. DEPARTMENT OF THE INTERIOR 

BRUCE BABBITT, Secretary

U.S. GEOLOGICAL SURVEY 

Gordon P. Eaton, Director

For sale by U.S. Geological Survey, Information Services

Box 25286, Federal Center

Denver, CO 80225

Any use of trade, product, or firm names in this publication is for descriptive purposes only and 

does not imply endorsement by the U.S. Government

Library of Congress Cataloging-in-Publication Data

Geochemistry of two interbeds in the Pennsylvanian Paradox Formation, Utah and 

Colorado : a record of deposition and diagenesis of repetitive cycles in a marine 

basin / by Michele L. Tuttle ... [et al.].

p. cm. (Evolution of sedimentary basins Paradox Basin ; N) 

(U.S. Geological Survey bulletin ; 2000)

Includes bibliographical references.

Supt.ofDocs.no.: 119.3: 2000-N

1. Geochemistry Utah. 2. Geochemistry Colorado. 3. Sedimentation and 

deposition Utah. 4. Sedimentation and deposition Colorado. 5. Diagenesis 

Utah. 6. Diagenesis Colorado. 7. Geology, Stratigraphic Pennsylvanian. 

8. Paradox Formation. I. Tuttle, M. L. II. Series. III. Series: Evolution of 

sedimentary basins Paradox Basin ; ch. N. 

QE75.B9 no. 2000-N 

[QE515] 

557.3 s dc20

[551.9792] 96-5830

CIP
CONTENTS

Abstract .......................................................................................................................... Nl

Introduction .................................................................................................................... 1

Middle Pennsylvanian Paradox Formation .................................................................... 3

Methods........................................................................................................................... 4

Sampling Methods ................................................................................................. 4

Analytical Methods ................................................................................................ 5

Results and Discussion ................................................................................................... 8

Presentation of Data ............................................................................................... 8

Lithofacies and Sedimentation ............................................................................... 9

Lithologic Classification ................................................................................ 9

Mineralogy...................................................................................................... 10

Clastic Sedimentation .................................................................................... 13

Authigenic Mineral Precipitation ................................................................... 13

Organic Geochemistry ........................................................................................... 15

Organic-Matter Data ...................................................................................... 15

Productivity, Preservation, and Maturation of Organic Matter ...................... 15

Trace-Metal Geochemistry ..................................................................................... 18

Trace-Metal Data ........................................................................................... 18

Trace-Metal Enrichment ................................................................................ 18

Sulfur and Iron Geochemistry ................................................................................ 21

Sulfur Phases and Their Isotopic Composition .............................................. 21

Iron and Its Degree of Pyritization ................................................................. 21

Pyrite Formation ............................................................................................ 21

Variability Within a Basin-Center Core ......................................................................... 24

Geochemical Processes During Deposition and Diagenesis of Shales

of the Paradox Formation ........................................................................................... 24

Conclusions .................................................................................................................... 29

References Cited ............................................................................................................ 29

Appendix 1 Core Descriptions and Sampling Information ......................................... 33

Appendix 2 Lithologic, Chemical, Isotopic, and Mineralogic Data

for Core Samples in Study ......................................................................................... 53

FIGURES

1. Map showing location of core holes and outcrops used in study, and transects A-A' and B-B',

Paradox Basin .............................................................................................................................................................. N2

2. North-south cross section of the Pennsylvanian Paradox Formation, Paradox Basin................................................. 3

3. Diagram showing generalized rock types in idealized cycles..................................................................................... 4

4. Map showing distribution of environments during deposition of cycles 5 and 3 of the

Pennsylvanian Paradox Formation............................................................................................................................... 5

5. Isopach maps of interbeds in cycles 5 and 3 of the Pennsylvanian Paradox Formation............................................. 6

6. Schematic diagram of analytical scheme to separate forms of sulfur......................................................................... 9

7. Crossplot of total clay versus carbonate carbon.......................................................................................................... 12

8. Maps of means of minerals in individual cycles and cores......................................................................................... 14

9. Maps of means of selected chemical parameters in individual cycles and cores........................................................ 16

10. Crossplots of chromium and nickel versus aluminum ................................................................................................ 19

III
IV CONTENTS

11. Crossplots of enriched chromium and enriched nickel versus organic carbon........................................................... 20

12. Photomicrographs of pyrite morphologies.................................................................................................................. 22

13. Crossplot of disulfide versus reactive iron.................................................................................................................. 23

14. Crossplot of 534Soi versus degree of pyritization for samples from cycle 5 .............................................................. 23

15. Depth profiles of selected chemical parameters in cycle 3, Shafer core..................................................................... 25

16. Schematic diagram showing conditions during deposition of shales of groups 1 and 2............................................. 28

	TABLES

1. Sampling information, Pennsylvanian Paradox Formation......................................................................................... N7

2. Number of samples of each rock type sampled in cycles 3 and 5............................................................................... 8

3. Characteristic peaks measured on X-ray diffractograms ............................................................................................ 8

4. Trace elements that were censored and their detection limits..................................................................................... 9

5. Arithmetic means of characteristic X-ray diffraction peak heights ............................................................................ 10

6. Means of selected chemical parameters and sulfur isotopic compositions................................................................. 11

7. Means of trace metals in shales, Pennsylvanian Paradox Formation.......................................................................... 18
GEOCHEMISTRY OF TWO INTERBEDS IN THE

PENNSYLVANIAN PARADOX FORMATION,

UTAH AND COLORADO A RECORD OF DEPOSITION

AND DIAGENESIS OF REPETITIVE CYCLES IN A

MARINE BASIN

By Michele L. Tuttle, 1 Timothy R. Klett, 1 Mark Richardson,2 and George N. Breit 1

ABSTRACT

During the Pennsylvanian Period, repetitive cycles of 

marine evaporite, carbonate, and siliciclastic rocks were 

deposited in the Paradox Basin of Utah and Colorado. The 

carbonate (dolostone and limestone) and siliciclastic (siltstone and shale) rocks comprise interbeds bounded above 

and below by anhydrite and halite. The interbeds host petroleum source rocks, and shallow-marine carbonate rocks 

within the interbeds on the southwestern platform of the 

basin are reservoirs for generated hydrocarbons. The variability in the geochemistry of sulfur, carbon, and metals in 

the shale, carbonate rocks, siltstone, and anhydrite is related 

to areal and temporal changes in processes related to a distinct set of conditions that controlled the source of the 

organic matter and clastic material, seawater circulation, 

sedimentation rate, and water-column/sediment redox conditions.

At the onset of transgression, circulation was good in 

the upper part of the water column, but a bottom brine was 

present in the deeper parts of the basin due to dissolution of 

evaporite minerals. Primary productivity in the upper part of 

the water column was not high, and a large part of the 

organic matter in the sediment was terrestrial in origin. The 

anoxic nature of the brine promoted sulfide mineral formation at the sediment-water interface and retention in the sediment of metals such as chromium and nickel. Plagioclase 

was diagenetically altered to potassium feldspar as a result of 

high potassium content in the brine. As transgression proceeded, the water column mixed, diluting the brine and

.S. Geological Survey, Box 25046, Mail Stop 916, Denver Federal 

Center, Denver, Colorado 80225.

2Exxon Production Research Company, P.O. Box 2189, S-169, Houston, Texas 77252-2189.

partially oxygenating the bottom water. Productivity 

increased, and reworking of organic matter at the sediment-water interface released phosphorous, now available 

for apatite formation, and some of the adsorbed metals. The 

redox front moved into the sediment where sulfide minerals 

formed. The best petroleum source rocks were deposited 

during this later phase.

INTRODUCTION

The Middle Pennsylvanian Paradox Formation of the 

Hermosa Group in southeastern Utah and southwestern Colorado (fig. 1) comprises repetitive sequences, each composed of evaporite, carbonate, and siliciclastic units; these 

sequences are referred to hereafter as cycles (Kite, 1970). 

The areal and vertical distribution of rock types within these 

cycles (figs. 2 and 3) reflects the interaction of eustasy, tectonics, and local climate. Interbeds of carbonate and shale 

with minor siltstone and sandstone are bounded above and 

below by anhydrite and halite. Many of the shale units of the 

interbeds are petroleum source rocks that can be stratigraphically correlated throughout the basin (fig. 3) and, in the past, 

have been interpreted as time-correlative units (Kite and 

Buckner, 1981). Production of hydrocarbons generated 

from these shales exceeds 54 million metric tons of oil and 

28 billion m3 of gas (Baars and Stevenson, 1982).

In this report, we present chemical, sulfur isotopic, and 

mineralogical data for 159 samples for 13 cores from laterally persistent interbeds within two cycles in the upper part 

of the Paradox Formation cycle 3, in the Ismay oil-producing interval, and cycle 5, in the Desert Creek oil-producing 

interval. Oil-producing intervals are described in Kite and 

Buckner (1981). Lateral and vertical changes in geochemistry of the interbeds within and between the two cycles are

Nl
N2 EVOLUTION OF SEDIMENTARY BASINS PARADOX BASIN

-111 -110C -109° -108C

39 C

38 C

37 C

36°

Colorado River -

./'

/ 

GrancUJ unction

Gunnison River /

Uncompahgre \ 

River

FARTHEST EXTENT 

OF HALITE I

Animas 

'River

Durango 

O|.ORApO

NEV\|MEXIQO

Farmington-/A/av^° 

 % Reservoir

o___25 

KILOMETERS

Figure 1. Location of core holes and outcrops (solid circles) used in study, and transects A-A' and B-B', Paradox Basin. Sampling information is given in table 1. Heavy line delineates boundary of Paradox Basin as defined by approximate limit of the halite facies in the 

Pennsylvanian Paradox Formation. Sh, Shafer No. 1; G, Gibson Dome No. 1; C, Crowley Ranch No. 1; D, Duncan Tevault No. 1; N, 

Norton-Federal No. 1-4; W, Woods Unit No. 1-S; U, Ute Mountain No. 44-34; L, Lake Canyon Prospect Federal No. 1-27; P, Pickett 

Federal No. 1-33; A, Aztec Federal No. 1; WW, West Water Creek No. 1;S, State No. 1-16; E, Elk Ridge No. 1; H, Honaker Trail outcrop. 

Modified from Raup and Hite (1992).
GEOCHEMISTRY OF TWO INTERBEDS, PENNSYLVANIAN PARADOX FORMATION, UTAH AND COLORADO N3

North

170km

South

p 33

Figure 2. North-south cross section in the Paradox Basin of the 

Pennsylvanian Paradox Formation showing the extent of halite 

(dark shading) and carbonate (light shading) units. Selected cycles 

are numbered. Modified from Hite (1970).

used to identify geochemical processes during formation of 

the interbeds. A comparison of these processes with the 

detailed geochemical variability within a basin-center core 

helps to place the processes into a stratigraphic framework. 

The results of these two exercises are used to infer conditions 

of deposition and diagenesis of the shales within the interbeds to help understand formation of the source rocks of the 

Paradox Formation.

Acknowledgments. EXXON Production Research 

provided the organic pyrolysis analyses, and Robert Rye of 

the U.S. Geological Survey (USGS) provided access to his 

isotope laboratory. Paradox Basin researchers of the USGS 

and outside organizations are acknowledged for sharing their 

observations and insights regarding the stratigraphy and 

geochemistry of the evaporites and their interbeds. This 

report has greatly benefited from the constructive reviews of 

Joseph Hatch and Robert Zielinski. The work on which this 

report is based was funded by the U.S. Geological Survey 

Evolution of Sedimentary Basins Program.

MIDDLE PENNSYLVANIAN PARADOX 

FORMATION

The Paradox Basin is a northwest-trending structural 

depression that formed as a result of continent-continent collisions along the southern and southeastern margins of North 

America (Huffman and Condon, 1993). During the Middle 

Pennsylvanian, alternation of seawater incursions into the 

basin and periods of evaporitic conditions resulted in deposition of 33 evaporite-carbonate-siliciclastic cycles (Hite, 

1960; Hite and Buckner, 1981; Huffman and Condon, 1993; 

Williams-Stroud, 1994). Circulation into the basin from the

open ocean was restricted by surrounding uplifts (Peterson 

and Hite, 1969; Mallory, 1975) and by the large Four Corners carbonate platform to the south. The dominant ocean 

accessways were the Cabezon seaway to the southeast 

(Wengerd, 1962) and a seaway between the Emery and 

Uncompahgre uplifts to the north (Szabo and Wengerd, 

1975); minor accessways may have been present to the west. 

Circulation through these seaways was controlled by tectonics and (or) eustasy (Huffman and Condon, 1993).

During periods when ocean circulation was shut off, 

beds of evaporites formed, first anhydrite, then halite, and 

finally sylvite and carnallite. These minerals previously 

were thought to have formed through the evaporation of seawater; however, recent work shows that chemical paragenesis of the Paradox Formation evaporites is inconsistent with 

a simple seawater origin and may reflect a large meteoric 

water contribution during evaporitic periods (see 

Williams-Stroud, 1994, for discussion of the origin of the 

Paradox Formation evaporites).

For any one Paradox Formation cycle, the extent of 

rock types in the cycle varies from basin center to basin margin (fig. 3). In the deeper parts of the basin, halite (plus or 

minus potash salts) is present and is the most saline mineral 

assemblage observed (Hite, 1983). Removal of halite by dissolution has occurred intermittently throughout the basin 

(Hite and Buckner, 1981; Kendall, 1987) and, in part, may be 

responsible for the present-day distribution of halite. In this 

report, as in many others, the farthest extent of preserved 

bedded halite (fig. 2) (salt cycle 6 of Hite, 1961) is used to 

define the extent of the Paradox Basin (fig. I). The areal distribution of anhydrite in any given cycle extends past the 

boundary of the halite but, for the two cycles studied, is 

within the cycle-6 halite boundary (fig. 1). Carbonate-siliciclastic interbeds between the halite and anhydrite comprise 

siltstone; dolostone; limestone; and argillaceous, dolomitic, 

and calcareous shale. Near the basin margins, no evaporites 

were deposited, and the sequence is dominantly a limestone 

succession with argillaceous and calcareous shale. The 

basin margin was a carbonate shelf that was exposed 

subaerially and eroded to varying degrees during evaporite 

deposition within the deeper parts of the basin. Arkose in the 

northern end of the basin formed from siliciclastic detritus 

shed off the ancestral Uncompahgre highland.

The areal distribution of arkose, halite, anhydrite, and 

carbonate in cycles 3 and 5 as shown in figure 4 is based on 

core data (Reid and Berghorn, 1981). The maps of figure 4 

show the extent of lithofacies preserved from the regressive 

part of the cycle. The preserved halite facies of cycle 5 (fig. 

4A) is less areally extensive than the maximum extent of preserved halite in the basin (heavy line, fig. 4). The anhydrite 

facies of cycle 5 is present throughout most of the basin. The 

areal extent of the halite and anhydrite facies of cycle 3 (fig. 

45) is much smaller than that of cycle 5.
N4 EVOLUTION OF SEDIMENTARY BASINS PARADOX BASIN

Shelf

CD 

_Q

CD 4 

c

LimestoneCD 

_Q

CD -i 

C

Margin Center

CD 

.Q

Anhydrite

v/y//

Halite

Anhydrite

Dolostone

Shale 

Dolostone

Anhydrite

I Y Y Y Y Y Yl

EXPLANATION

High stand (maximum flooding surface) 

Removed by erosion

Figure 3. Generalized rock types in idealized cycles from the basin center, basin margins, and shelf. Dolo, dolostone.

The thickness of the interbeds of cycles 3 and 5 vary as 

shown in the isopach maps of figure 5. The interbed of cycle 

5 (fig. 5A) thickens to 9 m (30-ft contour) in the southwestern 

part of the basin, and slightly thicker areas (as thick as 12m, 

40-ft contour) of small extent are present in the eastern part 

of the basin. The interbed of cycle 3 (fig. 5B) is generally 

much thicker (as thick as 61 m, 200-ft contour) than that of 

cycle 5 and is thickest near the Uncompahgre highland.

METHODS

SAMPLING METHODS

We collected 151 samples from interbeds of cycles 3 

and 5 in 13 cores and 1 sample from an outcrop location that 

represents the southwesternmost part of the Paradox Formation accessible for sampling. Seven anhydrite samples from 

above and below the interbeds were collected in cores containing the evaporite facies. Well locations, API numbers, 

sampled intervals, and number of samples collected are summarized in table 1, and well locations are shown in figures 1,

4, and 5. All of the wells are within the boundary of the basin 

as defined by the farthest extent of halite (fig. 1). The wells 

are distributed along two intersecting transects that form a 

sideways "T" within the basin (fig. 1). The transects for each 

cycle are slightly different (compare figs. 4A and 4B); however, areal coverage for each cycle is believed to characterize the nature of basinwide variation in measured 

geochemical parameters. The southwest-to-northeast 

transect (A-Af, fig. 1) is perpendicular to the Uncompahgre 

trough (a structural depression along the northeastern margin of the basin that parallels the ancestral Uncompahgre 

uplift) (Hite, 1968). This transect extends from the carbonate shelf, across the anhydrite facies, to the halite facies near 

the trough (fig. 4). The northwest-to-southeast transect 

(B-B', fig. 1) parallels the trough and extends from the halite 

facies, across the anhydrite facies, to the shelf (fig. 4). 

Samples in the latter transect were not collected from within 

or northeast of the trough because sequences have been 

severely disrupted by salt diapirism.

Gamma-ray logs, lithofacies descriptions, and sample 

distribution within the 13 sampled core intervals are presented in Appendix 1. Sampling density was based on the 

thickness of the interbed in the core and on the thickness and
GEOCHEMISTRY OF TWO INTERBEDS, PENNSYLVANIAN PARADOX FORMATION, UTAH AND COLORADO N5

EXPLANATION

Arkosic facies 

Halite facies 

Anhydrite facies 

___ Carbonate (shelf) facies

Figure 4. Distribution of environments during deposition of cycles 5 and 3 of the Pennsylvanian Paradox Formation. Abbreviations of 

core (solid circles) names are given in table 1. Heavy line delineates boundary of Paradox Basin as defined by approximate limit of the halite 

facies in the Pennsylvanian Paradox Formation. Modified from Reid and Berghorn (1981). A. cycle 5. B, cycle 3.

heterogeneity of each lithologic unit as identified in the core 

description. In some cases, the entire interbed was not available for sampling. The extent of interbed coverage by the 

core was determined by comparing the sampled interval with 

gamma-ray logs and, if available, with the location of 

evaporite beds in the core (see Appendix 1). The number of 

samples represented by each rock type in cycles 3 and 5 is 

given in table 2; rock types in this table were redefined from 

those in the core descriptions using mineralogical and chemical data as presented in the beginning of the Results and Discussion section of this report.

Each sample was cut to about 5 cm long and then split 

lengthwise with a diamond saw cooled with tap water. After 

cutting, the excess water on the samples was removed 

promptly by blotting with paper towels, and the samples 

were air dried at room temperature (25°C). Two splits, one

approximately 2 g and one approximately 5 g, were reserved 

for polished thin section preparation and Rock-Eval pyrolysis, respectively. The remaining sample (as much as 50 g) 

was crushed by mortar and pestle and then ground in a 

ceramic ball mill to a <125-|J.m powder.

ANALYTICAL METHODS

Epoxy-impregnated, polished thin sections were 

commercially prepared for representative intervals in each 

core and examined under both transmitted and reflected light 

to determine sulfide-mineral morphology. Packed-powder 

mounts were analyzed for whole-rock mineralogy by X-ray 

diffractometry using nickel-filtered, copper K-alpha radiation. Diffractograms were from 4° to 64° two-theta.
N6 EVOLUTION OF SEDIMENTARY BASINS PARADOX BASIN

120

40

H

0 25 KILOMETERS

Figure 5. Isopach maps (in feet) of interbeds in cycles 5 and 3 of the Pennsylvanian Paradox Formation. Abbreviations of core (solid 

circles) names are listed in table 1. Approximate limit of halite facies in the Pennsylvanian Paradox Formation is shown as in figure 4. 

A, cycle 5. B, cycle 3.

Relative mineral contents were determined using relative 

intensities (units of 0.1 inch) of a selected diffraction peak 

chosen to represent each mineral. The values of degrees 

two-theta for the characteristic peaks of each mineral are 

listed in table 3.

Total carbon and organic carbon (Cofg) were measured 

on a commercial apparatus using an induction furnace and a 

thermal conductivity cell (reproducibility ±10 percent). The 

carbon measured on samples treated with 6 MHC1 is assumed 

to be organic carbon. Carbonate carbon ( 033) is the calculated difference between organic carbon and total carbon.

The type of organic matter (terrestrial or algal), as well 

as the maturity of the organic matter, is related to results 

from Rock-Eval pyrolysis. Rock-Eval analyses were performed by Exxon Production Research Company in Houston, Texas. Rock-Eval pyrolysis measures the amount of 

hydrocarbons (HC) and CO2 generated from the sample as a 

function of temperature (Tissot and Welte, 1984). The characteristic Sj and S2 peak areas relate to milligrams of HC 

generated per gram of rock over specific temperature ranges, 

and the 83 peak relates to the amount of CO2 (in milligrams) 

generated per gram of rock. These values convert to hydrogen and oxygen indices (HI and OI) as follows:

HI = S2 mg HC/g C0rg, and

OI=S3 mgC03/gCorg

The Tmax value is the temperature at which the S2 peak intensity is greatest and is commonly used to assess the thermal 

maturity of organic matter in source rocks.

Total sulfur content was determined by two methods: 

(1) a commercial apparatus using an induction furnace and 

an infrared detection system (reproducibility ±10 percent), 

and (2) the summation of sulfur-species concentrations 

obtained by chemical separation (fig. 6). Details of the sulfur species separation technique and its development are 

described in Tuttle and others (1986). In this technique, a 

powdered sample is reacted with hot 6 M HC1, then with hot, 

acidified 1 M Cr2+ solution to sequentially extract acid-volatile sulfide, disulfide, and sulfate species. The residue is 

fused with an Eschka mixture to extract organically bound 

sulfur. Acid-volatile and disulfide sulfur are recovered as 

silver sulfide. Sulfate and organically bound sulfur are precipitated as barium sulfate. The precipitates are weighed and 

the weight percent of each sulfur species in the original sample calculated. Results were reproducible to within ±10 percent except near the detection limit (0.01 weight percent) 

where reproducibility approached ±20 percent.

The precipitates from the separation procedure (silver 

sulfide and barium sulfate) are converted to SO2 in a vacuum 

line by combusting with vanadium oxide or elemental copper, respectively. Both combustions take place in the
Table 1. Sampling information, Pennsylvanian Paradox Formation, Utah and Colorado.

[Abbreviations for well names shown in parentheses are as shown in figure 1. Locations are listed in the order: Township, Range, and section]

Well name

91 PCH 1 HT

Honaker Trail outcrop (H)

U.S. Department of Energy

Elk Ridge No. 1 (E)

Carbonit Exploration Inc.

State No. 1-16 (S)

Southland Royalty Co.

West Water Creek No. 1 (WW)

E.L. and B.R. Cox

Aztec Federal No. 1 (A)

McCulloch Oil and Gas Corp.

Pickett Federal No. 1-33 (P)

Santa Fe Energy Co.

Lake Canyon Prospect Federal No. 1-27

Davis Oil Company

Duncan Te vault No. 1 (D)

Delhi-Taylor Oil Company

ShaferNo. 1 (Sh)

U.S. Department of Energy

Gibson Dome No. 1 (G)

Transco Exploration

TXPOC Crowley Ranch No. 1-25 (C)

McCulloch Oil and Gas Corp.

Norton Federal No 1 -4 (N)

Celsius Energy

Woods Unit No. 1-S (W)

Houston Oil and Mineral Corp.

Ute Mountain No. 44-34 (U)

'Kite (1970).

2Depths from well logs.

Location

41S-18E-SW29

San Juan Co., Utah

37S-19E-30

San Juan Co., Utah

39S-21E-SENW16

San Juan Co., Utah

38S-22E-SWSE4

San Juan Co., Utah

37S-23E-24

San Juan Co., Utah

36S-25E-NESW33

San Juan Co., Utah

36S-25E-NWNW27

(L) San Juan Co., Utah

40N-20W-SWSE35

Dolores Co., Colorado

27S-20E-15

San Juan Co., Utah

30S-21E-21

San Juan Co. , Utah

34S-25E-25

San Juan Co. , Utah

38N-18W-SENE4

Montzuma Co., Colorado

37N-18W-SENW20

Montzuma Co., Colorado

34N-14W-SESE34

Montzuma Co., Colorado

API number

~

4303790625

4303730603

4303730713

4303730724

4303730539

4303730692

503306047

Not known

4303796006

4303730978

508306260

508306359

508306172

Cycle 1

5

3

5

3

5

3

5

5

3

5

3

5

3

5

5

3

5

5

3

Shale interval

Top (m)

774

815

1,689

1,738

1,922

1,945

1,721 2

1,750

1,940

773 2

8762

871 2

9342

1,800

1,804

1,851

1,802

2,650

Bottom (m)

789

824

1,709

1,7532

1,937

1,953

1,727

1,758

1,945

783 2

8992

8842

1,804

1,824

1,853

1,805

2,6872

Cored i

Top (m)

Outcrop

7773

7973

1,682

1,735

1,921

1,943

1,720

1,751

1,940

765 3

8753

8683

9343

1,798

1,804

1,842

1,802

2,649

2,656

3Entire well was cored. Depth refers to sampled intervals.
N8 EVOLUTION OF SEDIMENTARY BASINS PARADOX BASIN

Table 2. Number of samples of each rock type sampled in cycles 

3 and 5, Pennsylvanian Paradox Formation, Utah and Colorado.

Rock type

Anhydrite 

Dolostone

Limestone

Siltstone

Dolomitic shale

Calcareous shale

Argillaceous shale

Total

7 

22

19

14

11

51

35

Cycle 3

3 

11

10

3

8

33

18

Cycle 5

4 

11

9

11

3

18

17

Table 3. Characteristic peaks measured on X-ray diffractograms.

[Alternative peaks were used when interference was present for primary 29 peak; 

alternative peak units were adjusted to those for 29 peak using intensity factors]

Mineralogy

Gypsum 

Clay 

Quartz 

Anhydrite

Potassium feldspar 

Sodium feldspar 

Calcite

Dolomite

Halite

Fluorapatite 

Pyrite

 Degrees 26

11.70 

19.45-19.89 

20.83

25.5

27.51 

27.77-27.89 

29.40

30.96

31.69

31.93 

33.04

Alternative peaks x 

intensity factors

31. 37x2.86 or 

38.64 x 5.00

43.14x5.56

41.15x 3. 33 or

37.36 x 10.00

56.48 x 1.43

presence of quartz glass to equilibrate the oxygen isotopic 

composition of the SCK Isotopic analysis of the SCb was 

performed using a high-resolution, 6-inch, 60°-sector mass 

spectrometer. All isotope results are reported in 834S 

notation3 relative to the Canon Diablo troilite standard 

(CDT). 834S values were reproducible to within ±0. l%o.

An aliquot of 6 M HC1 filtrate from the speciation procedure was collected and analyzed by atomic absorption 

spectrophotometry for iron (reproducibility ±10 percent). 

The HCl-soluble iron was used to calculate reactive iron 

(Ferct) concentrations. Ferct is operationally defined as iron 

that is available for sulfidization by reduced sulfur species 

(Berner, 1984) and is calculated as

Ferct = FeHCi + FeDl 

where

FeRCl is HCl-extractable iron (iron in carbonate, oxide,

acid-volatile sulfide, and possibly clay mineral

phases), and

3634SX = [<Rx-RcDT>/RcDT] * o, where R is 34S/32S.

is the iron in disulfide minerals and is calculated 

using the sulfur speciation value for disulfide and 

assuming stoichiometric FeS2-

Berner (1970) defined degree of pyritization of the 

reactive iron (DOPr) as the measure of the fraction of reactive iron available for sulfidization to form pyrite. Degree of 

pyritization traditionally has been used to examine iron and 

sulfur limitation on pyrite formation during sediment 

diagenesis. Recently, Canfield and others (1992) showed 

that DOPr values are a crude measure of the amount of iron 

potentially reactive and that their use for determining controls on pyrite formation is limited. DOPr is calculated as

DOPr = FeDi/Ferct

and, in this report, will be used according to Canfield's definition.

Inductively coupled plasma-atomic emission spectrometry (ICP-AES) (Briggs, 1990) was used to determine 

major, minor, and trace elements in core samples. Estimated 

precision for most reported elements is ±10 percent (relative 

standard deviation). Other trace elements sought, but consistently below their detection limits, are listed in table 4.

Arsenic and selenium were determined for 27 selected 

shale samples using continuous-flow hydride-generation 

atomic absorption spectrophotometry (HG-AAS) (Crock 

and Sanzolone, 1990). The method has a reproducibility of 

better than ±10 percent.

RESULTS AND DISCUSSION

PRESENTATION OF DATA

Qualitative petrographic data are summarized in 

Appendix 1, and chemical, isotopic, and calculated data 

(Ferct and DOPr) are tabulated in Appendix 2. Although all 

chemical data are included in Appendix 2, not all results are 

discussed in this report. Means for the various rock types 

and means for core that include all rock types except anhydrite were calculated using whole-rock data. In this report, 

means and deviations are either arithmetic or geometric, 

depending on the statistical distribution of the data (tables 5 

and 6).

Within any one core, an interbed generally includes 

several rock types that reflect temporal facies changes. The 

means for a given cycle in each core were calculated to 

investigate compositional variations in the interbeds across 

the basin. These variations can then be related to geochemical processes. Comparison of means to examine these processes on a basinwide scale is restricted to those cores that 

completely penetrate the interbed and for which samples 

represent the lithologic distribution within the core. Cores 

that meet these criteria are shown in bold in tables 5 and 6 

and are shown by the solid part of location dots in subsequent maps of geochemical means. Means for cores that do 

not meet the criteria (shown as open circles in figures) are
GEOCHEMISTRY OF TWO INTERBEDS, PENNSYLVANIAN PARADOX FORMATION, UTAH AND COLORADO N9

Filtrant Filtrant

acid volatile sulfate

0

°disulfide

4(s)

'organic

Figure 6. Analytical scheme to separate forms of sulfur contained in rock samples from the Paradox Formation. See text for 

explanation.

Table 4. Trace elements that were censored (concentrations 

below detection limits) and their detection limits.

Trace element

Au. ......................

Bi.. .....................

Cd.. .....................

Eu.. .....................

Ho.......................

Sn... ....................

Ta... ....................

Th........... ............

U.. ......................

Yb.... ...................

Detection limit (ppm)

............................8

............................10

.............................2

............................2

............................4

............................5

...........................40

............................4

.......................... 100

............................ 1

presented on the maps for comparison but are considered 

less reliable.

LITHOFACIES AND SEDIMENTATION

LITHOLOGIC CLASSIFICATION

A crossplot of the relative amount of clay versus concentration of carbonate carbon (C) was used to define

fields for classifying samples with respect to their rock type 

(fig. 7). The field for shale is defined as having an X-ray 

diffraction (XRD) relative peak height for clay >5 chart 

units (0.5 inches) and CCQS concentrations <3 weight percent. These samples are commonly fissile and fissile bedded. Samples having clay peak heights >5 chart units and 

with Ccc>3 concentrations between 3 weight percent (25 

percent calcite equivalence) and 6 weight percent (25-50 

percent calcite equivalence) are classified as calcareous or 

dolomitic shale. Calcareous and dolomitic shales are 

defined by the predominance of calcite or dolomite in the 

sample as determined by X-ray diffraction and transmitted-light petrography. If dolomite is greater than calcite, 

the upper limit for Ccc>3 concentrations is increased to 6.5 

weight percent (50 percent dolomite equivalence). Calcareous samples that have clay intensities >5 chart units and 

CCQ? concentrations >6 weight percent are classified as 

shaly to silty limestone, and dolomitic samples with >6.5 

weight percent CCOB are classified as shaly to silty dolostone. Samples with clay intensities <5 chart units and Ccc>3 

concentrations >6 weight percent are classified either as 

limestone or dolostone, depending on the dominant carbonate mineral. The remaining samples were classified as
N10 EVOLUTION OF SEDIMENTARY BASINS PARADOX BASIN

Table 5. Arithmetic means of characteristic X-ray diffraction peak heights by rock type and by core and cycle, Pennsylvanian Paradox 

Formation, Utah and Colorado.

[Units shown are 0.1-inch units; standard deviations are in parentheses. Bold type represents sampled cycle intervals that are representative of the entire interbed. n, number of 

samples]

Rock

type

Dolostone

Limestone

Siltstone

Argillaceous sh.

Dolomitic sh.

Calcareous sh.

All rock types

Core

(cycle)

Shafer (3)

Shafer (5)

Gib son Dome (3)

Gibson Dome (5)

CrowleyRanch(5)

Duncan Tevault (5)

Norton Federal (3)

Norton Federal (5)

Woods (5)

Ute Mountain (3)

Lake Canyon (3)

Pickett Federal (5)

Aztec Federal (5)

West Water Ck. (3)

State(3)

State (5)

Elk Ridge (3)

Elk Ridge (5)

Honaker Trail3 (5)

n

22

19

14

35

11

51

152

n

29

4

15

7

2

4

4

10

8

9

9

14

6

4

6

6

7

7

1

Quartz

22(17)

19(8)

51(13)

28(10)

26(8)

26(7)

27(13)

Quartz

23(9)

34 (22)

27(14)

40 (20)

21

42 (27)

24(3)

28(21)

21 (12)

33(7)

20(3)

30(11)

23(5)

33(4)

33 (23)

25(6)

25(4)

28(12)

24

Clay

4(3)

4(3)

6(4)

12(4)

10(2)

10(2)

9(4)

Clay

feldspar

9(4)

6(4)

9(5)

5(3)

9

9(7)

8(1)

7(4)

9(6)

8(1)

10(4)

13(4)

10(6)

9(3)

4(3)

7(5)

8(2)

10(6)

11

Potassium

feldspar

6(6)

3(4)

26(10)

14(10)

9(5)

6(5)

10(9)

Potassium

feldspar

13(6)

22(15)

6(6)

21 (17)

14

7(5)

1(3)

18(14)

10(6)

1(2)

2(3)

15(9)

8(4)

4(5)

3(4)

0

8(4)

6(7)

10

Sodium

feldspar

5(6)

6(4)

6(9)

10(10)

7(5)

9(5)

8(7)

Sodium

7(5)

0

14(5)

0

0

0

2(2)

5(14)

8(6)

7(2)

13(5)

5(5)

10(3)

7(2)

Calcite

5(7)

170 (59)

54 (42)

51 (27)

22 (32)

110(24)

78 (60)

Calcite

30 (29)

Dolomite

210(71)

68 (34)

87 (44)

30 (23)

130(54)

34(16)

74(73)

Dolomite

90 (78)

6(11)116(128)

90 (48)

20 (24)

95

31 (41)

137(10)

77 (80)

148 (64)

40

94(101)

53(15)

13(21)158(121)

143 (63)

123 (42)

125 (30)

92 (32)

102 (24)

95 (28)

5(4)168(118)

10(3)

7(2)

20(7)

0

90 (43)

103 (47)

68 (34)

100

45 (32)

46(9)

43 (29)

45 (35)

51 (45)

47(12)

34 (20)

69 (56)

70(61)

49 (80)

41

Apatite

<1

<1

<1

3(6)

2(3)

3(2)

2(4)

Apatite

1(3)

10(14)

3(2)

0

0

1(3)

2(2)

1(3)

1(3)

2(1)

3(3)

4(4)

3(4)

4(1)

1(0

2(3)

3(2)

3(3)

4

Pyrite

4(3)

4(3)

5(3)

10(4)

6(3)

9(3)

7(4)

Pyrite

7(4)

7(4)

8(3)

2(1)

9

7(2)

6(1)

5(3)

7(4)

5(2)

9(2)

10(3)

8(5)

10(3)

3(3)

9(6)

9(2)

11(5)

10

Anhydrite 1

15(27)

9(8)

9(21)

4(5)

4(5)

3(3)

6(13)

Anhydrite

2(3)

7(9)

2(6)

1 1 (27)

0

27 (47)

4(1)

16 (20)

8(12)

3(1)

6(3)

6(4)

2(3)

4(1)

1(2)

3(2)

0

11(29)

5

Halite2

4(7)

0

23 (37)

10(21)

5(8)

0

6(17)

Halite2

11(8)

32 (47)

0

58 (40)

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

Occurs as vein filling.

2Occurs as vein filling and also possible contamination during coring.

3Outcrop sample.

siltstone or sandstone, based on thin-section observation, 

quartz peak height, and hand-specimen examination. Samples composed mainly of halite and anhydrite were classified at the time of sampling, and the classification was 

verified using X-ray diffraction data. The total clay-carbonate carbon crossplot (fig. 7) shows the distribution of sample 

types. Shaly to silty limestone is combined with limestone 

and simply referred to as limestone hereafter. Similarly, 

shaly to silty dolomite is classified as dolostone. The rationale for combining these four rock types into two is based on 

the similar chemical characteristics of the two limestone and 

the two dolostone types.

MINERALOGY

A brief narrative of the mineralogy of cored intervals is 

given in the core summaries of Appendix 1. Mean peak 

heights of minerals (table 5) are useful for relative

comparisons among rock types and among many of the 

cores. Quartz, as expected, and potassium feldspar are most 

abundant in siltstone. In cycle 5, the larger amounts of 

quartz (34-42 peak height) (fig. 8A) in the northern part of 

the basin and in the Norton core are the result of clastic 

silt-size grains whose sorting and rounded morphology suggest an eolian origin such as those grains observed in some 

of the halite beds. On the other hand, the larger amounts of 

quartz (33 peak height) in cycle 3 in the southern part of the 

basin are due to recrystallized sponge spicules. As expected, 

argillaceous shale contains the most clay and plagioclase. In 

cycle 5, clay (13 peak height) is most abundant in the 

south-central part of the basin, whereas in cycle 3, amounts 

of clay are relatively uniform across the basin (fig. 85). In 

cycle 5, plagioclase is most abundant (20 peak height) in the 

southwestern part of the basin, whereas potassium feldspar is 

most abundant along transect B-B' (18-22 peak height). In 

cycle 3, plagioclase is most abundant (13-14 peak height) in
Table 6. Means of selected chemical parameters and sulfur isotopic compositions by rock type and by core and cycle, Pennsylvanian Paradox 

[Standard deviations in parentheses, n, number; 

that are representative of the entire interbed]

^. inorganic carbon; C()rg, organic carbon; HI, hydrogen index; Srjj, disulfide sulfur; Ferct, reactive iron; DOPr, degree of pyritiza

Rock type

Dolostone

Argillaceous sh

Dolomitic sh

Calcareous sh

All rock types

Core

(cycle)

Shafer (3)

Shafer (5)

Gib son Dome (5)

Crowley Ranch (5)

Duncan Tevault (5)

Norton Federal (3)

Norton Federal (5)

Woods (5)

Ute Mountain (3)

Lake Canyon (3)

T^ipLrptt TTpHpfjil (^\

West Water Ck. (3)

State(3)

State (5)

Elk Ridge (3)

Elk Ridge (5)

Honaker Trail2 (5)

Geometric mean. 

2Outcrop sample.

Cco3 

(wt%)

8.0(2.3).,,

8

-3 /I 7\ 

 3 (1. /) 

3.9(1.4).,,

2.2 (.79).,,

4.8(1.0).,,

4.4 (.91).,,

4.9(2.5),,.

Cco3 

(wt%)

4 2 (2 5)

6.0(5.6).,,

4.9(1.5).,,

4.5(1.9).,,

4.0.,,

3.6(2.7).,,

5.6(4.3).,,

6.0(3.4).,,

5.5 (.9).,,

5.9(2.0).,,

3 9 (2 1 )

5.1 (2.5).,,

4.5 (.6).,,

6.6(3.9).,,

5.8(3.0).,,

5.3(1.0).,,

3.7(1.7).,,

3.7.,,

C0rg

(wt.%1 ;

.,,0.62.

.,,0.38.

.,,0.18.

,,,.2.7.

.,,,1.2.

.,,,2.0.

.,,,1.1.

C0rg

(wto/o1 ;

....... 1.5.

.......2.6.

.......1.3.

.....0.10.

.......1.9.

.....0.91.

.......1.3.

.....0.91.

.,,0.99.

.....0.81.

.......1.3.

....... 1.7.

....... 1.4.

.......2.0.

.....0.16.

....... 1.1.

....... 1.8.

.......2.2.

.......6.8.

n 

)

,22

,19

,14

,33

,11

,51

150

n

)

,29

...A

,15

,,7

....2

...A

...A

,10

,,8

,,9

,,8

,13

,,6

...A

....6

,,6

,,7

,,7

....1

HI n

210(122), .14

76 (100), .14

113 (159), ...5

236 (146), .29

245 (174), .14

177 (147), .49

186 (148). 120

HI n

301 (87), .25

340 (86). ....3

382 (51), .12

.....0

22. ,,2

42 (8), ...4

51 (8).. ...4

28 (20),, .5

44 (21), ...8

12(5). ....9

72 (18), ...8

58 (21), .13

80 (29), ...6

.....0

328 (40), ...4

296 (26). ....6

465,,.!

SDi 

(wt%)

0.70.

1.2.

0.52.

1.3.

0.98.

1.4.

1.2.

SDi 

(wt%)

1.1 (.5).

0.28.

1.1 (.4).

2.0.

1.1 (.31).

0.58 (.42).

0.83 (.11).

1.7(1.7).

20(1)

1.9.

0.54 (.43).

1.6(1.0).

12(2)

0.89.

n

1?

9

10

3?

6

47

116

n

19

?

15

?

3

7

7

6

4

?

5

5

7

,,1

834SDl

-22.5(11).,

-19.9(7).,

-19.0(12).,

-24.6(7).,

-27.2(7).,

-19.2(7).,

-21.7(8).,

s34c 

d »Di

-25.5 (7)...

-37.9,.

-17.8.,

-30.2.,

-29.7(4),.

-14.3(2).,

-28.1 (8)...

-27.7.,

-16.0(4),.

-20.2(4).,

-17.9(5).,

-16.4(3).,

-22.9,.

-23.5(3).,

-8.3 (4)...

-18.7.,

-21.4...

n

7

7

77

4

34

82

n

19

9

0

3

4

7

7

6

9

4

5

5

2

0

...1

Ferct 

(wt%)

10(5)

1.3(1.6),

0.90 (.58),

2. 3 (.67),

2.0 (.50),

Ferct 

(wt%)

2 2 ( 7)

1.0,

0.91 (.28),

2.6,

1.8 (.4),

1.2 (.6),

1.3 (.2),

2.4(1.4),

26(1)

2.1,

0.76 (.57),

1.7(1.0),

2.2(1.1),

0.61,

n

13

9

10

3?

47

117

n

19

7

7

?

3

7

7

6

4

?

5

5

7

...1

DOPr

0.47 (.28

0.68 (.09)

0.52 (.16

0.49 (.11

0.46 (.13)

0.59 (.11

0.54 (.16)

DOPr

0.42 (.11

0.2

0.54 (.13)

0.6

0.52 (.05

0.63 (.03

0.36 (.19

0.56 (.02

0.57 (.04)

0.56 (.16)

0.57 (.03

0.68 (.02

0.7

0.66 (.08)

0.81 (.06)

0.63 (.13

0.61 (.14)

0.61
N12 EVOLUTION OF SEDIMENTARY BASINS PARADOX BASIN

25

20

C/) 1^ 

LJJ I0

X 

O

O 

c/)

b 10

3

o

o

0

~ 25 wt % Clay

n oia n 

n DO OTJ a 

a o

0 4 8 10 12

CARBONATE CARBON, IN WEIGHT PERCENT

EXPLANATION

14

 Argillaceous shale

n Dolomitic shale

O Calcareous shale

x Siltstone or sandstone

rj Limestone

O Dolostone

B Shaly to silty limestone

^ Shaly to silty dolostone

O Anhydrite

H Halite
GEOCHEMISTRY OF TWO INTERBEDS, PENNSYLVANIAN PARADOX FORMATION, UTAH AND COLORADO N13

Figure 7 (previous page). Crossplot of total clay (X-ray diffraction peak heights in units of 0.1 inch) versus carbonate carbon 

(Cco?) (weight percent) for cycles 5 and 3 of the Pennsylvanian Paradox Formation showing lithologic fields. See text for explanation.

the central part of the basin, and potassium feldspar is most 

abundant (13 peak height) in the northern part of the basin 

(figs. 8C, SD).

Calcite is generally most abundant in the southern part 

of the basin in shelf or near-shelf facies and in cores containing the smallest amounts of dolomite (figs. 8E, 8F). An 

exception is cycle 5 in the Elk Ridge core in which both 

amounts of calcite and dolomite are present in small 

amounts. In shale, calcite is generally micritic, although 

shell fragments are locally abundant. Limestone contains 

abundant shell fragments. In cycle 5, dolomite (115-160 

peak height) is most abundant along transect B-B' (fig. 8F), 

and in cycle 3, dolomite is most abundant in the most northerly core (90 peak height). Dolostone comprises predominantly fine silt sized dolomite rhombs with some shell 

fragments.

CLASTIC SEDIMENTATION

Patterns of interbed thickness and sources of clastic 

sediment are significantly different for cycles 3 and 5, as 

shown in the isopach maps for the interbeds of the two 

cycles (fig. 5). The interbed of cycle 5 is much thinner than 

that of cycle 3, and three clastic sources are likely for cycle 

5: a southwesterly source relatively rich in clay and plagioclase and poor in quartz, an easterly source relatively rich in 

quartz and potassium feldspar and poor in clay, and possibly 

a source-of silt-sized quartz carried into the basin by winds 

from the north, the dominant wind direction in the basin during Middle Pennsylvanian time (Driese and Dott, 1984). 

These various clastic sources are proposed to explain the 

petrographic data and trends in the maps of relative mineral 

amounts (peak-height means, figs. 8A-8D). Note that the 

amount of plagioclase and, to some extent, potassium feldspar may be controlled in part by the salinity of pore water 

and diagenesis, an effect that is discussed later.

The interbeds of cycle 3 thicken dramatically to the 

northeast, where the basin was rapidly subsiding in response 

to uplift of the Uncompahgre highland (fig. 5B). The lack of 

variation in mineralogy throughout the basin in cycle 3 suggests that the single major source of clastic material during 

deposition of cycle 3 was the Uncompahgre highland.

AUTHIGENIC MINERAL PRECIPITATION

Chemical sediments in interbeds of the Paradox 

Formation include calcite, dolomite, anhydrite, and halite.

Carbonate minerals are ubiquitous in the sampled cores and 

were detected in all rock types. The overall amount of carbonate carbon in the interbeds is independent of carbonate 

mineralogy (calcite or dolomite), except in areas within the 

basin dominated by argillaceous shale, which contains 

markedly less carbonate. The relative absence of carbonate 

in shale is attributed to either a decrease in carbonate supply 

during deposition or to a lack of carbonate formation during 

diagenesis. Thin-section observations show more calcareous bioclasts in calcareous shale relative to argillaceous 

shale, which supports the first hypothesis. The sulfur-isotope data, as discussed in the section Pyrite Formation, suggest that, in some parts of an interbed, sulfate reduction 

occurred after burial. Bicarbonate is produced during sulfate reduction and can react with available cations to form 

carbonates, one process consistent with the second hypothesis.

The amount of dolomite in interbeds across the basin 

may be related to the areal extent of the halite in each cycle. 

Large amounts of dolomite are restricted to cores in which 

the interbed is overlain by halite (as shown by superimposing figs. 4 and 8F). Therefore, we attribute the distribution 

of abundant dolomite to downward movement of brines 

during halite deposition. Halite-saturated brines have the 

large Mg:Ca ratio needed for dolomitization of calcite or 

aragonite (Bathurst, 1971). The cycle-3 interbed in the Gibson Dome core was deposited near the edge of halite distribution for that cycle (fig. 4fi), and abundance of dolomite 

only in the upper two-thirds of the interval suggests that 

movement of the dolomitizing brine was limited to the 

upper part of the interbed.

The preceding hypothesis implies that much of the carbonate in the basin was originally deposited as calcite, in the 

form of shell fragments, micrite cement, and carbonate 

grains transported off the shelf at the onset of transgression, 

although some calcite formed during diagenesis. The pervasive dolomitization of some shale and dolostone probably 

occurred during very shallow burial. This hypothesis is 

consistent with the concentrically zoned dolomite rhombs 

observed in thin section. Large halite veins are present only 

in samples containing abundant dolomite, further evidence 

that a halite-saturated brine moved through the sediment 

after some compaction. On the other hand, small veinlets of 

halite are present in many of the argillaceous shale samples 

in which calcite is the dominant carbonate mineral. Dolomitization of the calcite within these shales may have been 

inhibited by organic films derived from their associated 

abundant organic matter. (For a discussion of this phenomenon see Bathurst, 1971.)

Small amounts of anhydrite are present in most interbed samples that are overlain by anhydrite. Some of the 

anhydrite is vein filling and some is present as disseminated 

crystals in the rock matrix. Vein-fill anhydrite is related to 

postdepositional movement of brines through the interbeds. 

One 5-m-thick interval of anhydrite was deposited in the
N14 EVOLUTION OF SEDIMENTARY BASINS PARADOX BASIN

N

i \

D

Figure 8 (above and facing page). Maps of means (X-ray diffraction peak heights in units of 0.1 inch) of minerals in individual cycles 

and cores. Circles with lower half filled indicate cycle 5 core samples representative of entire interbed; circles with upper half filled indicate 

cycle 3 core samples representative of entire interbed; filled circles indicate samples from cycles 5 and 3 representative of respective interbeds; open circles indicate samples from cycles 5 and 3 not representative of respective interbeds. Solid type represents data for cycle 3; 

screened italic type represents data for cycle 5. A, quartz. B, clay. C, sodium feldspar. D, potassium feldspar. E, calcite. F, dolomite.

middle of the cycle-5 interbed in the Shafer core, and thin 

beds (<1 m) of anhydrite also are present in the Gibson core. 

The accumulation of bedded anhydrite within the interbed of

cycle 5 indicates that maximum salinity in the center of the 

basin was greater during deposition of the cycle-5 interbed 

than during deposition of the cycle-3 interbed.
GEOCHEMISTRY OF TWO INTERBEDS, PENNSYLVANIAN PARADOX FORMATION, UTAH AND COLORADO N15

F

ORGANIC GEOCHEMISTRY

ORGANIC-MATTER DATA

Mean values for organic carbon (Corg> in weight 

percent) and hydrogen index (HI) for the various lithofacies

and cores (by cycles) are given in table 6. The amounts of 

organic carbon in cycle 3 (mostly limestone) of State core 

("S," fig. 1) and cycle 5 (mostly siltstone) of Gibson core 

("G," fig. 1) are 0.16 and 0.10 weight percent, too small to 

determine a hydrogen index. Except for these two cores, 

organic carbon in both cycles decreases from the shelf facies 

into the basin along transect A-A' and increases from the 

shelf facies into the basin along transect B-B' (fig. 9A). 

Hydrogen indices in adjacent cores are similar between 

cycles and follow the same trends as organic carbon (fig. 

9B). The dividing line between large (>200) and small 

(<100) hydrogen indices is about 30 km west of the Colorado-Utah State line between the Aztec and West Water 

Creek core holes ("A" and "WW," fig. 1).

A map of core means of Tmaxis not presented because 

Tmax values for some samples are suspiciously small compared to those in adjacent samples, and similar organic matter within narrow depth intervals should reflect similar 

maturation. Migrated bitumen can cause unusually low 

Tmax values (Whelan and Thompson-Rizer, 1993), and oil 

staining was observed in some thin sections.

PRODUCTIVITY, PRESERVATION, AND MATURATION 

OF ORGANIC MATTER

An implicit assumption in the study of organic matter 

in sedimentary rocks is that the amount and type of organic 

matter analyzed is dependent on four variables: the transport of terrestrial organic matter into the depositional basin, 

primary productivity, preservation during sedimentation 

and early diagenesis, and maturation of hydrocarbons during burial to generate petroleum. (For a discussion of the 

role of these processes see Tissot and Welte, 1984, and 

Engel and Macko, 1993.) Hite and others (1984) and, to a 

lesser extent, Hite and Anders (1991) discussed a variety of 

organic-chemical results used to evaluate the effects of these 

variables on the organic geochemistry of Paradox Formation interbeds. Most of their samples were from cores along 

the western part of the basin where maturation for any one 

stratigraphic unit should be more or less constant. They proposed that the interbeds contain a mixture of marine and 

coaly (terrestrial) organic matter and that organic matter 

preservation was enhanced in a sulfidic (^S-bearing), 

saline depositional environment. They indicated that oil 

migration from shale sealed above and below by evaporites 

is negligible but that oil did migrate from shale where such 

seals are not present.

The east-to-west increase in hydrogen index values 

(fig. 9B} reflects differential organic matter maturation, 

migration of hydrocarbons, and (or) differences in the proportion of kerogen types. Burial reconstruction using vitrinite reflectance data (Nuccio and Condon, in press) and Tmax 

values show that the sediments in the southeasternmost part 

of the basin are overmature with respect to petroleum 

generation and maturation decreases to the west. This
N16 EVOLUTION OF SEDIMENTARY BASINS PARADOX BASIN

B D

Figure 9 (above and facing page). Maps of means of selected chemical parameters in individual cycles and cores of cycles 5 and 3 of the 

Pennsylvanian Paradox Formation. Circles with lower half filled indicate cycle 5 core samples representative of entire interbed; circles with 

upper half filled indicate cycle 3 core samples representative of entire interbed; filled circles indicate samples from cycles 5 and 3 representative of respective interbeds; open circles indicate samples from cycles 5 and 3 not representative of respective interbeds. Solid type represents data for cycle 3; screened italic type represents data for cycle 5. 4, organic carbon (Corg) (weight percent). B, hydrogen index (HI) 

(mg HC/g Corg)- C chromium (Cr) (parts per million). D, nickel (Ni) (parts per million). £, disulfide sulfur (Spj) (weight percent). F, 

(per mil). G, reactive iron (Fe,-ct) (weight percent). //, degree of pyritization (DOPr).
GEOCHEMISTRY OF TWO INTERBEDS, PENNSYLVANIAN PARADOX FORMATION, UTAH AND COLORADO N17

pattern is consistent with maximum subsidence of the basin 

along the front of the Uncompahgre uplift (Stevenson and 

Baars, 1987; Huffman and Condon, 1993) and burial beneath 

a thick Permian section (Cater, 1970). The coincidence of 

small hydrogen index values in thermally overmature parts 

of the basin and large hydrogen index values in parts of the 

basin in, or just entering, the oil window suggests that thermal maturation plays a major role in the distribution of 

hydrogen index values across the basin. 

Mixing of kerogen types also contributes to the variability in hydrogen index values; that is, hydrogen index values

are low for terrestrial organics and high for algal-type organics. Mixing is evident from trends in hydrogen index values 

within the cycle-3 interval of the Shafer core. All samples in 

this interval have the same burial-thermal history and are just 

entering the oil-generating window (Hite and others, 1984; 

Nuccio and Condon, in press; Tmax values, this study). Vertical variation in hydrogen index values in the Shafer interval 

are attributed to mixing of terrestrial organic matter with 

marine-algal organic matter. Because degradation of organic 

matter during deposition and early diagenesis decreases the 

hydrogen index value, especially that of the algal-type
N18 EVOLUTION OF SEDIMENTARY BASINS PARADOX BASIN

Table 7. Means of trace metals in shales of Pennsylvanian Paradox Formation, Utah and Colorado.

[Average shale values from Wedepohl (1978); n, number of samples]

Metal

As

Cr

Mo1

Ni

Se

V

n

23

97

97

97

23

97

Range Arithmetic mean Standard 

(ppm) (ppm) deviation

4.2-23

24-580

<2-77

10-950

3-24

24-590

8.8

270

5.0

96

8.3

98

4.1

120

8.7

95

5.7

60

Geometric mean 

(ppm)

8.1

240

3.2

80

6.9

88

Concentration 

in average shale 

(ppm)

13

83

2.6

53

0.6

110

Statistics calculated by substituting 1 ppm for the 15 samples containing < 2 ppm Mo.

organics, the vertical variations may also represent an 

increase in preservation of organic matter upward through 

the core. Variability in hydrogen index values was not 

observed within cores from the southeastern parts of the 

basin. If originally present, the variability may have been 

obliterated by degradation or thermal maturation of the 

organic matter.

TRACE-METAL GEOCHEMISTRY

TRACE-METAL DATA

The geometric means of chromium and nickel concentrations vary among rock types (table 6). All shale types 

have high mean concentrations (150-280 ppm Cr, 61-98 

ppm Ni), whereas limestone, dolostone, and siltstone have 

lower mean concentrations (25-40 ppm Cr, 12-20 ppm Ni). 

Dolomitic shale (150 ppm Cr, 61 ppm Ni) has less chromium and nickel than calcareous or argillaceous shale (230 

and 280 ppm Cr, 74 and 98 ppm Ni). No significant difference was detected in chromium and nickel contents between 

cycle-5 and cycle-3 interbeds, and variations among cores 

are not sufficiently systematic to identify trends within the 

basin (figs. 9C, 9D).

TRACE-METAL ENRICHMENT

Trace-element concentrations can be used to define 

geochemical conditions during carbonaceous rock 

deposition (Calvert and Pedersen, 1993). In table 7, average 

trace-element contents of Paradox Formation shale are 

compared to the mean abundance in average shale as 

defined in the compilation by Wedepohl (1978). The 

Paradox shales contain much more chromium, nickel, and 

selenium than average shale. Other elements commonly 

enriched in carbonaceous shale, such as arsenic, 

molybdenum, and vanadium (Vine and Tourtelot, 1971), 

have mean contents in Paradox Formation shale that are not 

significantly different from average shale (table 7).

Concentrations much higher than the mean values for all 

these metals were measured in a few samples.

The amounts of chromium and nickel added to Paradox sediments by geochemical processes were estimated by 

subtracting the allochthonous component from the 

whole-rock concentration. These calculations of enriched 

values are subject to major assumptions, including a chemically homogeneous detritus and limited metal redistribution during diagenesis. Nonetheless, enriched values more 

directly reflect processes affecting interbed composition 

than do total concentrations.

Allochthonous detritus in Paradox interbeds is 

assumed to have originated from source areas that were 

chemically similar because variations in mineralogy across 

the basin are not evident in the abundances of most 

elements. For example, the constancy of the source areas is 

consistent with the similar Al:Ti ratios in limestone, 

dolostone, siltstone, dolomitic shale, and argillaceous shale. 

Ratios of Al:Ti range from 18 to 21 and have correlation 

coefficients greater than 0.92 for these rock types. Aluminum and titanium are mostly bound to phases that are relatively unreactive in marine environments; therefore, both of 

these elements provide a good estimate of the amount of 

allochthonous detritus.

The amounts of chromium and nickel attributed to the 

allochthonous detritus were estimated by plotting chromium and nickel concentrations as a function of aluminum 

content (figs. 10A, IOB). Samples that have the lowest 

chromium and nickel concentrations relative to aluminum 

are considered to be samples in which depositional and 

diagenetic enrichment of the metals was small. This subset 

of the data was used to define the expected background concentrations as a function of aluminum content. Note that the 

background lines define slopes similar to the ratio expected 

for average shale. The amount of metal expected to be in 

allochthonous detritus, based on the aluminum content, was 

then subtracted from the whole-rock concentration to 

estimate the amount of element enrichment for both 

chromium and nickel. Calculated maximum enrichments 

are almost 500 ppm chromium and 150 ppm nickel.
GEOCHEMISTRY OF TWO INTERBEDS, PENNSYLVANIAN PARADOX FORMATION, UTAH AND COLORADO N19

600

|j 500-

CC 

UJ 

Q- 400

< 300 -

Q_

0 0

°o °

Vo o° 

o00<B$<»n ° °°

8 9

200

175

150

cc

£ 125

OT

fe 1QO

0 0 0 (BO 

0 OD

000 0 

0 OD Q 

0 0 000 00 

0 §00

^ -JTlfM 1 I t*T ft.

23456789 

B ALUMINUM, IN WEIGHT PERCENT

Figure 10. Crossplots of chromium 04) and nickel (B) versus aluminum for samples in study. See text for derivation of lines. 

Average shale values are from Wedepohl (1978).

The amounts of enriched chromium (Crenrjch) and 

enriched nickel (Nienrjch) are shown as a function of organic 

carbon in figures 1 1A and 1 IB. The linear distribution of the 

data indicates that organic matter accumulation and preservation and accumulation of the metals are related. A few 

dolostone and siltstone samples that contain moderate to 

large amounts of organic carbon are notable for their lack of 

metal enrichment. One of these samples contains migrated 

bitumen. The low chromium content of this sample is consistent with the small concentrations of chrorriium in petroleum (Barwise and Whitehead, 1983; Curiale, 1987). Other 

samples that have low metal contents relative to the amount 

of organic matter may also contain migrated hydrocarbons. 

Correlation coefficients of organic carbon versus enriched 

chromium and enriched nickel are 0.91 and 0.92, respectively, if the samples having low metals content and high 

organic-carbon content are excluded. Scatter away from a 

simple linear trend is attributed to spatial and temporal variations in the depositional environment and to organic-matter 

loss during oil and gas generation.

Trace elements originally dissolved in seawater 

accumulate in marine sediments through a range of possible 

processes (Breit and Wanty, 1991). Retention of these 

elements in the sediment requires geochemical conditions 

that inhibit cycling of the metals from the sediments back

into the overlying water column (Shaw and others, 1990). 

The chemical conditions during deposition of the Paradox 

interbeds can therefore be estimated based on the metals that 

are most strongly enriched in carbonaceous rocks (Shaw and 

others, 1990; Emerson and Huested, 1991). Chromium, 

nickel, and selenium, the elements most enriched in the Paradox interbeds, accumulate in moderately to strongly reducing environments (Shaw and others, 1990). In contrast, 

arsenic, molybdenum, and vanadium, which are not enriched 

in the Paradox interbeds, are most enriched in strongly reducing sulfidic environments. The moderately reducing environment is envisioned to be capable of preserving organic 

matter but is devoid of t^S until some depth below the sediment-water interface.

The weight ratio of enriched metal to organic matter in 

the Paradox interbeds is two to four orders of magnitude 

greater than the ratio found in modern organisms (Breit and 

Tuttle, 1994). Therefore, the ratio in the sediment requires 

either additional abiogenic mechanisms of chromium and 

nickel accumulation or the loss of more than 99.9 percent of 

the deposited organic matter. Alternative mechanisms of 

metal accumulation include diffusion into the sediment 

(Brumsack and Gieskes, 1983) and adsorption of metals onto 

organic and inorganic particles settling through the water 

column (Balistrieri and others, 1981). To account for chromium enrichments of more than 200 ppm in the Paradox 

interbeds, considering the small chromium concentrations of 

seawater (0.3 |ig/kg; Quinby-Hunt and Turekian, 1983), a 

column of seawater several hundred meters high would have 

to pass through the sediment. Such a volume is inconsistent 

with both the preservation of organic matter and the sulfur 

isotope systematics of the chromium-enriched rocks. Accumulation by settling particles is a more reasonable explanation.

Ratios of enriched chromium to enriched nickel in the 

interbeds are variable and range from 0.3 to 25. For the shale 

samples, the ratio ranges from 0.35 to 7.7, and mean values 

are from 3.1 to 4.2. These ranges are attributed to variations 

in chemical conditions during deposition. Previous studies 

of modern and ancient sediments indicate that chromium is 

likely to accumulate and be retained in sediments in which 

organic matter is preserved (Shaw and others, 1990); however, nickel tends to accumulate in oxic sediments containing 

manganese oxides (Shaw and others, 1990) or is predicted to 

accumulate in sediments in which F^S favors incorporation 

of nickel into sulfide minerals (Lewan, 1984). In moderately 

reducing sediments, nickel is cycled from the sediments into 

the overlying water because sulfide and manganese oxides 

are absent. Therefore, we interpret high ratios of enriched 

chromium to enriched nickel to indicate moderately reducing 

conditions near the sediment-water interface, whereas low 

ratios indicate more reducing conditions that favor sulfate 

reduction. Detailed analysis of the temporal variations in this 

ratio for cycle 3 of the Shafer core is presented in a later 

section.
N20 EVOLUTION OF SEDIMENTARY BASINS PARADOX BASIN

Crenrich (PP m ) = 77 x C Org (wt.%) 

r = 0.91

250

200

Nj enrich (PP m ) = 20- 8 x C Org 

r = 0.92

UJ

= 150

Q UJ

O h-

"^ Q100

50

LLJ

£ 0

-50

B

2 4 6 8 10 12 

ORGANIC CARBON, IN WEIGHT PERCENT

EXPLANATION

0 Dolostone O Calcareous shale

D Argillaceous shale + Siltstone

A Dolomitic shale X Limestone

Figure 11. Crossplots of enriched chromium (A) and enriched nickel (B) versus organic carbon for samples in study by 

rock type.
GEOCHEMISTRY OF TWO INTERBEDS, PENNSYLVANIAN PARADOX FORMATION, UTAH AND COLORADO N21

SULFUR AND IRON GEOCHEMISTRY

SULFUR PHASES AND THEIR ISOTOPIC COMPOSITION

Disulfide sulfur (So,; sulfur in FeS2) makes up 78 percent of the total sulfur in all but the anhydrite samples. The 

means of disulfide sulfur (weight percent) and its isotopic 

composition (634Srji %c) for the different rock types and the 

different cores (by cycles) are presented in table 6. Argillaceous and calcareous shale have the largest means for disulfide sulfur. In cycle 5, the smallest means (0.28-0.58 

weight percent) are in the northern part of the basin and in 

the Norton core (fig. 9£). In cycle 3, means are relatively 

similar among cores (0.83-1.3 weight percent), except for 

the high value (1.9 weight percent) in the West Water Creek 

core and the low value (0.54 weight percent) in the State 

core. The dominant disulfide mineral is pyrite, which is 

present as framboids, infilled framboids, anhedral and euhedral grains, and replacement of shells and sponge spicules 

(fig. 12).

534Soj values among the rock types are similar (-19.0 

%c to -24.6 %c), except that for dolomitic shale, which has a 

very negative 634Srji mean (-30.4 %c). Cores along the 

cycle-5 transect B-B' have similarly negative values (-28 %c 

to -38 %c\ fig. 9F). These very negative values reflect either 

slow bacterial sulfate-reduction rates (large isotopic 

fractionation factor) or a large, continuous supply of sulfate 

during sulfate reduction. Relative to many of the mean 

834Srji values in cycle 5, mean values for cores of cycle 3 are 

less negative (-14 %c to -26 %c), indicating either faster 

reduction rates or smaller sulfate reservoirs during reduction.

Sulfate was detected in almost all samples (Appendix 

2). 634Ssc>4 values of <0 %c suggest oxidation of a sulfide 

phase as the sulfate source. Pyrite could have oxidized during sample handling. Alternatively, sulfate could be the 

result of oxidation of H2S during diagenesis. Sulfate that 

has a 834Ssc>4 value similar to that of bedded anhydrite (+12 

%c to +17 %c) probably was derived from sulfate in the water 

column or from migrating brines.

IRON AND ITS DEGREE OF PYRITIZATION

Reactive iron (iron soluble in hot 6 M HC1 plus iron in 

makes up more than 86 percent of the total iron in all 

but the anhydrite samples (Appendix 2). The means for 

reactive iron (weight percent) and its degree of pyritization 

(DOPr) for the various rock types and cores are given in 

table 6. Similar to means for disulfide sulfur, the highest 

means for reactive iron are for argillaceous and calcareous 

shales. In cycle 5, the highest means are for the west half of 

transect A-A' (fig. 9C). In the northern part of the basin,

mean reactive iron values for cycle 5 are half those for cycle 

3. Mean values for cycle 3 increase from the shelf into the 

basin along transect B-B' (1.3-2.2 weight percent). The 

highest mean for cycle 3 (2.4 weight percent) is in the middle of the southern part of the basin along transect A-A'.

Mean values for degree of pyritization are generally 

comparable among rock types, with the exception of a 

somewhat higher mean value (0.68) for limestone. In the 

northern part of the basin and in the Norton core (fig. 9f/), 

mean values are the smallest (0.25-0.39). In the remainder 

of the southern cores, means are generally comparable 

between cycles and among cores (0.52-0.68), except for 

means for two of the shelf cores, which are larger (0.78 and 

0.81).

PYRITE FORMATION

In the interbeds, the content of sulfur in disulfide minerals such as pyrite (Srji) is proportional to amounts of reactive iron (Srji and Ferct correlate with r = 0.86; fig. 13). If 

the amount of reactive iron sulfidized is considered (degree 

of pyritization, DOPr), the amount of disulfide sulfur in the 

interbed can be expressed from this stepwise regression 

equation

SDi (wt%) = -1.1 + 0.68 x Ferct (wt%) + 1.9 x DOPr 

(r=0.96)

The amount of reactive iron parallels that of clay (r = 

0.84), indicating that a primary reactive iron source to the 

sediment was probably iron-oxyhydroxide coatings on 

fine-grained particles. Such oxides are generally quite reactive to H2S (Schoonen and Barnes, 1991). Because the 

amount and reactivity of iron ultimately controlled the 

amount of pyrite in the Paradox Formation interbeds, disulfide sulfur concentrations are not proportional to 

organic-carbon concentrations, as is the case for normal 

marine sediments (Sweeney, 1972).

Much of the data shown in figure 13 clusters near the 

stoichiometric FeS line. The predominant morphology of 

the sulfides in a given sample is predictable from where the 

sample plots relative to the FeS line. Samples that plot 

below the FeS line have DOPr values <0.50 and contain predominantly framboidal pyrite, whereas those between the 

stoichiometric FeS and FeS2 lines (DOPr = 0.50-1.0) contain dominantly infilled framboids, euhedral or anhedral 

grains, or pyrite masses that replace shell fragments, sponge 

spicules, and tests.

Framboids are generally thought to be one of the first 

pyrite morphologies to form in sediment. They form by 

reaction of F^S with reactive iron-oxyhydroxides to 

produce an unstable FeS phase that eventually converts to 

pyrite (Sweeney and Kaplan, 1972; Raiswell, 1982). 

Infilling of pyrite framboids (described in Love and 

Amstutz, 1966); growth of euhedral pyrite grains; and 

pyrite replacement of shells, spicules, and tests are thought
N22 EVOLUTION OF SEDIMENTARY BASINS PARADOX BASIN

Figure 12. Photomicrographs of pyrite morphologies, reflected light in oil. Field of view 0.27 mm. A, framboids, Shafer core, 780.9-m 

depth. B, infilled framboids, Pickett Federal core, 1,726.4-m depth. C, euhedral, Crowley Ranch core, 1,802.9-m depth. D, replacement 

within shell, Pickett Federal core, 1,726.4-m depth.

to occur during deeper burial and may depend on the slow 

release of iron from more recalcitrant mineral phases 

(Raiswell, 1982; Canfield and others, 1992). The sulfur 

isotopic composition of pyrite can indicate conditions of 

pyrite formation and also help constrain the paragenesis of 

pyrite generations.

If seawater is the source of sulfate, the isotopic composition of sedimentary pyrite is controlled by three factors. 

First, the isotopic composition of the H2S that ultimately 

forms pyrite is dependent on the fractionation factor associated with bacterial sulfate reduction. The size of the fractionation factor is inversely proportional to the rate of 

reduction (Kaplan and Rittenberg, 1964), which, in turn, is 

a function of organic matter preservation and sedimentation 

rate (Goldhaber and Kaplan, 1975). As rates of sedimentation increase, so do rates of sulfate reduction (because of

enhanced organic-matter preservation), causing a decrease 

in the fractionation factor. The second factor is the size of 

the reservoir of available dissolved sulfate. The sulfate reservoir can decrease due to dilution, expulsion of pore water, 

or progressive sulfate reduction within a limited sulfate 

reservoir. As the sulfate reservoir decreases, a greater proportion of the sulfate is reduced, increasing the 834S of the 

H2S produced (limited sulfate supply, as described by 

Nakai and Jensen, 1964). The third factor is the relative 

flux of sulfate input and sulfate removal. For example, 

dissolved sulfate in isolated bottom water of a stratified 

water column will become progressively enriched in 34S 

because 32S is preferentially reduced in the water column 

by bacteria and removed to the sediment as pyrite (Holser 

and Kaplan, 1966). This condition can be sustained only if 

the sulfate input rate into the system is similar to the sulfate
GEOCHEMISTRY OF TWO INTERBEDS, PENNSYLVANIAN PARADOX FORMATION, UTAH AND COLORADO N23

0.5 1.0 1.5 2.0 2.5 3.0 3.5 

REACTIVE IRON, IN WEIGHT PERCENT

EXPLANATION

Infilling, euhedral, anhedral, 

and replacement pyrite

Framboidal pyrite

Figure 13. Crossplot of disulfide versus reactive iron for samples 

from cycle 5 (circles) and cycle 3 (x's) of the Pennsylvanian 

Paradox Formation showing fields of dominant pyrite morphology. 

Stoichiometric lines for pyrite (FeS2) and monosulfides (FeS) are 

included for reference.

removal rate. If a significant proportion of sulfate is reduced 

continually, the isotopic composition of the H2S, hence 

pyrite, produced can evolve to 834S values much greater 

than those of the original dissolved sulfate (Tuttle and Goldhaber, 1993). This process can also produce pyrite of varying 634Srji values, depending on the depth at which it forms 

in the water column (Tuttle and others, 1990; Saslen and others, 1993). The relative importance of these three controlling factors varies between cycles 3 and 5, among cores 

within a cycle, and within a single cycle, as indicated by 

cycle 3 of the Shafer core.

Interbeds from cycle 5 have a range of 834Srjj and 

degree of pyritization values because of variations in the 

conditions of sulfide formation. Both 534Srjj and degree of 

pyritization increase systematically to the southwest along 

transect A-A' (fig. 14). At the northeast end of the transect, 

at Duncan Tevault, 534Srjj values range from -33 %c to -23 

%c, whereas at the southwest end, the State samples have 

values from -15 %c to -5 %c. Degree of pyritization values 

increase from 0.5-0.6 in the north to 0.7 and 0.9 in the south. 

Cores from this cycle that underlie the halite (Shafer core) 

and anhydrite (Crowley Ranch, Duncan Tevault, and

-10

-20

cc LU

Q.

6-30

CO

-40

-50

r= 0.84

0.2 0.4 0.6 0.8 1.0

DEGREE OF PYRITIZATION 

EXPLANATION

+ Aztec Federal No. 1

 Crowley Ranch No. 1

 Duncan Tevault No. 1

O Honaker trail outcrop

A Norton Federal No. 1 -4

X Pickett Federal No. 1-33

0 Shafer No. 1

D State No. 1-16

A Woods Unit No. 1 -S

Figure 14. Crossplot of S34Srjj versus degree of pyritization 

(DOPr) for samples from cycle 5 of the Pennsylvanian Paradox 

Formation. Circled points are excluded from the regression 

analysis.

Norton cores) from the northern end of the transect have 

834Srji values from -27 %c to -40 %c and degree of pyritization values <0.55. These large negative 834Srjj values and 

relatively low degree of pyritization values are typical of 

sulfides that form near the sediment-water interface in 

anoxic sediments if rates of sedimentation are slow and an 

infinite sulfate reservoir is available (Goldhaber and 

Kaplan, 1974, 1975). The change in both parameters to the 

south is consistent with reduction of sulfate in buried sediment. Under conditions of burial, the sulfate reservoir is 

isolated from sulfate in the overlying water column, and the 

H2S generated becomes progressively enriched in 34S as the 

proportion of the sulfate reservoir reduced increases. In 

addition, iron is released from less reactive phases during 

burial and reacts with available sulfide to produce a higher 

degree of pyritization. Increased depth of burial from north 

to south is consistent with the increasing thickness of the 

interbeds along transect A-A' (fig. 5A).

Cycle-3 shales from the southeastern part of the basin 

have 534Srjj values of about -15 %c. These values are 

attributed to isolation of the sulfate reservoir by rapid
N24 EVOLUTION OF SEDIMENTARY BASINS PARADOX BASIN

sedimentation. Higher sedimentation rates in this area are 

inferred from the greater thickness of the interbed (fig. 5B). 

Intermediate negative 534Srji values (-18 %c to -26 %c) in 

other parts of the basin indicate that bacterial activity during 

cycle-3 deposition was similar (on the average) to that in 

open-marine sediment, although 634Srji versus depth plots in 

the Shafer core show distinct isotopic evolution during cycle 

3; this evolution is discussed in the next section.

VARIABILITY WITHIN A 

BASIN-CENTER CORE

Profound temporal changes in basin depositional conditions are best recorded in cores from basin centers, where 

the effects of more local and rapidly fluctuating basin-margin conditions are minimized. In order to examine the 

effects of changes in basin-center depositional and early 

diagenetic conditions on geochemical parameters, the 

cycle-3 interbed between bedded anhydrite (originally 

deposited as gypsum) in the Shafer core that is close to the 

depositional center of the basin (fig. 1) was sampled at a 

smaller interval than interbeds in other cores. Twenty-nine 

samples were collected from this 18-m-thick interval. The 

interbed lithology varies from bottom to top from 

dolostone (possibly deposited as calcite) and siltstone, to 

argillaceous shale with thin beds of shaly dolostone, then 

back to dolostone (Appendix 1). Selected element concentrations, sulfur isotopic data, and other geochemical parameters are profiled in figure 15. The trends within these 

profiles indicate that conditions throughout deposition and 

diagenesis of the cycle-3 interbed were dynamic and that 

change occurred on several different time scales.

In general, organic-carbon concentration and hydrogen 

index (figs. 15A, 15B) increase systematically upward 

through the interval to a maxima at 774-m depth (5 weight 

percent and 430 mg/g, respectively), then decrease in the 

upper 4 m of the profile, which is composed of dolostone; 

values for dolostone are always less than those for adjacent 

shale. Because the thermal maturity is the same throughout 

this interval, the variability in hydrogen index probably 

results from either a change in the source of the organic matter or a change in preservation during deposition. The proportion of terrestrial and algal organic matter probably plays 

a greater role than preservation for reasons discussed in the 

following section.

No systematic change of disulfide sulfur values with 

depth is evident in the profiles (fig. 15C); however, values 

for shale are higher than those for adjacent dolostones and 

are higher in the upper part of the interval. Samples of shale 

having higher disulfide sulfur values also contain more reactive iron and higher degrees of pyritization (figs. 15D, 15E}. 

834SDi values increase systematically from 782-m to 775-m 

depth (-35 %c to -17 %c), then decrease systematically to the 

top of the profile (-38 %c) (fig. 15/0- This trend reflects a

progressive change from sulfate reduction very near the sediment-water interface, to reduction in sediment isolated from 

the overlying water column during burial, then back to 

reduction at the sediment-water interface. More disulfide 

sulfur (higher reactive iron and degree of pyritization values) 

formed in sediments in which sulfate was reduced during 

burial when the release of iron during diagenesis would have 

occurred at the same time as generation of the H2S.

Enriched chromium and enriched nickel values mimic 

the systematic increase in organic carbon above 782-m depth 

to maximum values of 380 ppm and 100 ppm, respectively 

(figs. 15C, 15H). Samples below 782-m depth are not 

enriched in either metal. The ratio of enriched chromium to 

enriched nickel does not vary systematically, and the 

dolostone within shale has ratios very similar to adjacent 

shale (fig. 157). Similar to the 634Srji data, the variations are 

attributed to changes in the depth at which Ir^S is generated. 

Ratios of less than 3 indicate depositional periods during 

which H2S was being generated very near the sediment-water interface and both chromium and nickel were 

retained in the sediment. Ratios of more than 3 indicate periods during which nickel, but not chromium, was recycled at 

the sediment-water interface because the redox front had 

moved deeper into the sediment.

Data for cycle 3 of Shafer core show that some 

geochemical parameters (Cotg, HI, SDI, Ferct, DOPr, 

Crenrjch, and Nienrjch) are dependent on rock type, whereas 

others (834SD; and Crenrjch:Nienrich ratios) are not. The 

variability of parameters within the core indicates that 

processes during deposition and early diagenesis of the 

interbeds slowly and systematically changed within the 

basin (fig. 15).

GEOCHEMICAL PROCESSES DURING

DEPOSITION AND DIAGENESIS OF

SHALES OF THE PARADOX

FORMATION

Shale within interbeds of the Paradox Formation is of 

special interest because it is a good petroleum source rock 

(high organic carbon and hydrogen index) and deserves special mention. Earlier in this report, we proposed that argillaceous, calcareous, and dolomitic shales have similar gross 

sedimentary characteristics. Calcareous shale has added bioclast carbonate material, and dolomitic shale is the result of 

postdepositional alteration of calcium carbonates during 

brine migration. On this basis, we can infer conditions of 

deposition and early diagenesis of identified shale populations using diagnostic geochemical parameters in a stratigraphic context.

The 35 samples of argillaceous shale that were analyzed for sulfur isotopic composition can be divided into 

two populations with respect to 834Srji values: 10 samples
GEOCHEMISTRY OF TWO INTERBEDS, PENNSYLVANIAN PARADOX FORMATION, UTAH AND COLORADO N25

CO 

DC 

LLJ

LLJ

Z

DEPTH,

-//u

-772

-774

-776 

-778

-780

-782

-784

-786

-Tftft

O

-Q

n D

: A o°DDD

O °

- u n

- 0 ^

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^

-770

-772

-774

<£ -776

LLJ

QJ -778

? -780

t -782

LLJ

Q -784

-786

-788

0

012345 

A ORGANIC CARBON, 

IN WEIGHT PERCENT

0

n

n

n

0

i i i i i i i i

.4 .8 1.2 1.6

DISULFIDE SULFUR, 

IN WEIGHT PERCENT

-770

-772

-774

8 -776

LLJ

UJ -778

?. -780

t -782 

LLJ

Q -784

-786

-788

0

0 0

9

0

0 100 200 300 400

B HYDROGEN INDEX, IN 

MILLIGRAMS HYDROCARBONS PER GRAM 

ROCK ORGANIC CARBON

-770

-772 _

-774

£ -776

LLJ

UJ -778

? -780

t - 782 

LLJ

Q -784

-786

-788

0

D 

D

0

n

0 .5 1 1.5 2 2.5 3

D REACTIVE IRON, IN 

WEIGHT PERCENT

3.5

Figure 15 (above and following pages). Depth profiles of selected chemical parameters in cycle 3 in the Shafer core by rock type. 

A. Organic carbon (Corg) (weight percent). B, hydrogen index (HI) (mg HC/g Corg). C, disulfide sulfur (Spi) (weight percent). D, 

reactive iron (Ferct ) (weight percent). E, degree of pyritiztion (DOPr). F, 534Soi (per mil). G, enriched chromium (Crenrjch) (parts 

per million). H, enriched nickel (Nienrjch) (weight percent). /, enriched chromium to enriched nickel ratio (Crenrjch:Nienrjch) for 

interbed dolostones and shales.
N26 EVOLUTION OF SEDIMENTARY BASINS PARADOX BASIN

0}

DC 

LU

LU

2

I

Q.

LU

Q

-//u

-772

-774

-776

-778

-780

-782

-784

-786

-Tftft

0

n

" D D

Q

n

o D D

n

0

S-,

^

+

A

i . i . i . i . t .

0 0.1 0.2 0.3 0.4 0.5 0.6

E DEGREE OF PYRITIZATION

OD

DC 

LU

LU

2

x"

Q.

LU

Q

-770

-772

-774

-776

-778

-780

-782 ,

-784

-786 l

-rr*ri

.0

9n

n n D

n n

A D

- 0 D °

; »/ "

L 1 1

-

0

I

i i i i i i i i i i i i i i i

G

0 100 200 300 400

ENRICHED CHROMIUM, 

IN PARTS PER MILLION

CO 

DC 

LU

LU

-770

-772

-774

-776

-778

 -780

I

t -782

LU

Q -784

-786

-788

. 0

D

D

n

0

_ O

A

-40 -35 -30 -25 -20 -15 -10

- 5 34 SD j, IN PER MIL

have values <-27 %c (shale group 1) and 25 samples have 

values >-27 %o (shale group 2). Only one argillaceous 

sample in the shale group 1 contains sodium feldspar and 

apatite; all contain relatively large amounts of potassium 

feldspar; eight have Crenrjch'Nienrjch ratios <3.0; and all 

have DOPr <0.56. Many samples in shale group 2

OD 

DC 

LU

H

LU

^

2

X

Q.

LU

Q

-770

-772

-774 

-776

-778

-780

-782

-784

-786

i

~rr\ r\

-0

:°oo

1 . ° Do QD °

L-L

- ° n

: °° "0°

h

-

0

i

0 20 40 60 80 100 120

H ENRICHED NICKEL, 

IN PARTS PER MILLION

contain plagioclase and apatite, have relatively small 

contents of potassium feldspar, and generally have 

Crenrich:Nienrich ratios > 3.0 and DOPr > 0.56. Argillaceous shale samples of group 1 are from cycle 5 and 

from the lower half of cycle 3 in the Shafer core. Argillaceous shale samples of group 2 are in all cores in both
GEOCHEMISTRY OF TWO INTERBEDS, PENNSYLVANIAN PARADOX FORMATION, UTAH AND COLORADO N27

-//O

-772

-774 

(S)

LJJ '776

^ -778

 -780

I

QL '782

LJJ

Q -784

-786

7QQ

O

-

cP

A

D

-

On

<^

. +

-

A

i i i

n

n

CP

A ^

D

i i i i

1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5

/ ENRICHED CHROMIUM/ 

ENRICHED NICKEL

EXPLANATION

0 Dolostone

n Argillaceous shale

A Dolomitic shale

O Calcareous shale

+ Siltstone

cycles except that they are not in cycle 5 of the Shafer 

core.

With respect to geochemical parameters discussed in 

the preceding paragraph, of the 32 calcareous shales analyzed for S34Soi, 28 are similar to the argillaceous shale of 

group 2. The three dolomitic shales for which isotopic 

compositions were determined are more variable and do not 

fit neatly into either the shale group 1 or 2, possibly because 

of postdepositional alteration.

Proposed conditions of shale deposition and diagenesis consistent with geochemical characteristics of the two 

shale groups are summarized in figure 16.

Shale group 1. As sea level rose at the onset of transgression, seawater entered the basin and a brine formed at 

the basin bottom through the dissolution of evaporites. The 

higher salinity of the brine created a pycnocline that separated the brine from the overlying seawater, and a stratified 

water column developed. Much of the organic matter accumulating in the sediment was terrestrial in origin, and the 

contribution from primary productivity was minor. Aided 

by the low oxygen content characteristic of brines (oxygen 

solubility decreases as salinity increases; Weiss, 1970) and

by restricted circulation from stratification, settling organic 

matter quickly established anoxic conditions at the 

sediment-water interface. Bacterial reduction of sulfate 

occurred at or directly below the sediment-water interface 

where sulfate was readily available from the overlying 

water column (infinite reservoir). Only the very reactive 

iron oxyhydroxides were available to form pyrite by reaction with the H2S being generated. The rate of sedimentation probably was slow, facilitating the diffusion of sulfate 

from the brine into the sediment. These conditions produced very 34S depleted iron sulfides. Sulfate reduction 

ceased once the sediments were isolated from the overlying 

water column, possibly because of the refractory nature of 

terrestrial organic matter. In the upper water column, seawater circulation continued to provide fluxes of paniculate 

organic matter and metals to the sediment; however, metals 

in the bottom brine were quickly depleted due to restricted 

circulation in the brine. Most of the chromium and nickel 

were retained in the anoxic sediment where organic-matter 

degradation was inhibited. The high potassium feldspar 

and low plagioclase contents in shale of group 1 relative to 

other shale may reflect the alteration of plagioclase to authigenic potassium feldspar, which has been described in the 

shale (D. Tromp and G. Whitney, 1992, unpub. data). High 

potassium concentrations enhance the alteration process 

and are a characteristic of brines derived from dissolution of 

the potassium-bearing evaporites or residual brines such as 

those in the Paradox Basin (Rice and others, 1994).

Shale group 2. As the basin filled, the pycnocline 

weakened and the brine mixed with seawater, becoming 

less saline throughout the basin and only mildly reducing. 

Argillaceous shale accumulated in the basin center, 

whereas calcareous shale formed nearer to and on the 

shelf. Detrital sodium feldspar was stable in the more 

dilute bottom waters. Reworking of organic matter at the 

sediment-water interface was sufficient to release the 

phosphate needed to form apatite present in many samples 

of shale group 2 but not sufficient to destroy all the 

organic matter. Partial recycling of phosphate and other 

nutrients to the surface waters stimulated primary productivity. Chromium and nickel were supplied continually by 

good circulation of seawater throughout the entire water 

column. Chromium was preferentially retained in the sediment relative to nickel because once-reduced chromium is 

relatively immobile, even during reworking of organic 

matter in the sediment, whereas nickel may diffuse out of 

the sediment (Shaw and others, 1990). As circulation of 

bottom water increased, the redox front moved down into 

the sediments and sulfate reduction did not begin until the 

sediments were partially isolated from the infinite sulfate 

reservoir in the bottom waters. More pyrite formed in 

these sediments than during formation of shales of group 1 

because release of iron from diagenetic processes was now 

time correlative with H->S generation.
N28 EVOLUTION OF SEDIMENTARY BASINS PARADOX BASIN

O

CO 

CO 

UJ 

DC 

CD 

CO

ccILU 

CD

£

CO

SHELF BASIN CENTER

OXIC

HEM(

1

T

CHEMOCLINE

ANOXIC

O

CO 

CO 

LU 

CC 

CD 

CO

ccILJL

O 

c\j 

LU 

CD 

<

CO

OXIC t

ANOXIC

Figure 16. Conditions during deposition of shales of groups 1 and 2. See text for explanation of groups.
GEOCHEMISTRY OF TWO INTERBEDS, PENNSYLVANIAN PARADOX FORMATION, UTAH AND COLORADO N29

CONCLUSIONS

During the Pennsylvanian Period, 33 repetitive cycles 

of marine evaporite-carbonate-siliciclastic rocks were 

deposited in the Paradox Basin of Utah and Colorado. The 

similarity in the repetitive lithologic sequences of these 33 

cycles was controlled primarily by eustasy (transgressive 

and regressive events). The vertical and aerial variability 

within and between interbeds of cycles 3 and 5 suggests that 

somewhat unique physical and chemical conditions existed 

during deposition of each cycle.

1. Variability in the mineralogy of silicates across the 

basin suggests that, during cycle 5, clastic material 

was derived from separate source areas to the southwest, the east, and the north. Mineralogical uniformity of elastics in cycle 3 suggests either one source 

or effective mixing of multiple sources.

2. Hydrogen indices vary both across the basin and vertically in cores because of changes in the proportions of terrestrial- and algal-derived organic matter 

deposited and preserved and because of differential 

maturation of the organic matter across the basin.

3. Sulfur and iron geochemistry suggests that, at the 

onset of transgression, the water column became 

stratified, possibly because of salt dissolution, and 

anoxic conditions persisted at the sediment-water 

interface. As transgression proceeded, seawater circulation mixed the water column and anoxic conditions moved deeper into the sediment.

4. Trace-metal concentrations in carbonaceous rocks 

suggest that circulation was good throughout the 

basin and indicate that H2S was not an important 

component of water in the basin.

5. Shale in the interbeds was deposited under two sets 

of conditions. Shale of group 1 was not enriched in 

metals, contains terrestrially derived organic matter, 

and was deposited during early transgressive phases 

when circulation was restricted. Shale of group 2 

was enriched in chromium, nickel, and algal matter; 

was deposited when seawater circulated throughout 

the basin, and is the notable petroleum source rock 

in the basin.

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68, p. 574-597.

Emerson, S.R., and Huested, S.S., 1991, Ocean anoxia and the 

concentrations of molybdenum and vanadium in seawater: 

Marine Chemistry, v. 34, p. 177-196.

Engel, M.H., and Macko, S.A., eds., 1993, Organic Geochemistry Principles and Applications: New York, Plenum 

Press, 861 p.
N30 EVOLUTION OF SEDIMENTARY BASINS PARADOX BASIN

Goldhaber, M.B., and Kaplan, I.R., 1974, The sulfur cycle, in 

Goldberg, E.D., ed.. The Sea, Volume 5 Marine chemistry: 

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 1975, Controls and consequences of sulfate reduction rates 

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Hite, R.J., 1960, Stratigraphy of the saline facies of the Paradox 

Member of the Hermosa Formation of southeastern Utah and 

southwestern Colorado, in Geology of the Paradox Basin Fold 

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 1961, Potash-bearing evaporite cycles in the salt anticlines 

of the Paradox Basin, Colorado and Utah, in Short Papers in 

the Geologic and Hydrologic Sciences: U.S. Geological Survey Professional Paper 424-D, p. D135-D138.

 1968, Salt deposits of the Paradox deposits of the Paradox 

Basin (Utah), in Saline Deposits: Geological Society of 

America Special Paper 88, p. 319-330.

 1970, Shelf carbonate sedimentation controlled by salinity 

in the Paradox Basin, southeast Utah, in Rau, J.L., and Dellwig, L.F., eds., Third Symposium on Salt: Cleveland, Northern Ohio Geological Society, p. 48-66.

-1983, Preliminary mineralogical and geochemical data

from the D.O.E. Gibson Dome corehole No. 1, San Juan 

County, Utah: U.S. Geological Survey Open-File Report 

83-780, 57 p.

Hite, R.J., and Anders, D.E., 1991, Petroleum and Evaporites, in 

Melvin, J.L., ed., Evaporites, Petroleum, and Mineral 

Resources: Amsterdam, Elsevier, p. 349-411.

Hite, R.J., Anders, D.E., and Ging, T.G., 1984, Organic-rich 

source rocks of Pennsylvanian age in the Paradox Basin of 

Utah and Colorado, in Woodward, J., Meissner, F.F., and 

Clayton, J.L., eds., Hydrocarbon Source rocks of the greater 

Rocky Mountain region: Denver, Rocky Mountain Association of Geologists, p. 255-274.

Hite, R.J., and Buckner, D.H., 1981, Stratigraphic correlations, 

facies concepts, and cyclicity in Pennsylvanian rocks of the 

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Basin: Denver, Rocky Mountain Association of Geologists, p. 

147-159.

Holser, W.T., and Kaplan, I.R., 1966, Isotope geochemistry of sedimentary sulfates: Chemical Geology, v. 1, p. 93-135.

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rocks, San Juan Basin and adjacent areas, Utah, Colorado, Arizona, and New Mexico: U.S. Geological Survey Bulletin 

1808-0,44 p.

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34, p. 195-212.

Kendall, A.C., 1987, Depositional model for carbonate-evaporite 

cyclicity; Middle Pennsylvanian of Paradox Basin: American 

Association of Petroleum Geologists Bulletin, v. 71, p. 576.

Lewan, M.D., 1984, Factors controlling the proportionality of 

vanadium to nickel in crude oils: Geochimica et CosmochimicaActa, v. 49, p. 2231-2238.

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pyrite: Fortschritte der Mineralogie, v. 43, p. 273-309.

Mallory, W.W., 1975, Middle and southern Rocky Mountains, 

northern Colorado Plateau, and eastern Great Basin region, in 

Paleotectonic Investigations of the Pennsylvanian System in

the United States, Part I Introduction and Regional Analyses 

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availability of iron: American Journal of Science, v. 282, p. 

1244-1263.

Raup, O.B., and Hite R.J., 1992, Lithology of evaporite cycles and 

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Basin, Utah and Colorado: U.S. Geological Survey Bulletin 

2000-B, 37 p.

Reid, F.S., and Berghorn, C.E., 1981, Facies recognition and 

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111-117.

Rice, C.A., Breit, G.N., and Hills, F.A., 1994, Mg, Sr, and K abundances in sulfate and water soluble minerals from the Paradox 

Formation Depositional and diagenetic indicators: 1994 

Abstracts with Program, Geological Society of America Rocky 

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Saelen, G., Raiswell, R., Talbot, M.R., Skei, J.M., and Bottrell, 

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1090-1094.

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100°C: Geochimica et Cosmochimica Acta, v. 55, p. 

1495-1504.

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pull-apart basin of Pennsylvanian age, in Peterson, J.A., ed., 

Paleotectonics and Sedimentation in the Rocky Mountain 

Region, United States: American Association of Petroleum 

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Country: Four Corners Geological Society Field Conference, 

8th, Guidebook, p. 193-210.

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Cosmochimica Acta, v. 57, p. 3023-3039.

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253-272.

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in water and seawater: Deep-Sea Research, v. 17, p. 721-735.

Wengerd, S.A., 1962, Pennsylvanian sedimentation in Paradox 

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Association of Petroleum Geologists, p. 264-330.

Whelan, J.K., and Thompson-Rizer, C.L., 1993, Chemical methods for assessing kerogen and protokerogen types and maturity, in Engel, M.H., and Macko, S.A., eds., Organic 

Geochemistry Principles and Applications: New York, Plenum Press, p. 289-354.

Williams-Stroud, S., 1994, Solution to the Paradox? Results of 

some chemical equilibrium and mass balance calculations 

applied to the Paradox Basin evaporite deposit: American 

Journal of Science, v. 294, p. 1-39.

Published in the Central Region, Denver, Colorado 

Manuscript approved for publication November 21, 1995 

Edited by Richard W. Scott, Jr. 

Graphics prepared by Norma Macs;

use made of author-drafted material 

Photocomposition by Gayle M. Dumonceaux

APPENDIX 1 CORE DESCRIPTIONS AND SAMPLING

INFORMATION
N34 EVOLUTION OF SEDIMENTARY BASINS PARADOX BASIN

0

200

GAMMA RAY LOG 

(API units)

200

400

DEPTH CORE DESCRIPTION 

(meters)

 ouo 

810 BIO815

Q-l C

O I3 

820

825

820-

830

\

\ 825- 

835 \

\ft9Q_

~'' i ' i r~

1

1 1 1

1

1 1 1

1

1 1 1

1

1 1 1

1

 1 1

1

/' / /'

/,/ /,,

/ / /

III,

=*=

 

=^

=^=V-=:

 r ' ' '

1

1

Anhydrite 

Siltstone

Medium-gray 

limestone

Dark-gray to black 

shaly to silty 

dolostone

Dark-gray to grayblack shale

Medium- to darkgray siltstone

Limestone

 Sample

U.S. Department of Energy Elk Ridge No. 1, sec. 30, T. 37 S., 

R. 13 E., San Juan County, Utah. API 4303790625. Cycle 5.

Twenty-one meters of cycle 5 was examined and sampled. The 

lower portion of the sampled interval is 3 m of limestone, 

overlain by 1.5 m medium- to dark-gray siltstone and 8 m of 

dark-gray to gray-black shale. The shale is laminated and 

contains abundant reddish organic matter, silt-size quartz and 

dolomite, well-oriented muscovite, and large pyrite grains

elongated along laminae. Above the shale are 1.5 m of dark-gray 

to black dolostone, almost 5 m of gray limestone, 1.5 m of 

siltstone, and 1.5 m of anhydrite at the top of the interval. The 

dolostone is silty and weakly laminated and contains dolomite 

rhombs in a clay-carbonate matrix. Some shell fragments and 

possible echinoderm tests have been replaced by chalcedony and 

(or) micritic calcite. Pyrite is present as euhedral cubes, 

disseminated anhedral grains, and cement.
GEOCHEMISTRY OF TWO INTERBEDS, PENNSYLVANIAN PARADOX FORMATION, UTAH AND COLORADO N35

GAMMA RAY LOG DEPTH CORE DESCRIPTION

0 (API units) 20° (meters)

200 400

773

Silty limestone

Calcareous 

siltstone

3 Shaly limestone

Massive darkbrown shale and 

shaly limestone

Silty limestone

Shaly to silty 

dolostone

- 800 Sample

U.S. Department of Energy Elk Ridge No. 1, sec. 30, T. 37 S., 

R. 13 E., San Juan County, Utah. API 4303790625. Cycle 3.

Approximately 24 m of cycle 3 was examined and sampled in 

this core. The lower part of the sampled interval is represented 

by shaly to silty, laminated dolostone. In some areas, the 

laminae are disrupted as if bioturbated. One area rich in organic 

matter contains a vein of pyrite cement. The dolostone contains 

minor to trace glauconite, anhydrite, and muscovite. About 16m 

of alternating silty to shaly limestone and massive dark-brown

calcareous shale beds overlies the dolostone. The shale contains 

some fine-sand-size quartz and carbonate grains, well-oriented 

muscovite grains, micritic carbonates, disseminated anhedral 

pyrite, and minor pyrite cement. The silty limestone has 

disrupted laminae, sparry calcite replacing shell fragments, and 

fine-sand-size quartz. Pyrite is present as anhedral grains and 

ragged-appearing framboids and framboid aggregates. A 

calcareous siltstone (2.5 m thick) overlies the alternating bed 

interval and is overlain by more silty limestone.
N36 EVOLUTION OF SEDIMENTARY BASINS PARADOX BASIN

0

GAMMA RAY LOG 

(API units)

DEPTH CORE DESCRIPTION 

200 (meters)

- 1,725

- 1,730

1,735-p

- 1,745

- 1,750

Shaly crinoidal 

limestone

Shelly limestone

Gradational contact 

Platy to massive

black shale 

Shaly dolostone

Finely laminated 

black shale

Platy black shale

 Sample

Carbonit Exploration State No. 1-16, SE%NW% sec. 16, T. 39 

S., R. 21 E., San Juan County, Utah. API 4303730603. Cycle

5. Approximately 6 m of cycle 5 core was examined and 

sampled. A platy, dark-gray to black shale in the lower 3.4 m of 

the interval grades upward into a massive, medium-gray, 

fossiliferous limestone. The shale appears to be less organic rich 

upward. Detrital grains in the shale are mostly silt-size quartz

and calcite. Shell fragments are rare to common. Dolomite 

rhombs are the major authigenic component and can make up a 

major part of the shale. Pyrite is abundant as framboids and 

shell replacement. Some larger (silt-size) euhedral crystals of 

pyrite were observed in one sample (a dolomitic shale, 1,738.6 

m). Marcasite may also be present.
GEOCHEMISTRY OF TWO INTERBEDS, PENNSYLVANIAN PARADOX FORMATION, UTAH AND COLORADO N37

GAMMA RAY LOG 

0 (API units)

DEPTH CORE DESCRIPTION 

200 (meters)

"" 1,681

1,680

1,685

1,690 1,685-

- 1,695

- 1,700

1,705

- 1,710

- 1,715

1,690-1

1,692-

Massive limestone

Porous limestone

Massive, crinoidal 

limestone

Massive to platy 

black shale

Sample

Carbonit Exploration State No. 1-16, SEV&NW% sec. 16, T. 39 

S., R. 21 E., San Juan County, Utah. API 4303730603. Cycle

3. During cycle 3 time, the location of this well was on or close 

to a shallow marine shelf that bounded the western margin of the 

basin (text fig. 4B). The interval examined is approximately 

10.7 m thick and contains, in ascending order, a massive to platy, 

dark-gray to black shale in the lowest part (4.9 m thick); a 

massive, medium-gray, crinoidal limestone (2 m thick); a vuggy, 

light-gray, fossiliferous limestone (3 m thick); and a massive, 

light-gray, crinoidal limestone at the top. The lowermost dark

shale contains common to abundant, silt-size quartz, feldspar, 

and muscovite. Some shell fragments, and lenticular 

concentrations of sponge spicules as long as a few millimeters, 

are present. Authigenic minerals include sparse patches of 

microcrystalline calcite cement; common, well-developed, siltsize dolomite rhombs; abundant pyrite; and possibly some 

marcasite. The pyrite is present mostly as small (silt-size), 

disseminated crystals; however, larger (silt-size), anhedral, 

"hairy" crystals are common. Only a few framboids and pyrite 

replacements of shell fragments were observed.
N38 EVOLUTION OF SEDIMENTARY BASINS PARADOX BASIN

0

GAMMA RAY LOG DEPTH CORE DESCRIPTION 

(API units) ____200 (meters)

_ -\ o -\ c . _ _ . Massive black 

shale

- 1915

- 1,920

1,925

1)925_

- 1,935

- 1,940

1,927-

Fractures or 

veins

Massive black 

shale

Sample

Southland Royalty West Water Creek No. 1, SWViSEVi sec. 4, 

T. 38 S., R. 22 E., San Juan County, Utah. API 4303730713. 

Cycle 3. Cycle 3 in this core is approximately 6 m thick and is 

predominantly a massive to platy, dark-gray to black shale. 

Within the upper 2 m, massive fractures or veins are filled with 

sulfides and sulfate minerals. The shale is more organic rich in 

its upper part, and both organic matter and the amount of clastic 

detritus increase upward. The uppermost sample contains 

abundant, silt-size quartz, feldspar, and muscovite, whereas the 

lowermost sample contains only rare silt-size quartz and 

muscovite grains. In all of the samples, carbonate grains

(possibly abraded shell fragments), shell fragments, and sponge 

spicules were common. Some lenticular concentrations of 

sponge spicules are observed. Among the authigenic minerals 

are sparse to common, well-developed, occasionally zoned 

dolomite rhombs; pyrite; and, in the uppermost sample, 

chalcedony (partially replacing shell fragments) and patches of 

microcrystalline calcite cement in the spicule-rich lenses. Pyrite 

is common and is present mostly as framboids and disseminated, 

silt-size crystals. The framboids are most common in the lower 

part of the sampled interval, hi the lower part, pyrite partially 

replaces sponge spicules and shell fragments.
GEOCHEMISTRY OF TWO INTERBEDS, PENNSYLVANIAN PARADOX FORMATION, UTAH AND COLORADO N39

GAMMA RAY LOG DEPTH CORE DESCRIPTION 

0 (API units) 200 (meters)

1,942 -

1,945

1,949

I I I

Crinoidal and shelly 

limestone

Gradational contact

Massive black shale

Sample

E.L. and B.R. Cox Aztec Federal No. 1, sec. 24, T. 37 S., R. 

23 E., San Juan County, Utah. API 4303730724. Cycle 5.

Approximately 6.3 m of core was sampled and examined. The 

lower 4.5 m is a massive, dark-gray to black, very organic rich 

shale that grades upward into a massive, medium-gray, 

fossiliferous, limestone. In the shale, silt-size quartz and

muscovite grains are rare to common and decrease upward in 

amount. Unlike the dolostone, no shell fragments are observed 

in the shale. Pyrite was the only observed authigenic mineral. 

Pyrite is common to abundant and is present mostly as dispersed, 

single, silt-size crystals. A few framboids are present, and some 

may be overgrown or infilled.
N40 EVOLUTION OF SEDIMENTARY BASINS PARADOX BASIN

0

GAMMA RAY LOG 

(API units)

DEPTH CORE DESCRIPTION 

200 (meters)

- 1.715/

- 1,720

1,725

,1,719 

1,720-

No gamma ray tool response

- 1,740

1,725

1,729

Crinoidal limestone 

Gradational contact 

Fractures or 

veins

Massive to platy 

black shale

Siltstone and 

sandstone

 Sample

McCulloch Oil and Gas Corp. Pickett Federal No. 1-33, 

SEV4NEV4SWV4 sec. 33, T. 36 S., R. 25 E., San Juan County, 

Utah. API 43037330539. Cycle 5. Of the 9.5 m of core 

examined, the lower 3 m is sandstone and siltstone. These are 

overlain by platy to massive, dark-gray to black, fossiliferous, 

organic-rich shale approximately 3 m thick. This shale grades 

upward into a dark gray to black shale that is very organic-rich 

and devoid of fossils. This upper shale is approximately 3.5 m 

thick and grades upward into a massive, medium-gray, 

fossiliferous (crinoidal) limestone. Sulfate- or carbonate-filled 

fractures or veins are present in the shale close to the limestone 

contact. The sandstone (and siltstone) is generally silt size to 

very fine grained, sublitharenite to quartzarenite. Clay matrix 

content ranges from trace to common and probably decreases

upward. The sandstone is almost completely cemented by porefilling calcite and, in some samples, dolomite. The lower shale 

interval contains abundant silt-size quartz and muscovite, shell 

fragments, deformed phosphatic(?) pelloids, and elongate 

agglomerates. The amount of shell fragments and pelloids 

appears to decrease upward. The upper shale is very similar to 

the lower shale, except, as mentioned before, it is more organicrich and is devoid of fossils, hi both the upper and lower shale 

intervals, dolomite and pyrite are the major authigenic minerals. 

Dolomite is generally present as silt-size rhombs. Pyrite is 

present as framboids or single crystals. The framboids are 

sometimes clustered, hi the lowermost shale interval, some shell 

fragments are replaced by pyrite.
GEOCHEMISTRY OF TWO INTERBEDS, PENNSYLVANIAN PARADOX FORMATION, UTAH AND COLORADO N41

0

200

GAMMA RAY LOG 20Q DEPTH CORE DESCRIPTION

(API units) 400

(meters)

1,751

1,755-1

- 1,770

1,760-

Crinoidal limestone

Massive to platy 

black shale

Carbonate and 

sulfide "stars"

Massive black 

shale

 Sample

Santa Fe Energy Lake Canyon Prospect Federal No. 1-27, 

NW^NW^ sec. 27, T. 36 S., R. 25 E., San Juan County, 

Utah. API 4303730692. Cycle 3. Approximately 9 m of this 

core was examined and sampled. The lower 8 m is a massive, 

dark-gray to black, organic-rich shale and is capped by a 

massive, medium-gray, crinoidal limestone, hi roughly the 

center of the shale interval are "star-shaped" sulfate-sulfide 

nodules and possibly some halite crystals. Silt-size quartz, 

muscovite, and carbonate grains are common to abundant in all 

the shale samples. Some shell fragments are present in the 

lowermost sample. Elongate patches (approximately 0.1 mm 

long) of agglomerated carbonate and silica grains, some hollow,

are present in the shale and are most abundant in the uppermost 

shale sample. The agglomerates are assumed to have biological 

affinities and may be either compacted tests of agglutinated 

foraminifera or algal spore cases. The major authigenic minerals 

are silt-size dolomite rhombs (only in the upper part of the 

shale), calcite, and pyrite. Pyrite is common to abundant and is 

present mostly as dispersed single crystals in the upper part of 

the shale and framboids in the lower part. Within the sulfatesulfide nodular interval, large patches of calcite laths are present. 

These laths commonly contain anhydrite, large euhedral pyrite 

crystals, and chalcedony, hi addition, layers of microcrystalline 

calcite-cemented shale are present in the nodular interval.
N42 EVOLUTION OF SEDIMENTARY BASINS PARADOX BASIN

0

GAMMA RAY LOG 

(API units)

DEPTH 

200 (meters)

CORE DESCRIPTION

1,939- 

1,940'

1,940

- 1,945---l ,944

III

I I

III

I I

III

Dolostone and 

shaly dolostone with 

nodules and fractures 

or veins filled with 

sulfate and silica 

Gradational contact

Massive to platy black 

shale with nodules and 

fractures or veins filled 

with pyrite, sulfate, 

and silica

Massive to platy black 

shale

Sample

Davis Oil Company Duncan Tevault No. 1, SWASEYt sec. 35, 

T. 40 N., R. 20 W., Dolores County, Colorado. API 

0503306047. Cycle 5. Approximately 2.7 m of this core was 

examined and sampled. The lower 1.8 m is a massive to platy, 

organic-rich, dark-gray to black shale. This shale grades upward 

into a dolomitic shale or clay-rich dolostone. The organic-rich 

shale contains common silt-size quartz, carbonate, and muscovite 

grains, and elongate phosphatic(?) agglomerates. Pyrite, mostly 

as single crystals and framboids, is common in the dolostone and 

shale. Framboids are sometimes clustered, and their abundance

appears to decrease upward. Both the dolostone and shale 

contain fractures or veins filled with chalcedony, pyrite, and 

anhydrite and sparsely distributed calcite and sphalerite. 

Generally, these fractures or veins are zoned as host, euhedral 

pyrite crystals, euhedral sphalerite crystals and (or) calcite, 

anhydrite, and chalcedony, hi one sample (1,940-m depth), the 

chalcedony may have undergone repeated fracturing and filling. 

Some euhedral marcasite crystals were observed near or in these 

veins.
GEOCHEMISTRY OF TWO INTERBEDS, PENNSYLVANIAN PARADOX FORMATION, UTAH AND COLORADO N43

0

200

GAMMA RAY LOG 

(API units)

DEPTH CORE DESCRIPTION

200 (meters) 

400

- 870

gamma ray log proprietary 

and unavailable for publication

Delhi-Taylor Oil Co. Shafer No. 1, sec. 15, T. 26 S., R. 20 

E., Grand County, Utah. Cycle 5. This is the northernmost 

well sampled. Approximately 28 m of this core was 

examined and sampled. The lower 1 m is gray, laminated 

anhydrite. Above the anhydrite is black to brown shale. The 

black shale is overlain by about 5 m of gray to buff dolostone 

that has organic matter disseminated throughout. The 

dolomite is uniform anhedral grains, and some pyrite is 

present as anhedral grains. Above the dolostone is about 6 m 

of nodular anhydrite, overlain by 6 m of light-brown silty 

dolomite, about 2.5 m of buff to black dolomitic shale 

containing numerous halite veins, 3 m of light-brown 

dolomite with some halite veins, and a bed of gray anhydrite 

at the top of the interval.

875

880

880

885

890

885-

890-

895

900

895-

- 905

 Sample

900'

903'

II

III

II

III

1 1

I 1 1

III

II

1 1 I

II

1 1 1

II

1 1 1

II

1 1 I

II

1 I 1

1 1

III

ll

I 1 1

ll

III

1 1

III

1 1

III

ll

III

1 1

Anhydrite 

Shaly dolostone

Black shale

Silty to shaly 

dolostone

Anhydrite with 

some shaly 

laminations

Silty to shaly 

dolostone

Thinly bedded, 

black to brown 

shale

Anhydrite
N44 EVOLUTION OF SEDIMENTARY BASINS PARADOX BASIN

0

200

GAMMA RAY LOG 

(API units)

DEPTH 

200 (meters) 

400

CORE DESCRIPTION

- 755

Gamma ray log proprietary 

and unavailable for publication

- 76(

765

770

775

780

/ U*J 

/

770-

775-

780-

785-

/ B/ /

//I i / 1 1 / / 1 i / /

i 1 1 / /

/

/i/ ^

, / i i

i i

M /

/ /

/ , 1 /

t

/ ,

i \i

i

i

i

i

 iI

^miA ~

^ .^. .'~^ 

L-rlAi i

_^_j 

^r

_1^^

Anhydrite 

Gradational contact

Shaly to silty 

dolostone

Sharp contact

Massive black shale 

and thin beds of 

shaly dolostone

Sharp contact 

Siltstone and 

sandstone 

Shaly to silty

dolostone 

Sandstone

 Sample

Delhi-Taylor Oil Co. Shafer No. 1, sec. 15, T. 26 S., R. 20 E., 

Grand County, Utah. Cycle 3. Approximately 32 m of this 

core was examined, and 33 samples were collected. It is the 

most sampled of all the wells. The deepest part of the interval 

contains a medium-gray anhydrite, above which is medium-gray 

to brown, sometimes dolomitic or calcareous, shale; siltstone; 

sandstone; and dolostone (total about 7.5 m thick). The siltstone 

and sandstone decrease upward. These medium-gray to brown 

beds grade upward into darker gray to black, organic-rich shale 

about 4.5 m thick. The shale is overlain by dolostone 2 m thick 

and the interval is capped by anhydrite. Fractures filled with 

anhydrite, pyrite, and halite are common throughout the interval 

but are most abundant in the upper shale and dolostone. 

Generally, both the medium-gray to brown shale and the darkgray to black shale contain common to abundant, silt-size quartz,

feldspar, and muscovite. Some foraminfera tests and elongate 

agglomerates of carbonate and silica grains are present in the 

upper, organic-rich shale. Sporadic patches of microcrystalline 

calcite are present. Dolomite rhombs were observed only in the 

uppermost shale, hi one sample (775.3 m), a veinlet of 

individual and coalesced sphalerite crystals was observed, as 

well as calcium phosphate-rich patches. Pyrite is rare to 

abundant in the interval and is present mostly as single, 

dispersed, silt-size crystals or as framboids. Some possible 

euhedral to subhedral marcasite is present. The black shale and 

shaly dolostone contain veins of halite, one of which (771.5 m) 

was examined in thin section. The vein contains chalcedony, 

dolomite, halite, and iron sulfide minerals. The iron sulfides are 

very fine grained to coarse-grained anhedral grains, some of 

which may be marcasite
GEOCHEMISTRY OF TWO INTERBEDS, PENNSYLVANIAN PARADOX FORMATION, UTAH AND COLORADO N45

0

GAMMA RAY LOG 

(API units)

200

DEPTH CORE DESCRIPTION 

(meters)

933

- 925

935-

- 930

/

/ 

935

940

945

^^

- 950

940-

945-

,949

ill

I T

III

I I

I I I

/TIII

_L_/

1 i r

Dolostone 

Anhydrite

Dolostone and 

shaly dolostone

Brownish-black 

dolomitic siltstone 

and sandstone

Anhydrite

Brownish-black 

limestone

Laminated brown 

shale

Sample

U.S. Department of Energy Gibson Dome No. 1, sec. 21, T. 30 

S., R. 21 E., San Juan County, Utah. Cycle 5. Approximately 

16m was examined and sampled in this core. The lowest part of 

the interval is about 1.5 m of laminated brown shale, the upper 

part of which contains more silt and is grayer. Anhydrite, siltsize carbonates, and disseminated anhedral pyrite grains are 

present in minor or trace amounts. The shale is overlain by 3.5 

m of brownish-black limestone, 0.4 m of anhydrite, and some 5

m of brownish-black dolomitic siltstone and sandstone. The 

siltstone is quite porous. The dolomite is mostly rounded grains, 

but some rhombs are present; minor amounts of muscovite, 

biotite, anhydrite, and potassium feldspar were observed in thin 

section. Approximately 6 m of dolostone to shaly dolostone 

overlies the siltstone. The dolostone unit contains a small bed of 

anhydrite.
N46 EVOLUTION OF SEDIMENTARY BASINS PARADOX BASIN

0

GAMMA RAY LOG 

(API units) 200

DEPTH CORE DESCRIPTION 

(meters)

867

- 865 Anhydrite

Silty dolostone

Gray to black 

silty shale and 

claystone

- 895

Siltstone

Anhydrite

Sample

U.S. Department of Energy Gibson Dome No. 1, sec. 21, T. 30 

S., R. 21 E., San Juan County, Utah. Cycle 3. Approximately 

24 m was examined and sampled. The lowest part of the 

sampled interval is anhydrite overlain by 2 m of siltstone. The 

siltstone contains very abundant shell fragments. Pyrite is 

present as small anhedral grains and infilled framboids. The

siltstone is overlain by 9.5 m of gray to black silty shale and 

claystone. This unit is calcareous, and thin dolomite beds are 

present throughout. The shale contains variable amounts of shell 

fragments, micritic calcite, well-oriented muscovite, and 

abundant pyrite framboids. Above the shale is about 6 m of silty 

dolostone overlain by anhydrite.
GEOCHEMISTRY OF TWO INTERBEDS, PENNSYLVANIAN PARADOX FORMATION, UTAH AND COLORADO N47

DEPTH CORE DESCRIPTION 0

200

GAMMA RAY LOG 

(API units)

200

400

(meters)

- 1,790 ,1,798

- 1,795

1,800

- 1,810 L803

Limestone 

Gradational contact

Vertical fracture or 

vein (1,800.5- 

1,800.75)

Massive to platy 

black shale

Vertical fracture or 

vein (1,802.25- 

1,802.9)

Sample

Transco Exploration TXPOC Crowley Ranch No. 1-25, sec. 

25, T. 34 S., R. 25 E., San Juan County, Utah. API

4303730978. Cycle 5. Out of the approximately 5 m of core 

examined and sampled, the lower 3.7 m is a dark-gray to black, 

organic-rich shale. The shale grades upward into a limestone or 

dolostone that makes up the remainder of the core. Two 

prominent veins filled with anhydrite and calcite are present 

within the shale. One of the veins (1,802.8 m), examined in thin

section, is filled with calcite. Incorporated within the calcite are 

large crystals of anhydrite and pyrite, and inclusions of the host 

rock. Pyrite crystals generally line the vein. The shale contains 

sparse silt-size quartz and muscovite grains, rare shell fragments, 

and, in the lowermost sample (1,802.8 m), abundant elongate 

agglomerates of calcite or silica. Dolomite rhombs are common 

in the upper sample. Pyrite is common and present as framboids 

and single crystals.
N48 EVOLUTION OF SEDIMENTARY BASINS PARADOX BASIN

0

GAMMA RAY LOG 

(API units) 200

DEPTH 

(meters)

- 1,84

McCulloch Oil and Gas Corp. Norton Federal No. 

1-4, NE1/4SE%NE1/4 sec. 4, T. 38 N., R. 18 W., 

Montezuma County, Colorado. API 0508306260. 

Cycle 5. Approximately 11 m was examined and 

sampled in this core. The lower 1.2 m is anhydrite and 

dolostone. The dolomite in the dolostone is finely 

crystalline, and all of the intercrystalline porosity is 

filled with anhydrite and gypsum. The dolostone 

grades upward into anhydrite. Both the dolostone and 

anhydrite contain sparse, very fine grained, well-sorted 

quartz and muscovite grains. Above the anhydrite is a 

silty to very fine grained sublitharenite. This clastic 

bed has a sparse clay-rich matrix and patchy calcite 

cement. Anhydrite veins vertically cut across this bed. 

The siltstone and sandstone grade upward into a platy, 

dark-gray to black, very organic rich shale about 0.6 m 

thick. This darker shale grades into a massive, darkgray shale 5.8m thick that, in turn, grades upward into 

a light-gray, vuggy dolostone. Both the darker and 

relatively lighter shale contain common silt-size quartz 

and muscovite grains. The darker shale contains 

elongate agglomerates of calcite or silica. The lighter 

shale contains dolomite rhombs and sparse patches of 

microcrystalline carbonate cement (calcite?). Pyrite is 

common in both types of shale and is present as single 

crystals and framboids. The framboids are more 

common in the darker, organic-rich shale. The 

dolostone is a mosaic of interlocking crystals and has 

abundant intercrystalline porosity and vugs. Many 

pores and vugs are filled with pyrobitumen ("dead oil") 

or anhydrite. The pyrobitumen probably migrated into 

the rock after anhydrite cementation.

CORE DESCRIPTION

1,842

1,845

1,850

\ 

- 1,855

1,845

1,850

1,853

^H

^"

/'T /'

/ / /

III

' / /

/ 7 /

i / I

1 I 1

i I 1

__/ U . /

 ^-^-^ H

:: s^irz]

 : = ^ L ' '_

~-~ , ' -^~*~. 

11 »~

>^=

 

^*=

IS

/ / / ,

/ 1 /

1 / / ,

Dolostone with 

dead oil

Gradational

UUI lldl/l

Fractures or 

veins

Dolomitic siltstone

Fracture or 

vein

Platy black shale

Siltstone and 

sandstone

Anhydrite 

Dnlnstone

 Sample
GEOCHEMISTRY OF TWO INTERBEDS, PENNSYLVANIAN PARADOX FORMATION, UTAH AND COLORADO N49

GAMMA RAY LOG 

0 (API units)

DEPTH CORE DESCRIPTION 

200 (meters)

1,804-r

- 1,795

- 1,800

1,805-

1,805

1,807'

Shaly limestone

Massive black shale

- 1,810 Sample

- 1,815

- 1,820

- 1825

- 1830

McCulloch Oil and Gas Corp. Norton Federal No. 1-4, 

NE^SE'^NE1^ sec. 4, T. 38 N., R. 18 W., Montezuma County, 

Colorado. API 0508306260. Cycle 3. Only about 3.6 m was 

examined and sampled. The cored interval is represented by a 

massive, dark-gray to black, organic-rich shale that contains 

common silt-size quartz and muscovite. The uppermost sample 

(1,804 m) is calcareous and contains sparse shell fragments.

Well-developed zoned dolomite rhombs are present in many of 

the samples. The lowermost sample contains patches of 

microcrystalline calcite. Pyrite is common to abundant and is 

present as disseminated, silt-size crystals and as framboids. 

Shell fragments partially replaced by pyrite are present in the 

uppermost sample. Some anhedral to subhedral marcasite is 

present in many of the samples.
N50 EVOLUTION OF SEDIMENTARY BASINS PARADOX BASIN

0

GAMMA RAY LOG 

(API units)

DEPTH 

200 (meters)

CORE DESCRIPTION

1,802-

- 1,795

- 1,800

1,805 1,805-

- 1,810

1,808-

Fracture or vein 

Massive black shale 

Shaly limestone 

Fractures or veins

filled with pyrite

Massive to platy 

black shale

Limestone 

Crosslaminated, 

light- to mediumgray siltstone 

and sandstone 

(some convolute 

bedding)

Light- to mediumgray shaly limestone

Bedded, lightgray limestone

Sample

Celsius Energy Woods Unit No. 1-S, NW^SEVSNW^ sec. 20, 

T. 37 N., R 18 W., Montezuma County, Colorado. 

API508306359. Cycle 5. Approximately 6 m was examined 

and-sampled. The lowest 0.6 m is a light-gray limestone. 

Sharply overlying the limestone is 7 m of light- to medium-gray 

shale intercalated with dark-gray shale. The shale grades 

upward into 2.8 m of laminated and ripple-cross-laminated 

siltstone and sandstone. Some convolute bedding is observed. 

The siltstone and sandstone grade upward into a thin limestone, 

that is overlain by a dark-gray to black, organic-rich shale. Some 

veinlets filled with pyrite, calcite, and chalcedony are present 

near the top of the core (1,802-1,803 m). The intercalated light 

and dark shale exhibits organic-rich and organic-poor laminae 

and cross laminae and contains common silt-size quartz, 

muscovite, and calcite grains. A few pyritized foraminifera tests 

were observed. Pyrite is common as single crystals and infilled

framboids. The siltstone and sandstone are a sublitharenite or 

subarkose. Coarser grained intervals are generally cemented 

with patchy or micritic calcite cement and zoned dolomite 

rhombs. Finer grained intervals are clay and mica rich. Pyrite is 

present as crystals or infilled framboids. The overlying organicrich shale generally contains common silt-size quartz, muscovite, 

and calcite grains, and the amount of siliciclastics inceases 

upward. hi addition, this shale contains abundant shell 

fragments, rare to abundant dolomite rhombs (many zoned), and 

some elongate agglomerates, hi one sample (1,802.4 m), some 

pelloids (possibly phosphatic) are present. Pyrite is common as 

framboids, single grains, and shell replacement. hi the 

uppermost sample (1,802.4 m), one of the veinlets showed 

zonation similar to that observed in other wells; that is, host 

rock, pyrite, calcite, and chalcedony. Pyrite is present as 

relatively large euhedral crystals within the vein.
GEOCHEMISTRY OF TWO INTERBEDS, PENNSYLVANIAN PARADOX FORMATION, UTAH AND COLORADO N51

GAMMA RAY LOG DEPTH 

0 (API units) 20Q (meters)

- 2,540

- 2,645 Cycles

CORE DESCRIPTION

Vertical fractures or 

veins, some brecciated 

Massive black shale 

Shelly

Very shelly, dark gray 

to black shaly limestone 

Gradational contact 

Shell content decreases 

downward

Massive black shale

- 2,685

Sample

See caption for above figure on following page.
N52 EVOLUTION OF SEDIMENTARY BASINS PARADOX BASIN

Houston Oil and Mineral Corp. Ute Mountain No. 44-34, 

SE%SEi/4 sec. 24, T. 34 N., R. 14 W., Montezuma County, 

Colorado. API 508306172. Cycle 3 (preceding page). This is 

the southernmost well sampled. Only 23 m was available for 

examination and sampling. No core material was retrieved from 

2,674.3-m to 2,854.5-m depth. Below 2,854.5 m are anhydrite 

and dolostone that are not discussed herein because they may 

belong to cycle 4. The upper 21.5 m (above 2,674.3 m) is 

predominantly a massive, dark-gray to black shale. The shale is 

fossiliferous (shell fragments and sponge spicules) near the top, 

but the fossil abundance decreases with depth. No shell 

fragments were observed below 10 m from the top of the core.

Near the top of the sampled interval, vertical veins of anhydrite, 

pyrite, calcite, and (or) chalcedony, and brecciated shale are 

present. The shale is organic poor in the upper part of the 

interval but becomes more organic rich with depth. Silt-size 

quartz, calcite, and muscovite grains are generally common to 

abundant throughout. However, in the uppermost sample, clastic 

detritus is rare. The large amount of quartz indicated by XRD 

(appendix 2) may be due to siliceous sponge spicules. Dolomite 

rhombs, some zoned, are present in the upper samples but 

become sparse with depth. Pyrite is generally sparse in the shale 

and is present as disseminated silt-size crystals.
APPENDIX 2 LITHOLOGIC, CHEMICAL, ISOTOPIC, AND 

MINERALOGIC DATA FOR CORE SAMPLES IN STUDY
Appendix 2, table 1. Lithologic, chemical, isotopic, and mineralogic data for core samples in study.

[Lithology of samples is from core descriptions and rock type is the classification used in this Bulletin in most cases they are the same. SQJ, disulfide sulfur; Sgo f sul

sulfur; Ccor carbonate carbon; Corg, organic carbon; Ferct, reactive iron. Rock Eval data: S\, volatile hydrocarbons (in mg/g of rock); S2, generated hydrocarbons 

mg/g of rock); Tmax in °C (see text for description); HI, hydrogen index, and OI, oxygen index (see text for description). Isotope data are in per mil relative to Canon D

pyritization (see text for explanation). Mineralogical data for quartz, potassium feldspar, sodium feldspar, apatite, calcite, dolomite, anhydrite, halite, pyrite, and total 

inch. Inductively coupled plasma spectral data: major elements (Al, Ca, Fe, K, Mg, Na, P, Ti) are reported in weight percent; minor and trace elements are report

enriched concentrations as calculated using formulas shown in the text, na, data not available; insuf, insufficient data; sh., shale; siltst., siltstone; sandst, sandstone. <, b

Well name

Aztec Federal No. 1

Aztec Federal No. 1

Aztec Federal No. 1

Aztec Federal No. 1

Aztec Federal No. 1

Aztec Federal No. 1

Crowley Ranch No. 1-25

Crowley Ranch No. 1-25

Duncan Tevault No. 1

Duncan Tevault No. 1

Duncan Tevault No. 1

Duncan Tevault No. 1

Elk Ridge No. 1

Elk Ridge No. 1

Elk Ridge No. 1

Elk Ridge No. 1

Elk Ridge No. 1

Elk Ridge No. 1

Elk Ridge No. 1

Elk Ridge No. 1

Elk Ridge No. 1

Elk Ridge No. 1

Elk Ridge No. 1

Elk Ridge No. 1

Elk Ridge No. 1

Elk Ridge No. 1

Elk Ridge No. 1

Gibson Dome No. 1

Gibson Dome No. 1

Gibson Dome No. 1

Gibson Dome No. 1

Gibson Dome No. 1

Gibson Dome No. 1

Gibson Dome No. 1

Depth 

(ft)

6374.8

6378.5

6379.8

6384.3

6389.5

6393.3

5905.0

5915.0

6365.0

6367.0

6370.5

6371.0

2548.4

2560.4

2570.5

2578.5

2588.5

2594.7

2614.4

2653.6

2676.8

2680.7

2687.9

2693.8

2701.0

2706.7

2711.1

2846.6

2869.0

2873.0

2879.0

2885.6

2888.5

2890.5

Depth 

(m)

1943.0

1944.2

1944.6

1945.9

1947.5

1948.7

1799.8

1802.9

1940.1

1940.7

1941.7

1941.9

776.8

780.4

783.5

785.9

789.0

790.9

796.9

808.8

815.9

817.1

819.3

821.1

823.3

825.0

826.3

867.6

874.5

875.7

877.5

879.5

880.4

881.0

Cycle

Cycle 5

Cycle 5

Cycle 5

Cycle 5

Cycle 5

Cycle 5

Cycle 5

Cycle 5

Cycle 5

Cycle 5

Cycle 5

Cycle 5

Cycle 3

Cycle 3

Cycle 3

Cycle 3

Cycle 3

Cycle 3

Cycle 3

Cycle 5

Cycle 5

Cycle 5

Cycle 5

Cycle 5

Cycle 5

Cycle 5

Cycle 5

Cycle 3

Cycle 3

Cycle 3

Cycle 3

Cycle 3

Cycle 3

Cycle 3

Lithology 

of sample

Limestone

Limestone

Calcareous sh.

Calcareous sh.

Calcareous sh.

Calcareous sh.

Calcareous sh.

Calcareous sh.

Dolostone

Shaly dolomite

Dolomitic sh.

Argillaceous sh.

Limestone

Calcareous sh.

Limestone

Calcareous sh.

Calcareous sh.

Calcareous sh.

Shaly dolomite

Anhydrite

Shaly dolomite

Calcareous sh.

Argillaceous sh.

Argillaceous sh.

Argillaceous sh.

Calcareous sh.

Calcareous siltst.

Anhydrite

Dolostone

Dolostone

Dolomitic sh.

Calcareous sh.

Calcareous sh.

.Calcareous sh.

Rock type 

for statistics

Limestone

Limestone

Calcareous sh.

Calcareous sh.

Calcareous sh.

Calcareous sh.

Calcareous sh.

Calcareous sh.

Dolostone

Dolostone

Dolomitic sh.

Argillaceous sh.

Limestone

Calcareous sh.

Limestone

Calcareous sh.

Calcareous sh.

Calcareous sh.

Dolostone

Anhydrite

Dolostone

Calcareous sh.

Argillaceous sh.

Argillaceous sh.

Argillaceous sh.

Calcareous sh.

Siltstone

Anhydrite

Dolostone

Dolostone

Dolomitic sh.

Calcareous sh.

Calcareous sh.

Calcareous sh.

(w
Appendix 2, table 1. Lithologic, chemical, isotopic, and mineralogic data for core samples in study Continued.

Well name

Gibson Dome No. 1

Gibson Dome No. 1

Gibson Dome No. 1

Gibson Dome No. 1

Gibson Dome No. 1

Gibson Dome No. 1

Gibson Dome No. 1

Gibson Dome No. 1

Gibson Dome No. 1

Gibson Dome No. 1

Gibson Dome No. 1

Gibson Dome No. 1

Gibson Dome No. 1

Gibson Dome No. 1

Gibson Dome No. 1

Gibson Dome No. 1

Gibson Dome No. 1

Gibson Dome No. 1

Gibson Dome No. 1

Honaker Trail outcrop

Lake Canyon No. 1-27

Lake Cany on No. 1-27

Lake Canyon No. 1-27

Lake Canyon No. 1-27

Lake Cany on No. 1-27

Lake Canyon No. 1-27

Lake Cany on No. 1-27

Lake Cany on No. 1-27

Lake Canyon No. 1-27

Norton Federal No. 1-4

Norton Federal No. 1-4

Norton Federal No. 1-4

Norton Federal No. 1-4

Norton Federal No. 1-4

Norton Federal No. 1-4

Norton Federal No. 1-4

Norton Federal No. 1-4

Norton Federal No. 1-4

Norton Federal No. 1-4

Norton Federal No. 1-4

Depth

(ft)

2892.0

2893.9

2895.9

2897.2

2898.6

2902.7

2904.6

2907.5

2908.3

2922.5

3066.9

3069.6

3079.2

3080.8

3089.0

3096.3

3098.2

3098.6

3110.2

0.0

5748.5

5749.0

5752.8

5756.5

5762.3

5764.5

5767.0

5770.3

5774.5

5919.8

5925.0

5929.0

5929.8

6042.0

6044.3

6052.3

6057.5

6060.3

6062.3

6066.0

Depth 

(m)

881.5

882.1

882.7

883.1

883.5

884.7

885.3

886.2

886.4

890.8

934.8

935.6

938.5

939.0

941.5

943.8

944.3

944.5

948.0

0.0

1752.1

1752.3

1753.5

1754.6

1756.3

1757.0

1757.8

1758.8

1760.1

1804.4

1805.9

1807.2

1807.4

1841.6

1842.3

1844.7

1846.3

1847.2

1847.8

1848.9

Cycle

Cycle 3

Cycle 3

Cycle 3

Cycle 3

Cycle 3

Cycle 3

Cycle 3

Cycle 3

Cycle 3

Cycle 3

Cycle 5

Cycle 5

Cycle 5

Cycle 5

Cycle 5

Cycle 5

Cycle 5

Cycle 5

Cycle 5

Cycle 5

Cycle 3

Cycle 3

Cycle 3

Cycle 3

Cycle 3

Cycle 3

Cycle 3

Cycle 3

Cycle 3

Cycle 3

Cycle 3

Cycle 3

Cycle 3

Cycle 5

Cycle 5

Cycle 5

Cycle 5

Cycle 5

Cycle 5

Cycle 5

Lithology 

of sample

Calcareous sh.

Dolomitic sh.

Calcareous sh.

Dolomitic sh.

Calcareous sh.

Calcareous sh.

Calcareous sh.

Calcareous siltst.

Calcareous siltst.

Anhydrite

Anhydrite

Dolostone

Shaly dolomite

Dolomitic siltst.

Dolomitic siltst.

Dolomitic siltst.

Dolomitic siltst.

Anhydrite

Argillaceous sh.

Calcareous sh.

Limestone

Argillaceous sh.

Calcareous sh.

Calcareous sh.

Limestone

Calcareous sh.

Calcareous sh.

Calcareous sh.

Argillaceous sh.

Limestone

Calcareous sh.

Calcareous sh.

Calcareous sh.

Dolostone

Dolostone

Dolomitic siltst.

Dolomitic sh.

Dolomitic sh.

Argillaceous sh.

Argillaceous sh.

Rock type 

for statistics

Calcareous sh.

Dolomitic sh.

Calcareous sh.

Dolomitic sh.

Calcareous sh.

Calcareous sh.

Calcareous sh.

Siltstone

Siltstone

Anhydrite

Anhydrite

Dolostone

Dolostone

Siltstone

Siltstone

Siltstone

Siltstone

Anhydrite

Argillaceous sh.

Calcareous sh.

Limestone

Argillaceous sh.

Calcareous sh.

Calcareous sh.

Limestone

Calcareous sh.

Calcareous sh.

Calcareous sh.

Argillaceous sh.

Limestone

Calcareous sh.

Calcareous sh.

Calcareous sh.

Dolostone

Dolostone

Siltstone

Dolomitic sh.

Dolomitic sh.

Argillaceous sh.

Argillaceous sh.

(w
Appendix 2, table 1. Lithologic, chemical, isotopic, and mineralogic data for core samples in study Continued.

Well name

Norton Federal No. 1-4

Norton Federal No. 1-4

Norton Federal No. 1-4

Norton Federal No. 1-4

Pickett Federal No. 1-33

Pickett Federal No. 1-33

Pickett Federal No. 1-33

Pickett Federal No. 1-33

Pickett Federal No. 1-33

Pickett Federal No. 1-33

Pickett Federal No. 1-33

Pickett Federal No. 1-33

Pickett Federal No. 1-33

Pickett Federal No. 1-33

Pickett Federal No. 1-33

Pickett Federal No. 1-33

Pickett Federal No. 1-33

Pickett Federal No. 1-33

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

Shafer No. 1

Depth 

(ft)

6067.8

6071.5

6074.5

6077.3

5642.0

5644.3

5645.8

5648.0

5649.0

5651.2

5653.3

5656.5

5659.0

5660.8

5664.0

5665.5

5665.8

5670.5

2514.5

2529.0

2535.0

2536.5

2537.0

2539.0

2540.0

2541.0

2542.8

2543.8

2545.0

2546.3

2547.3

2548.8

2550.5

2551.5

2552.8

2555.3

2556.5

2558.0

2559.5

2560.5

Depth 

(m)

1849.5

1850.6

1851.5

1852.4

1719.7

1720.4

1720.8

1721.5

1721.8

1722.5

1723.1

1724.1

1724.9

1725.4

1726.4

1726.8

1726.9

1728.4

766.4

770.8

772.7

773.1

773.3

773.9

774.2

774.5

775.0

775.4

775.7

776.1

776.4

776.9

777.4

777.7

778.1

778.9

779.2

779.7

780.1

780.4

Cycle

Cycle 5

Cycle 5

Cycle 5

Cycle 5

Cycle 5

Cycle 5

Cycle 5

Cycle 5

Cycle 5

Cycle 5

Cycle 5

Cycle 5

Cycle 5

Cycle 5

Cycle 5

Cycle 5

Cycle 5

Cycle 5

Cycle 3

Cycle 3

Cycle 3

Cycle 3

Cycle 3

Cycle 3

Cycle 3

Cycle 3

Cycle 3

Cycle 3

Cycle 3

Cycle 3

Cycle 3

Cycle 3

Cycle 3

Cycle 3

Cycle 3

Cycle 3

Cycle 3

Cycle 3

Cycle 3

Cycle 3

Lithology 

of sample

Argillaceous sh.

Siltstone

Anhydrite

Dolostone

Limestone

Calcareous sh.

Calcareous sh.

Calcareous sh.

Calcareous sh.

Calcareous sh.

Argillaceous sh.

Argillaceous sh.

Argillaceous sh.

Argillaceous sh.

Argillaceous sh.

Calcareous siltst.

Dolomitic siltst.

Calcareous siltst.

Anhydrite

Shaly dolomite

Shaly dolomite

Dolomite

Shaly dolomite

Argillaceous sh.

Argillaceous sh.

Argillaceous sh.

Argillaceous sh.

Argillaceous sh.

Argillaceous sh.

Dolomitic sh.

Argillaceous sh.

Argillaceous sh.

Argillaceous sh.

Shaly dolomite

Argillaceous sh.

Argillaceous sh.

Dolomitic sh.

Shaly dolomite

Dolomitic sh.

Shaly dolomite

Rock type 

for statistics

Argillaceous sh.

Siltstone

Anhydrite

Dolostone

Limestone

Calcareous sh.

Calcareous sh.

Calcareous sh.

Calcareous sh.

Calcareous sh.

Argillaceous sh.

Argillaceous sh.

Argillaceous sh.

Argillaceous sh.

Argillaceous sh.

Siltstone

Siltstone

Siltstone

Anhydrite

Dolostone

Dolostone

Dolostone

Dolostone

Argillaceous sh.

Argillaceous sh.

Argillaceous sh.

Argillaceous sh.

Argillaceous sh.

Argillaceous sh.

Dolomitic sh.

Argillaceous sh.

Argillaceous sh.

Argillaceous sh.

Dolostone

Argillaceous sh.

Argillaceous sh.

Dolomitic sh.

Dolostone

Dolomitic sh.

Dolomitic sh.

(w
GEOCHEMISTRY OF TWO INTERBEDS, PENNSYLVANIAN PARADOX FORMATION, UTAH AND COLORADO N57

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Appendix 2, table 2. Lithologic, chemical, isotopic, and mineralogic data for core samples in study Continued.

Well name

Norton Federal No. 1-4

Norton Federal No. 1-4

Norton Federal No. 1-4

Norton Federal No. 1-4

Norton Federal No. 1-4

Norton Federal No. 1-4

Norton Federal No. 1-4

Norton Federal No. 1-4

Norton Federal No. 1-4

Norton Federal No. 1-4

Pickett Federal No. 1-33

Pickett Federal No. 1-33

Pickett Federal No. 1-33

Pickett Federal No. 1-33

Pickett Federal No. 1-33

Pickett Federal No. 1-33

Pickett Federal No. 1-33

Pickett Federal No. 1-33

Pickett Federal No. 1-33

Pickett Federal No. 1-33

Pickett Federal No. 1-33

Pickett Federal No. 1-33

Pickett Federal No. 1-33

Pickett Federal No. 1-33

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

Shafer No. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

Depth 

(ft)

6044.3

6052.3

6057.5

6060.3

6062.3

6066.0

6067.8

6071.5

6074.5

6077.3

5642.0

5644.3

5645.8

5648.0

5649.0

5651.2

5653.3

5656.5

5659.0

5660.8

5664.0

5665.5

5665.8

5670.5

2514.5

2529.0

2535.0

2536.5

2537.0

2539.0

2540.0

2541.0

2542.8

2543.8

2545.0

2546.3

2547.3

2548.8

2550.5

2551.5

Sflrg 

(weight percent)

na

O.01

na

O.01

0.04

0.02

0.08

na

na

O.01

na

0.06

0.72

0.19

0.04

O.01

0.35

0.03

0.04

0.06

0.02

na

0.08

na

0.12

na

na

na

na

O.01

0.01

0.03

0.07

0.04

0.04

na

0.07

0.03

0.05

0.01

(weight percent)

0.93

0.56

1.1

0.78

1.2

1.1

1.1

1.3

19

2.4

0.36

1.5

1.7

1.7

1.8

1.8

2.1

2.1

1.9

1.9

1.6

0.74

1.6

1.2

20

0.26

0.34

0.32

0.48

1.5

2.2

1.4

1.5

1.2

1.6

1.1

1.4

2.1

1.7

0.58

CCO3 

(weight percent)

9.5

5.7

5.8

6.5

2.4

0.60

0.40

1.9

3.3

11

9.4

5.1

3.2

3.6

3.2

3.3

2.8

2.8

2.4

1.4

na

6.3

4.4

3.2

1.4

7.0

7.7

9.1

7.3

1.9

1.8

3.0

2.7

2.7

2.9

4.4

2.3

2.9

1.8

8.9

C0rg 

(weight percent)

0.30

0.37

0.80

0.47

2.7

2.2

3.1

0.20

0.25

0.23

0.19

2.7

2.0

2.9

2.4

2.6

4.9

3.5

3.2

3.3

na

0.09

8.6

0.26

0.05

0.24

0.36

0.31

0.72

5.0

2.8

3.7

5.1

4.5

3.8

2.3

3.4

3.1

3.8

0.99

Si

na

na

0.16

na

0.35

0.31

0.50

na

na

na

0.08

1.2

0.68

1.1

1.0

1.0

1.8

1.5

1.4

1.2

na

0

3.6

0.13

0

0.18

na

0.12

0.23

2.5

2.3

1.6

na

2.1

1.8

1.2

1.5

1.3

1.6

0.51

S2

na

na

0.16

na

0.52

0.42

0.61

na

na

na

0.06

1.7

1.5

2.2

1.7

1.6

3.3

2.0

1.8

2.0

na

0

5.9

0.17

0.08

0.33

na

0.42

1.7

19

22

16

na

18

15

7.0

12

11

15

2.8
Appendix 2, table 2. Lithologic, chemical, isotopic, and mineralogic data for core samples in study Continued.

Well name

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

State No. 1-16

State No. 1-16

State No. 1-16

State No. 1-16

State No. 1-16

State No. 1-16

State No. 1-16

State No. 1-16

State No. 1-16

State No. 1-16

State No. 1-16

State No. 1-16

Ute Mountain No. 44-34

Ute Mountain No. 44-34

Ute Mountain No. 44-34

Ute Mountain No. 44-34

Ute Mountain No. 44-34

Ute Mountain No. 44-34

Ute Mountain No. 44-34

Ute Mountain No. 44-34

Ute Mountain No. 44-34

West Water Creek No. 1

Depth 

(ft)

2552.8

2555.3

2556.5

2558.0

2559.5

2560.5

2562.0

2563.0

2564.0

2564.8

2566.0

2568.0

2576.0

2580.0

2884.0

2923.0

2940.0

2953.0

5518.3

5521.3

5537.0

5542.0

5546.8

5552.0

5698.0

5700.5

5701.8

5704.0

5707.7

5711.5

8695.0

8714.0

8720.0

8732.5

8737.0

8742.5

8753.0

8769.8

8773.0

6304.8

S0rg 

(weight percent)

na

0.06

na

0.01

na

na

0.03

O.01

0.03

0.02

0.01

O.01

na

O.01

0.1

na

na

O.01

O.01

na

0.01

O.01

O.01

O.01

0.01

na

0.51

0.06

0.04

0.03

na

na

O.01

O.01

O.01

O.01

0.01

O.01

O.01

O.01

(weight percent)

2.3

1.5

1.3

0.79

1.0

0.53

1.1

1.3

1.6

1.5

1.3

0.5

0.29

0.58

1.1

0.25

0.18

0.33

0.13

0.13

0.39

1.4

0.79

0.74

0.42

0.34

2.9

1.2

2.4

2.8

0.28

0.54

0.97

0.98

0.95

1.0

1.0

0.98

1.0

2.2

CC03 

(weight percent)

1.4

1.6

3.5

7.9

3.7

7.9

3

2.8

2.7

3.1

2.7

1.6

7.4

5.3

O.01

9.2

12

2.8

11

11

7.5

3.2

2.8

3.8

8.8

9.7

2.6

6.6

3.4

3.6

4.2

7.4

6.0

4.9

4.9

5.9

5.4

5.7

5.6

3.8

C0rg 

(weight percent)

3.0

3.3

2.3

1.3

2.4

1.8

2.0

1.9

1.8

1.8

2.0

0.05

0.76

0.13

17

4.7

2.1

0.26

0.07

0.07

0.11

0.41

0.25

0.36

0.27

0.19

3.3

1.3

2.6

2.4

0.22

0.25

0.93

1.0

1.1

1.1

1.5

1.3

1.3

1.8

Si

1.3

1.4

1.9

0.61

1.0

0.69

0.85

0.79

0.69

0.64

1.0

na

0.28

na

8.5

1.4

1.3

na

na

na

na

na

na

na

na

na

0.69

0.55

1.7

1.7

0

0

0.13

0.15

0.15

0.16

0.21

0.21

0.21

1.0

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8.6

12

7.8

3.4

7.5

4.4

6.0

5.5

4.5

4.2

6.0

na

0.94

na

50

14

9.0

na

na

na

na

na

na

na

na

na

9.1

4.3

8.7

9.0

0

0

0.11

0.15

0.12

0.15

0.22

0.18

0.20

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Appendix 2, table 3. Lithologic, chemical, isotopic, and mineralogic data for core samples in study Continued.

Well name

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

State No. 1-16

State No. 1-16

State No. 1-16

State No. 1-16

State No. 1-16

State No. 1-16

State No. 1-16

State No. 1-16

State No. 1-16

State No. 1-16

State No. 1-16

State No. 1-16

Ute Mountain No. 44-34

Ute Mountain No. 44-34

Ute Mountain No. 44-34

Ute Mountain No. 44-34

Depth 

(ft)

2545.0

2546.3

2547.3

2548.8

2550.5

2551.5

2552.8

2555.3

2556.5

2558.0

2559.5

2560.5

2562.0

2563.0

2564.0

2564.8

2566.0

2568.0

2576.0

2580.0

2884.0

2923.0

2940.0

2953.0

5518.3

5521.3

5537.0

5542.0

5546.8

5552.0

5698.0

5700.5

5701.8

5704.0

5707.7

5711.5

8695.0

8714.0

8720.0

8732.5

01

38

33

44

45

25

59

29

32

38

55

34

40

60

65

81

80

78

na

152

na

4

12

54

na

na

na

na

na

na

na

na

na

20

49

33

31

104

88

56

35

T1 max

439

435

436

440

438

438

433

437

436

437

435

437

437

435

436

437

436

na

436

na

434

435

436

na

na

na

na

na

na

na

na

na

452

444

446

445

415

na

462

469

5 SDl

-20.7

na

-26.8

-13.6

-24.0

-22.5

na

-25.7

na

-27.4

na

na

-31.5

-32.1

-31.9

-35.7

na

-12.6

na

-29.6

-44.9

na

na

-30.9

-23.8

na

-28.7

-21.3

-22.9

-20.9

-13.7

na

-9.4

-5.0

-7.7

-5.8

na

na

-23.3

-16.5

5 S so4

-3.6

na

-4.2

insuf

0.4

6.3

na

2.8

na

-0.8

na

na

-5.8

-5.5

-5.0

-6.2

na

-5.0

na

-4.3

-24.8

na

na

insuf

12.9

na

14.0

insuf

insuf

7.6

insuf

na

insuf

insuf

insuf

insuf

na

na

insuf

insuf

5 S0rg

na

na

insuf

insuf

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insuf

na

insuf

na

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na

na

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insuf

insuf

insuf

na

insuf

na

na

-23.4

na

na

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na

na

insuf

insuf

insuf

insuf

insuf

na

-8.0

-1.1

-0.7

insuf

na

na

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(weight perce

2.6

na

2.5

3.1

2.9

1.5

na

2.6

na

1.7

na

na

2.2

2.0

2.3

2.3

na

0.62

na

1.3

1.2

na

na

0.84

<05

na

0.39

1.5

0.91

0.92

0.36

na

2.4

1.0

2.4

2.6

na

na

1.2

1.1
N66 EVOLUTION OF SEDIMENTARY BASINS PARADOX BASIN

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Appendix 2, table 4. Lithologic, chemical, isotopic, and mineralogic data for core samples in study Continued.

Well name

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

ShaferNo. 1

State No. 1-16

State No. 1-16

State No. 1-16

State No. 1-16

State No. 1-16

State No. 1-16

State No. 1-16

State No. 1-16

State No. 1-16

Depth 

(ft)

2536.5

2537.0

2539.0

2540.0

2541.0

2542.8

2543.8

2545.0

2546.3

2547.3

2548.8

2550.5

2551.5

2552.8

2555.3

2556.5

2558.0

2559.5

2560.5

2562.0

2563.0

2564.0

2564.8

2566.0

2568.0

2576.0

2580.0

2884.0

2923.0

2940.0

2953.0

5518.3

5521.3

5537.0

5542.0

5546.8

5552.0

5698.0

5700.5

5701.8

Potassium 

feldspar

5

6

15

10

11

12

11

11

11

16

13

14

5

16

18

14

6

15

8

19

18

19

16

14

33

9

15

39

27

2

21

0

0

4

11

0

5

0

0

0

Sodium 

feldspar

4

5

14

10

10

11

10

9

8

11

10

11

5

13

13

10

5

11

6

0

0

0

0

0

13

0

8

0

0

0

0

3

0

4

8

6

11

13

9

13

Apatite

0

0

0

17

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

30

8

0

0

0

0

0

0

3

0

0

0

7

Calcite

0

0

0

29

63

61

72

74

0

59

66

17

7

0

30

15

9

6

17

82

61

56

53

61

4

5

5

0

0

0

22

245

356

189

78

63

75

122

145

67

Dolomite

213

193

71

44

24

25

26

26

130

23

28

45

210

38

31

74

153

87

206

28

18

19

21

23

66

190

137

13

59

303

90

0

32

50

40

29

55

103

120

15

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3

0

0

0

0

6

0

6

5

6

0

0

3

0

0

6

4

0

4

0

0

0

10

11

0

0

4

19

9

0

0

0

0

0

4

4

0

0

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Well name

Gibson Dome No. 1

Gibson Dome No. 1

Gibson Dome No. 1

Gibson Dome No. 1

Honaker Trail outcrop

Lake Canyon No. 1-27

Lake Canyon No. 1-27

Lake Canyon No. 1-27

Lake Canyon No. 1-27

Lake Canyon No. 1-27

Lake Canyon No. 1-27

Lake Canyon No. 1-27

Lake Canyon No. 1-27

Lake Canyon No. 1-27

Norton Federal No. 1-4

Norton Federal No. 1-4

Norton Federal No. 1-4

Norton Federal No. 1-4

Norton Federal No. 1-4

Norton Federal No. 1-4

Norton Federal No. 1-4

Norton Federal No. 1-4

Norton Federal No. 1-4

Norton Federal No. 1-4

Norton Federal No. 1-4

Norton Federal No. 1-4

Norton Federal No. 1-4

Norton Federal No. 1-4

Norton Federal No. 1-4

Pickett Federal No. 1-33

Pickett Federal No. 1-33

Pickett Federal No. 1-33

Pickett Federal No. 1-33

Pickett Federal No. 1-33

Pickett Federal No. 1-33

Pickett Federal No. 1-33

Pickett Federal No. 1-33

Pickett Federal No. 1-33

Pickett Federal No. 1-33

Pickett Federal No. 1-33

Depth 

(ft)

3096.3

3098.2

3098.6

3110.2

0.0

5748.5

5749.0

5752.8

5756.5

5762.3

5764.5

5767.0

5770.3

5774.5

5919.8

5925.0

5929.0

5929.8

6042.0

6044.3

6052.3

6057.5

6060.3

6062.3

6066.0

6067.8

6071.5

6074.5

6077.3

5642.0

5644.3

5645.8

5648.0

5649.0

5651.2

5653.3

5656.5

5659.0

5660.8

5664.0

Total clay

6

10

0

7

11

3

12

10

8

6

9

10

10

18

7

8

8

9

0

4

8

6

8

10

11

11

11

0

0

4

11

13

14

15

15

15

16

18

20

13

Al

(wt. %)

2.7

3.6

0.71

2.9

4.7

1.3

5.5

3.8

3.8

3.1

4.1

4.3

4.9

7.3

3.1

3.6

3.3

3.5

0.03

1.3

3.2

2.1

2.9

5.4

7.3

7.9

4.5

0.53

0.18

1.1

5.0

6.2

5.5

6.1

6.2

5.8

6.3

6.7

7.5

5.5

Ca

(wt. %)

8.8

6.1

24

5.7

14

25

11

16

17

17

17

16

15

6.9

18

17

17

17

24

20

12

14

14

8.3

2.6

2.0

4.7

24

25

29

16

10

12

9.9

9.1

11

8.3

7.5

4.1

12

Fe 

(wt. %)

1.2

1.3

0.35

0.91

2.5

0.93

2.7

2.0

2.0

5.6

2.1

2.0

2.3

2.6

1.5

1.7

1.6

1.6

0.38

0.87

1.4

1.1

1.6

1.9

2.0

2.0

1.9

0.24

0.39

0.67

2.4

2.5

2.5

2.7

3.1

2.7

3.0

2.9

2.9

2.7

K 

(wt. %)

2.6

2.6

0.69

2.4

2.7

0.44

2.3

1.5

1.4

1.1

1.6

1.7

1.8

2.9

1.4

1.5

1.4

1.4

0.03

1.1

2.4

1.3

1.9

4.3

6.2

7.6

3.2

0.52

0.22

0.56

2.4

3.0

2.6

2.9

3.2

2.7

3.4

3.7

3.9

3.3

Mg 

(wt. %)

5.1

6.3

2.9

4.5

2.6

5.7

3.7

3.3

3.8

2.8

3.1

3.2

3.0

2.6

3.9

3.4

3.4

3.0

15

15

10

9.7

11

3.8

3.4

2.5

5.8

1.7

14

4.1

3.7

2.5

2.7

2.7

2.5

2.7

2.4

2.4

2.3

3.7

Na 

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4.6

1.1

0.7

3.9

0.2

0.4

0.9

0.5

0.5

0.4

0.5

0.5

0.6

0.9

0.1

0.1

0.1

0.1

0.0

0.0

0.1

0.0

0.1

0.1

0.1

0.1

0.1

0.0

0.0

0.0

0.2

0.3

0.2

0.3

0.2

0.3

0.2

0.2

0.3

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Well name

Pickett Federal No. 1-33

Pickett Federal No. 1-33

Pickett Federal No. 1-33

Pickett Federal No. 1-33

Pickett Federal No. 1-33

Pickett Federal No. 1-33

Pickett Federal No. 1-33

Pickett Federal No. 1-33

Pickett Federal No. 1-33

Pickett Federal No. 1-33

Pickett Federal No. 1-33

Pickett Federal No. 1-33

Shafer No. 1

Shafer No. 1

Shafer No. 1

Shafer No. 1

Shafer No. 1

Shafer No. 1

Shafer No. 1

Shafer No. 1

Shafer No. 1

Shafer No. 1

Shafer No. 1

Shafer No. 1

Shafer No. 1

Shafer No. 1

Shafer No. 1

Shafer No. 1

Shafer No. 1

Shafer No. 1

Shafer No. 1

Shafer No. 1

Shafer No. 1

Shafer No. 1

Shafer No. 1

Shafer No. 1

Shafer No. 1

Shafer No. 1

Shafer No. 1

Shafer No. 1

Depth 

(ft)

5645.8

5648.0

5649.0

5651.2

5653.3

5656.5

5659.0

5660.8

5664.0

5665.5

5665.8

5670.5

2514.5

2529.0

2535.0

2536.5

2537.0

2539.0

2540.0

2541.0

2542.8

2543.8

2545.0

2546.3

2547.3

2548.8

2550.5

2551.5

2552.8

2555.3

2556.5

2558.0

2559.5

2560.5

2562.0

2563.0

2564.0

2564.8

2566.0

2568.0

Sc 

(ppm)

13

11

12

13

12

13

13

15

11

3

9

7

1

5

5

3

5

10

11

13

12

12

12

10

13

13

13

6

13

10

14

8

12

7

13

13

13

13

13

1

Se 

(ppm)

na

na

na

na

na

na

na

na

na

na

na

na

na

na

na

na

na

na

11

9

18

14

11

4.7

9

12

7.7

2.8

7.9

na

4.2

2.8

4.3

1.9

4.4

3.4

4.5

4.1

na

na

Sr 

(ppm)

230

250

210

200

220

205

190

150

200

200

260

150

1500

160

140

130

140

180

200

260

240

260

260

150

240

250

190

150

195

210

180

160

170

140

270

270

270

290

285

100

V 

(ppm)

100

100

90

130

87

99

110

140

88

22

160

48

4

40

39

26

44

150

92

99

120

110

120

77

110

100

120

43

110

130

99

47

89

40

94

95

100

99

105

5

Y 

(ppm)

24

32

29

40

30

31

33

24

33

14

26

10

1

12

12

18

17

20

59

30

29

43

33

27

35

30

34

23

33

27

30

27

28

25

25

22

24

27

23

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