19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

?

? Calcareous

Slightly fissile

Fissile

Fissile

Fissile

Dolomite

Fissile

Fissile

Steel blue

Prominent ledge

Discontinuous yellow tuff

1–3 in thick dol. beds

Fissile

.5 in–2 in thick 

dolomite beds

Fissile

.5 in–2 in thick 

dolomite beds

Hard, nonfissile

conspicuous

light band

Fissile

Fissile

Not fissile

Fissile, .5 in–2 in thick

dolomite beds

Fissile

2 in yellow siltstone

Not fissile

Not fissile

1 in tuff, even top

and base

Fissile

Fissile

Fissile

Fissile

Syneresis cracks

8 in dol. bed

Fissile to

not fissile

4 in dol. bed

4 in white tuff

1 in–3 in pinching tuff

1 in pinching tuff

.5 in rich bed

Several thin

tuffs

1 in tuff

8

7

6

5

4

3

2

1

0

7

6

5

4

3

2

1

0

17

16

15

14

13

12

11

10

9

18

19

20

Micritic limestone with

ostracode lenses and 

layers

Fissile shale

Fissile shale

Fissile shale

Fissile shale

Fissile shale

Badly covered olive-gray mudstone 

Dolomitic

1–2 in thick dolomite beds

1–2 in thick tufa layers in gray mudstone

Tufa layers in dolomitic siltstone

Calcareous and dolomitic mudstone

interbedded with fissile dark shale

Calcareous and dolomitic mudstone

interbedded with fissile dark shale

Dolomitic mudstone

Dolomitic mudstone

All covered, stromatolitic

debris in slope

Stromatolite on top of sandstone

Some stromatolite debris

Calc.

Lean to moderate, flakey, 2 ft thick

Lean to moderate, flakey, 2 ft thick

Lean to moderate, flakey, 3 ft thick

Syneresis cracks

Syneresis cracks

Dolomite beds to 2 in,

some thin oil shale beds

Dolomite beds to 2 in,

some thin oil shale beds

Lean to moderate, 4.3 ft thick

Lean to moderate, 4.3 ft thick

Lean, flakey, 6.9 ft thick

Very lean to barren, 10.3 ft thick 

Dolomitic

Dolomitic

Stromatolitic ripups

Stromatolitic ripups

8

17

16

15

14

13

12

11

10

9

18

19

20

Oncolites to 0.25 in diameter

Oncolitic algal layer in middle

5% very-fine silty sandstone beds to 4 in

Sanding upwards cycle

Ostracodes along laminae

Two thin zones of algal 

ripups near base

Syneresis cracks near base

Syneresis cracks 

0.5 ft thick massive dolomite bed

Some marlstone zones

Lean, 1 ft thick

Very-lean, 4.2 ft thick

Stromatolite debris

Massive, nonlaminated

Sandy near top

Silty marl

Silty and poorly laminated

near top

T

T

Very-lean, 8.9 ft thick

Very-lean, 3.1 ft thick

2 inch thick tuff

2.5 inch thick tuff

Stromatolite ripups

Discontinuous, 0.5 ft thick

Silty and sandy towards top

Coarsening upwards, 6.3 ft thick

Syneresis cracks 

Abundant dark mineral

Abundant dark mineral

Dolomite beds to 0.5 ft 

thick in upper part

Lots of stromatolitic debris in covered

slope

Some stromatolites and very-fine

sandstone beds

bioturbated

Gyp

bioturbated

Gyp

Gyp

Gyp

Gyp

bioturbated

5% non-laminated

silt beds

30% ostracod beds

10% ostracod beds

3% sand beds

5% dolomite beds

30% clay beds

LLH/LLH

syneresis cracks

& mud volcanos

syneresis cracks

syneresis cracks

LLH

syneresis cracks

siltstone beds are 

lenticular and rippled

syneresis cracks

syneresis cracks

syneresis cracks

syneresis cracks

clastic dikes

SLH/LLH

clastic dikes

2 in thick tuff

ripups to 6 in

even top & base, persistent

even top & base.

 very persistent

SLH?

SLH?

syneresis cracks

calcareous ripups as 

large as 2 ft lower

6 ft of unit

yellow weathering, 

even top & bottom

gradational contacts,

syneresis cracks

coarsens upward

sharp base

sharp top and base

sharp base, persistent

sharp base, persistent

clastic dikes

SLH

sharp top & base

SLH/SLH, SLH/LLH

Minor contorting,

rust weathering

Highly contorted,

rust weathering

Highly contorted,

rust weathering

Rust weathering

Rust weathering

Rust weathering

Rust weathering

Rust weathering

Siltstone, marl, and Ss, 

syneresis cracks

White marl

White marl

Very lean, 2 ft thick

Can’t see bedding, rust weathering

Can’t see bedding, rust weathering

Bioturbated, rust weathering

Bright white marl

Large-scale southward

directed slumping

Minor contorting,

rust weathering

Minor contorting,

rust weathering

Interbedded Sandstone

and silty marl

Mostly indistinct bedding,

dark minerals along some

laminae, rust weathering

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

33

32

?

34

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

33

32

34

0 20 40 60 80 100

0 20 40 60 80 100

35

36

37

38

39

-10

-9

-8

-7

-6

-5

-4

-3

-2

-1

-15

-14

-13

-12

-11

0 20 40 60 80 100

0 20 40 60 80 100

C-329

Carter Oil Co., Opportunity 2, 

2,150 FEL, 850 FNL

sec. 28, T. 1 N., R. 96 W.

500

1,000

1,500

2,000

0

0 20 40 60 80 100

0 20 40 60 80 100

C0187

Superior Oil Co., Core hole 03

Sec. 10, T. 1 N., R. 97 W.

500

1,000

1,500

0

+1

+3

+2

0 20 40 60 80 100

0 20 40 60 80 100

C0173

U.S. Bureau of Mines, Barcus Creek 1

Sec. 21, T. 1 N, R. 99 W

500

1,000

1,500

2,000

0

9

10

0 20 40 60 80 100

0 20 40 60 80 100

C0160

Carter Oil Co. Opportunity Block 1

775 FWL, 375 FSL, Sec. 2, T. 1 S., R. 96 W.

GL 6,750 ft

500

1,000

+100

400

300

200

100

0

1,500

2,000

2,100

2,200

2,300

2,400

2,500

2,600

2,700

2,800

2,900

3,000

3,100

0 20 40 60 80 100

0 20 40 60 80 100

C0016

Weber Oil Co., Juhan 1

250 FEL, 2,190 FSL

Sec. 2, T. 1 S., R. 96 W.

GL 6,315 ft

500

1,000

0

1,100

1,200

1,300

1,400

1,500

1,600

1,700

1,800

1,900

2,000

2,100

2,200

2,300

+100

+200

+200

+300

600

700

800

900

1,000

1,100

1,200

1,300

600

700

800

900

1,000

1,100

1,200

+100

+200

+300

+400

+500

Oil yield (gallons per ton)

8

7

Oil yield (gallons per ton)

Oil yield (gallons per ton)

Oil yield (gallons per ton)

Oil yield (gallons per ton)

Oil yield (gallons per ton)

Oil yield (gallons per ton)

Oil yield (gallons per ton)

Oil yield (gallons per ton)

Oil yield (gallons per ton)

Oil yield (gallons per ton)

Oil yield (gallons per ton)

Oil yield (gallons per ton)

Oil yield (gallons per ton)

Oil yield (gallons per ton)

Very-lean

Lean

Lean-to-moderate

Moderate

Moderate-to-rich

Rich

Very-rich

Rich-to-very-rich

Very-lean

Lean

Lean-to-moderate

Moderate

Moderate-to-rich

Rich

Very-rich

Rich-to-very-rich

Very-lean

Lean

Lean-to-moderate

Moderate

Moderate-to-rich

Rich

Very-rich

Rich-to-very-rich

Very-leanLeanLean-to-moderateModerate

Moderate-to-richRichRich-to-very-rich

Very-rich

27

26

25

24

23

22

21

20

19

34

33

32

31

29

28

30

C0499

Geokinetics Inc.

Jacqueline 24

Sec. 16, T. 2 N., R. 98 W.

TD ? ft

Very-leanLeanLean-to-moderateModerate

Moderate-to-richRichRich-to-very-rich

Very-rich

Estimated oil yield

Very-leanLeanLean-to-moderateModerate

Moderate-to-rich

RichRich-to-very-rich

Very-rich

Estimated oil yield

Estimated oil yield Estimated oil yield

Estimated oil yield

Estimated oil yield

Very-leanLeanLean-to-moderateModerate

Moderate-to-richRichRich-to-very-rich

Very-rich

Estimated oil yield

Estimated oil yield

Very-leanLeanLean-to-moderateModerate

Moderate-to-richRichRich-to-very-rich

Very-rich

Estimated oil yield

Estimated oil yield

0

100

200

300

400

500

6.7 GPT

R-5: 200 ft

?

?

?

Marlstone at Trail Canyon

Marlstone at Trail Canyon

unnamed tongue of Green River Formation

unnamed tongue of Green River Formation

Yellow Creek measured section

Secs. 10, 15, 16, 17, T. 2 N., R. 98 W.

Spring Creek measured section

Secs. 2, 11, T. 2 N., R. 99 W.

Lower Piceance Creek measured section

Secs. 11, 12, 14, T. 1 N., R. 97 W.

R–1 oil shale zone

R–0 oil shale zone (part)

L–1 oil shale zone

L–0 oil shale zone

R–2 oil shale zone

L–2 oil shale zone

R–3 oil shale zone

L–3 oil shale zone

R–4 oil shale zone

L–4 oil shale zone

R–5 oil shale zone

R–5 oil shale zone

L–5 oil shale zone

R–6 oil shale zone

B–groove

A–groove

Mahogany oil shale zone

Mahogany oil shale zone

R–1 oil shale zone

R–0 oil shale zone (part)

L–1 oil shale zone

L–0 oil shale zone

R–2 oil shale zone

L–2 oil shale zone

R–3 oil shale zone

L–3 oil shale zone

R–4 oil shale zone

L–4 oil shale zone

R–5 oil shale zone

L–5 oil shale zone

R–6 oil shale zone

B–groove

A–groove

Mahogany oil shale zone

Mahogany oil shale zone

Garden Gulch

Member

Anvil Points

Member

Parachute Creek

Member

Dry Fork Tongue

of Green River Fm.

Thirteenmile Cr. Tongue

of Green River Fm.

Uinta Formation

Uinta Formation

Uinta Formation

Uinta Formation

Uinta Formation

Yellow Creek Tongue of Green River Formation

unnamed tongue of

Green River Formation

Unnamed tongue 2 of Green River Formation (Hail, 1988)

Uinta Formation

(not mapped by Hail, 1988)

Uinta Formation

Uinta Formation

Uinta Formation

Uinta Formation

Uinta Formation

Uinta Formation

Uinta Formation

Uinta Formation

Uinta Formation

Uinta Formation

Parachute Creek Member

of Hail (1974)

Garden Gulch Member

of Hail (1974)

Basal sandstone mbr.

of Hail (1974)

Base of Long Point Bed of the Green River Formation (Johnson, 1984)

0.5 miles 3.5 miles 6.7 miles 5.0 miles 5.4 miles 1.3 miles 2.3 miles 0.5 miles 5.0 miles 3.1 miles 0.9 miles 1.0 miles 4.0 miles 

0 20 40 60 80 100

0 20 40 60 80 100

C0358

U.S. Geological Survey

Core hole 78–5

Sec. 32, T. 2 N., R. 97 W.

500

0

0 20 40 60 80 100

0 20 40 60 80 100

C0498

Geokinetics Inc.

Florence 8

Sec. 4, T. 1 N., R. 97 W.

500

0

6

5

4

3

2

1

0

Hay Gulch measured section

Sec. 36, T. 1 N., R. 96 W.

Sec. 1, T. 1 S., R. 96 W.

0.3 ft thick, very rich, carbonate ripups

0.3 ft thick, very rich, carbonate ripups

Lean

Rich

6

5

4

3

2

1

0

1.5 ft thick, lean to moderate, marlstone 

ripups, 2 in pinching tuff

8 ft thick, lean, 4 ft rich in middle, 

0.6 ft rippled Ss 2 ft from base

Silty marl grading up into Ss

Small marlstone ripups in lower part

5 ft thick, lean-very lean to barren

3 ft thick, very-lean to barren

10 ft thick, lean to very-lean 

18.7 ft thick, very-lean 

38 ft thick, very-lean 

12 ft thick, very-lean 

10 ft thick, very-lean 

1 ft thick, moderate 

1.5 ft thick, lean to moderate 

6 ft thick, lean with 1 ft 

moderate to rich at top

16.5 ft thick, lean with two

1 ft thick moderate beds

1 ft thick, moderate 

1 ft thick, moderate to rich 

18.3 ft thick, moderate to very-rich, 

Mahogany Bed 

2 ft thick tuff 

8 ft thick,, moderate to rich, rich 

beds have marlstone ripups 

Silty marl with possibly 

some very-lean

14 ft thick, very lean with two lean to 

moderate beds 1.5 ft and 2 ft thick 

9 ft thick, moderate, 3 tuffs to 0.2 ft 

1.5 ft thick, moderate with very-rich 

beds containing marlstone ripups 

Some possible very-lean 

Olive-gray mudstone grading up 

into white marl 

0.3 ft thick, calcareous inconspicuous bedding 

No dark grains 

Insect parts 

Some thin very-fine Ss beds 

Mostly lean oil shale with three 

thin, very-rich blue beds with 

marlstone ripups, includes a 2.4 ft 

thick Ss with troughs 

10 ft thick, lean to very-lean 

3.7 ft thick, moderate 

11 ft thick, very-lean to moderate

11 ft thick, very lean to moderate 

with a 1.5 ft thick very-rich bed

10 ft thick, very-lean to barren

Bidirectional troughs

Dolomitic mudstone

Very lean and dolomitic mudstone

Algal ripups at top

Algal ripups at top

Barren white marlstone

Barren white marlstone

Barren white marlstone

Barren white marlstone

Barren white marlstone

Dolomitic siltstone with very-fine

sandstone beds grading up into 

barren marl to very lean

Minor barren white marlstone

Barren white marlstone

8

7

6

5

4

3

2

1

0

Buff

Light

Medium

Dark

Black

Purple

Maroon

Clay

Silt

Very-Fine

Fine

Medium

Coarse

Conglomerate

11

10

9

09–03, 09–04, 

Smith Gulch measured section

Sec. 14, T. 1 N., R. 96 

2% dark chert

2% dark chert

Indistinct laminae, 2% dark chert

Slightly fissile

Slightly fissile

Fissile

Fissile

Fissile

Fissile

Mudstone, not fissile

Moderately fissile

No bedding seen

No bedding seen

2 in ostracodal limestone

No bedding seen

Thin Ss and ost.beds

0.3 ft thick

2% dark chert

2% dark chert

2% dark chert

2% dark chert

Very slightly calcareous

2 inch thick tuff

Plant remains througout

Slightly fissile

Slightly fissile, dolomitic

Slightly fissile, dolomitic

4 in ostracodal Ls overlying Ss

Mud ripups near top

0.2 ft thick, large calcite crystals

Weakly laminated, some 1–2 in

thick dolomite beds near base

Weakly laminated, dolomitic,

becoming siltier towards top

Tan massive siltstone

Becomes interbedded with

very-fine Ss near top

6 in thick, well laminated, laterally linked hemispheriods

7 ft thick fissile oil shale bed, 

lower 5 ft lean, upper 2 ft rich

7 ft thick fissile oil shale bed, 

alternating rich and lean zones

Slightly fissile

Sandy

10 ft thick, lean to very-lean fissile

Algal ripups, black chert grains

Dolomitic, 3 in ost. Ls near base

Interbedded siltstone and mudstone

Sandy ostracodal limestone

1.5 ft thick algal layer

Calcareous and dolomitic, some

thin, rust-weathering siltstones

0.4 ft thick, abundant rusty grains

2 ft thick

Full of marlstone ripups

Moderately rich, fissile, 2 ft thick

Moderately rich, fissile, 0.5 ft thick

Dolomitic, moderately fissile

Indistinct bedding, syneresis cracks on bottom

Marlstone ripups to 3 × .25 in

10–20% rounded buff grains

10–20% rounded buff grains, 1.5 ft thick

30–40% small marlstone ripups

Rare small marlstone ripups

Full of marlstone ripups

Interbedded with silstone in

lower 2 ft, a few ripups

Marlstone ripups to 4 × .5 in

Dolomitic

Dolomitic

Mudstone parting

Algal ripups to 0.5 in

Ss beds to 3 in, dolomitic concretions to 3 × 1 in

Weakly laminated, dolomitic, 

a few ostracodes

Very lean, 1 ft thick

Weakly laminated, dolomitic

Mudstone bed near top

Dolomite beds to 4 in thick

Dolomitic, slightly fissile

Possibly minor kerogen

Dolomitic

Dolomitic

Dolomitic

Dolomitic

Fissile, 1 in dolomite bed near top

Lean, 4 ft thick

Lean to moderate, fissile, 4 ft thick

5% chert, sparry calcite cemented

Lean, fissile, 2 ft thick

Fissile

Fissile

White barren marl

White barren marl

Moderate-rich, 3 ft thick, thin Ss

very-lean to rich, 9 ft thick

Grades upwards from very-lean to mod.

Marlstone ripups

8

7

6

5

4

3

2

1

0

Buff

Light

Medium

Dark

Black

Purple

Maroon

Clay

Silt

Very-Fine

Fine

Medium

Coarse

Conglomerate

15

14

13

12

11

10

Very-lean

Lean

Lean-to-moderate

Moderate

Moderate-to-rich

Rich

Very-rich

Rich-to-very-rich

18

8

7

6

5

4

3

2

1

0

17

16

15

14

13

12

11

10

9

18

2 in pinching tuff

Carbonate ripups, 3 pinching tuffs to 1 in

Some pinching bedding

2.5–4 in tuff, Mahogany Marker

Chevron folds

Dolomite beds and nodules

Nonlaminated

Nonlaminated

Nonlaminated

Nonlaminated

Nonlaminated

Nonlaminated

Nonlaminated

Nonlaminated

Nonlaminated

Mostly nonlaminated

Nonlaminated, bright white

Large unusual crystals

Blades of calcite

Carbonate and black chert grains

Black chert, secondary 

calcite, pinches out 

100 ft along outcrop 

Mostly light gray

Mostly light gray

Sharp base

Sharp base, persistent

Goniobasis, viviparids

Slightly fissile

Small scour-and fill channels

A few ostracode 

beds to 1 in thick

15% light mud laminae

4 in thick

2 ft thick

0.7 ft thick

Some sand, carbonate ripups

slightly fissile, thin ostracode beds

10% light mud beds to 1 in

Ostracode beds to 4 in, 

carbonate ripups

one 2-inch dolomite bed

Dol

Dolomite concretions to 

10 in, distinctive cracks

Thin ostracodal Ss beds

Fissile, 5% dolomite 

beds to 2 in thick

Rich, fissile, 2 ft thick

Fissile, very few

dolomite beds

1 in thick tuff in rich oil shale

Slightly fissile

Slightly fissile, dolomitic

Slightly fissile, dolomitic

Moderately fissile

Moderately fissile

Very fissile

Interbedded shale and oil shale

Fissile, dolomite beds to 1 in

Dolomitic

Dolomitic

Dolomitic

Dolomitic

Dolomite concretions to 2 in.

1-in thick dolomite bed at top

Dolomitic, some verylean oil shale zones

Tuff, 3–4 in thick, locally to 6 in thick

Carbonate ripups near base

Rich beds split by lean bed, carbonate ripups

Carbonate ripups

Nahcolite vugs to 6 in

Hard, dolomitic, buff

dolomite beds to 2 in

Carbonate ripups near top

Carbonate ripups near top

and base well laminated in 

middle

Carbonate ripups to 4 in

Carbonate ripups

Carbonate ripups

Pinching tuff to 2 in 

Rich and moderately-rich bands

Three 1-inch rich beds

All well-laminated 

siltstone

2 in tuff 6 in below rich bed

1 in pinching tuff 

Nahcolite vugs to 18 in

Distinctive droopy ledge

Hard, platy marl

Rust-weathering silty sandstone,

no discernible bedding, but 

exposure is poor

No apparent bedding

Mostly indistinct bedding,

bright, volcanic quartz,

5% dark grains

Chaotic 

Interbedded very-lean

oil shale and white marl

Tuffaceous lenses

Fissile, a few dolomite 

beds to 2 in thick

Fissile

Fissile, dolomitic

Fissile

Fissile

Fissile, alternating rich

and lean beds

Thin dolomite beds, 

carbonate ripups

Possible insects

5 in thick sandy silstone

Some very-lean oil shale

Some very-lean oil shale

Hard, dolomitic

White marl

White marl

600

700

800

900

1,000

16

17

9

Very lean 2 ft thick

Interbedded shale and oil shale

Fissile dolomitic

1-in thick dolomite bed at top

Nonlaminated

Green River Formation

Anvil Points Member (lower part) Garden Gulch Member Parachute Creek Mbr. Anvil Points Mbr. (upper part)

Stratigraphic subdivisions

from Pipiringos and Johnson (1976)

Pisolite ledge

First algal zone 

Yellow tuff bed 

Lower ostracodal 

limestone

Green River Formation Green River Formation

Garden Gulch Member

lower part Garden Gulch Member upper part (Tggu) Parachute Creek Member

Uinta Formation

(part) Marlstone at Trail Canyon

Stratigraphic subdivisions

from Donnell and Hail (1984)

?

?

?

?

Maroon

Buff

Light

Medium

Dark

Black

Purple

Clay

Silt

Very-Fine

Fine

Medium

Coarse

Conglomerate

Very-lean

Lean-to-moderate

Moderate

Moderate-to-rich

Very-rich

Rich-to-very-rich

3 in thick, mapped as yt (yellow tuff bed)

Mahogany oil shale bed

Mahogany oil 

shale bed

Mahogany oil shale bed

Mahogany oil shale bed

Mahogany oil shale zone

Mahogany oil shale zone

Yellow tuff bed 

Yellow tuff bed 

Yellow tuff bed

Creek or river Highway

Core hole

Cross section

T

2

N

T

1

N

T

1

S

T

2

S

T

3

S

T

4

S

T

5

S

T

8

S

T

7

S

T

6

S

108°30' 108°00’

City or town

Area underlain by the Mahogany bed County line 

Explanation

Colorado

T 102 W T 101 W T 99 W T 98 W T 97 W T 96 W T 100 W T 95 W T 94 W

40°00’

39° 30'

Piceance

White River

Meeker

Rangely

Rifle

Rio Blanco

DeBeque

Parachute

Colorado River

Creek

Creek

GARFIELD

RIO BLANCO

GARFIELD

MESA

Roan

White

River

Index map

Fletcher

Gulch

Spring

Creek

Yellow

Creek

C0499

C0173

C0498

C0358

C0187

C0016 C0160

Oil yield— In gallons per ton

Contact, dashed where approximate

Cross section scale

USGS number

Company name

Well name

Location (section, township, range)

0

100

150

200 FEET

Total depth of well— in feet

C0189

Superior Oil Co.

Core hole 05

sec. 10, T. 1 N., R. 97 W.

TD 1,393 ft.

Pelcypod

Climbing ripples

Symmetrical ripples

Horizontal stratification

Internal characteristics

Irregular stratification

Contorted stratification

Claystone, clayshale

or mudstone

Siltstone

Sandstone

Lithology

Oil Shale

Calcareous or dolomitic 

rock

Ostracodes

Gastropods

Oolites

Oncolites

Calcareous sandstone

Calcareous siltstone

Thin beds of dolomite

Pebbles and cobbles

Cross-stratification, less than 1 ft high

Cross-stratification, 1 to 3 ft high

Cross-stratification, greater than 3 ft high

Cross-stratification, 

less than 15 degrees

Ripples, nonspecific

Horizontal burrows

Fish bones or fish scales

Plant remains

LLH Laterally linked hemispheroids (stromatolites)

LLH/LLH Laterally linked hemispheroids that internally have

 small–scale laterally linked hemispheroids

Tuff

Stromatolites

Large-scale

lateral 

accretion

10

11

12

Mainly climbing ripples

Buff to white

Light gray/green

Medium gray/green

Dark gray/green

Black

Purple

Maroon

Pebbles and cobbles

Coarse sand

Medium sand

Fine sand

Very-fine sand

Silt

Clay

Covered

Irregular 

scour surface

Pinches out

along outcrop

Thins along 

 outcrop

Partially 

covered

Unweathered color Lithology Grain-size range Internal characteristics

Key to Measured Sections

Hundreds of

feet

Carbonaceous or woody

material

Ripup clasts

Limestone

Veinlets

Fossil bones

Mudcracks

Hummocky stratification

SLH/SLH Space linked hemispheroids that internally have

 small–scale space linked hemispheroids

SLH/LLH Space linked hemispheroids that internally have

 small–scale laterally linked hemispheroids

Indistinct laminae Feature near top of bed

Feature near base of bed

50

Explanation

Dol Dolomite concretions

T. 102 W. T. 101 W. T. 100 W. T. 99 W. T. 98 W. T. 97 W. T. 96 W. T. 95 W. T. 94 W. T. 93 W.

Piceance

Creek

Smith Gulch

A

A'

Olive gray

Offset in 

section

64

139 64

Hay Gulch

13

C0329

Fletcher

Gulch Measured section

139

Parachute

Creek

13

70

Fly larva

Carbonate-rich oil shale (>10 gallons per ton) 

Carbonate-rich oil shale (<10 gallons per ton) 

Clay-rich oil shale (>10 gallons per ton) 

Clay-rich oil shale (<10 gallons per ton) 

Variegated mudstone, sandstone, and siltstone 

Carbonate-rich mudstone with ostracodal,

oolitic, and stromatolitic limestone and 

minor sandstone and siltstone

Carbonate-rich mudstone with sandstone and 

siltstone and minor ostracodal, oolitic, and 

stromatolitic limestone

Volcaniclastic rocks 

Mostly oil shale with some volcaniclastic

material

0 6 12 MILES

0 6 12 KILOMETERS

Cross section A–A’ of the Eocene Green River Formation Along the North Margin of the Piceance Basin, Western Colorado

By

Ronald C. Johnson

2014

Any use of trade, firm, or product names is for descriptive purposes only and does 

not imply endorsement by the U.S. Government.

Although this information product, for the most part, is in the public domain, it also 

contains copyrighted materials as noted in the text. Permission to reproduce 

copyrighted items must be secured from the copyright owner.

For more information concerning this publication, contact:

Center Director, USGS Central Energy Resources Science Center

Box 25046, Mail Stop 939

Denver, CO 80225

(303)236-1647

Or visit the Central Energy Resources Science Center Web site at:

http://energy.usgs.gov/ 

Publishing support provided by: 

Denver Publishing Service Center

Manuscript approved for publication August 9, 2013

This and other USGS information products are available at

http://store.usgs.gov/ 

U.S. Geological Survey

Box 25286, Denver Federal Center

Denver, CO 80225

To learn about the USGS and its information products visit

http://www.usgs.gov/ 

1-888-ASK-USGS

This report is available at:

http://pubs.usgs.gov/sim/3276

Suggested citation:

Johnson, R.C., 2014, Detailed cross sections of the Eocene Green River Formation 

along the north and east margins of the Piceance Basin, western Colorado, using 

measured sections and drill hole information: U.S. Geological Survey Scientific 

Investigations Map 3276, 9 p., 11 sheets, http://dx.doi.org/10.3133/sim3276/.

U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Map 3276

Sheet 1 of 2

Pamphlet accompanies map

A

West

A'

East

Fletcher Gulch, measured section

Secs. 12, 14, T. 1 N., R. 100 W.

ISSN 2329-132X (online)

http://dx.doi.org/10.3133/sim 3276