?

? ? ?

?

?

?

?

?

?

Laramie River

Laramie River

Laramie River

Boxelder Creek

Slab CanyonWash

North Fork Cachela Poudre River

Buckhorn Creek

Redstone Creek

HorsetoothReservoir

Cache la Poudre River

YXu

Pgl Pf

Pf

Kbm

Pgl

Jmsj Kd Prgu

KnKbm Kd

Kss

Prgu

YXu

YXu

BULL MOUNTAIN

STINK CREEK FAULT

SHELL CREEK FAULT

LARAMIE BASIN

? ?

LARAMIE RIVER VALLEY

Jmsj

NORTH MIDDLEMTN THRUST FAULT

BULL MOUNTAIN FAULT

A A'

Quaternary deposits are not shown.

3,000

2,000

1,000

0

METERS

3,000

2,000

1,000

0

METERS

Sea Level

YXu

YXu

Kss

Kss

Pgl

Kd

Pf

Kbm Prgu

Kn Kss Nn NORTH MIDDLE

WEST JIMMY

CREEK FAULT

MTN THRUST FAULT

LARAMIE RIVER VALLEY LARAMIE MOUNTAINS

Jmsj

B B'

Quaternary deposits are not shown.

North Park Formation (Nn) is shown thicker than actual thickness.

3,000

4,000

2,000

1,000

0

METERS

3,000

2,000

1,000

0

METERS

Sea Level

4,000

YXu Kss

Kmv

Kn

Nn

Jmsj

Kn Kd

Pgl

Kbm

Prgu Pf

Pgl

Prgu

Pf

MCINTYRE CREEK FAULT

NORTH MIDDLE MTN

THRUST FAULT

GREEN RIDGE FAULT

NORTH MIDDLE MOUNTAIN

LARAMIE RIVER FAULT ZONE

?

GREEN

RIDGE

Jmsj

C C'

Quaternary deposits are not shown.

North Park Formation (Nn) is shown thicker than actual thickness.

3,000

2,000

1,000

0

METERS

3,000

2,000

1,000

0

METERS

Sea Level

?

?

?

Kp YXu YXu

c

Fault

breccia

r

Kn

v

Ngy

Kbm

Kbm

Kd

Jms Prgu

Prgu

b

CAMERON

PASS FAULT

Quaternary deposits are not shown.

 Projected base of Coalmont Formation (c)

MEDICINE BOW

MOUNTAINS

NORTH PARK NEVER SUMMER

MOUNTAINS

3,000

2,000

1,000

0

METERS

3,000

2,000

1,000

0

METERS

Sea Level

4,000 4,000

D D'

?

YXu

YXu

Pf

Phf Pi

Po

Pl

Jmsj Kd Kbm Kn wr Kpl

Pl Kd No/Na? Pi Jmsj

HALLIGANRESERVOIRFAULT

Table Mountain

CHEYENNE TABLELANDS

Fault

breccia

Block-glide

landslide

NORTH FORK CACHE LA FOOTHILL HOGBACKS

POUDRE RIVER VALLEY

Pi Po

Quaternary deposits are not shown.

No/Na? indicates combined unit Ogalalla (No) and Arikaree (Na?).

3,000

2,000

1,000

0

METERS

3,000

2,000

1,000

0

METERS

Sea Level

E E'

Kpl

YXu YXu

Kpu

Kpm

Pf

Kd

Kn

Jmsj

Kbm

Pi Po Pl Kpr Kph

Pf

Kbm

Ngy CACHE LA POUDRE PALEOCHANNEL

WEST LIVERMORE FAULT

LIVERMORE FAULTNORTH FORK FAULT

EAGLES

NEST LIVERMORE EMBAYMENT

FOOTHILL HOGBACKS

block-glide

landslide

DOUGLAS LAKE ANTICLINE

WELLINGTON ANTICLINE

Whittier Oil Field

COLORADO PIEDMONT

Quaternary deposits are not shown.

F F'

2,000

1,000

0

METERS

2,000

1,000

0

METERS

Sea Level

Kpl

YXu

Kpu

Kpm

Kpr

Pi

Jmsj

Kd Kn

Pl

Kph

Kbm

Po

Pf

Pi

Pf

Pf

FORT COLLINS ANTICLINE

FLETCHER HILL FAULT

BUCKHORN CREEK FAULT

Po Pi

HorsetoothMountain

FRONT FOOTHILL HOGBACKS COLORADO

FORT COLLINS

Quaternary deposits are not shown.

G RANGE PIEDMONT G'

3,000

2,000

1,000

0

METERS

3,000

2,000

1,000

0

METERS

Sea Level

Figure 4. A, Index map showing sources of geologic-map data used in compiling the Fort Collins 30'×60' quadrangle. For U.S. 

Geological Survey publications, report number, authorship, and date of publication are shown.

Photo looking south from the eastern foot of 

South Rawah Peak (just off frame to the right) 

in the Rawah Wilderness. Rockhole Lake is in 

the immediate foreground with Twin Crater 

Lakes behind. The prominent peak on left in 

the far background is Clark Peak (the highest 

point in the Medicine Bow Mountains and the 

map area). Note the large rock glacier (Qr) 

sloping east down to Rockhole Lake across 

the center of the view. All of the low ground 

was subjected to multiple cycles of middle to 

late Pleistocene glaciation with latest 

Pleistocene till of post-Pinedale age (Qtpp) 

preserved in the immediate foreground. The 

high ridges are all composed of Granite of the 

Rawah batholith (XgR).Photo taken by C.R. 

Ruleman on May 24, 2005.

Photo of tightly folded Proterozoic rocks of the volcanic source 

dominated terrain along Cornelius Creek at the southern edge of the 

Eaton Reservoir 7.5' quadrangle. Interlayered felsic gneiss (Xf) and 

hornblende gneiss and amphibolite (Xh) are quite typical within this 

terrain. Layering occurs from centimeter-scale through 

kilometer-scale and layers can be traced for significant distances. 

These are interpreted as layered felsic and mafic metavolcanic rocks. 

Peak metamorphism occurred during intrusion of the Routt Plutonic 

Suite locally dominated by the granite of the Rawah batholith (XgR) 

exposed south of this location. The folding shown here runs parallel 

to the local foliation orientation which trends roughly east-northeast. 

Photo taken by J.B. Workman on July, 26, 2006.

Figure 4. B, Index map of compilation responsibilities for new mapping in the Fort Collins 30'×60' quadrangle.

ROCKY MOUNTAIN

NATIONAL PARK

WYOMING

COLORADO

Eggers

JACKSON COUNTY

LARIMER COUNTY

LARIMER COUNTY LARIMER COUNTY

ALBANY COUNTY LARAMIE COUNTY

14

14

287

287

40°30'

106°

41°

105°

Teds Place

Bellvue

Laporte

Fort

Collins

Buckeye

Wellington

Kinikinik Rustic Idylwilde

Red Feather Lakes

Log Cabin

Stove

Prairie

Landing

Virginia

Dale

Glendevey

Stove

Prairie

ot enneyehC revneDot

ot nedlaW

to Laramie

Cameron

Pass

Base from U.S. Geological Survey digital data, 2010

Universal Transverse Mercator projection, zone 13N

North American Datum 1927

25

?

D U

D U D

U

D U

D

U

U D

DU

D U

D

U

D

U

U D

D

U

D

U

D

U

D

U

D U

D U D U

D U

D U

D U

D

U

D

U

D

U D

D U

U

D U

U D

U D

U D

D

U

D U

D U D D U D

U

D U

D U

D

U

D

U D U

D

U

D U

D U

D

U

D

U

D

U

U D

D

U

D

U

D

U

D

U

D U

D U

D

U

D

U D U

D

U

D U

D

U

D U D U

D

U

DU

D U

D

U

D U

CORNELIUS CREEK SHEAR ZONE

SHEEP CREEK FAULT ZONE

BULL MOUNTAIN FAULT

MCINTYRE CREEK FAULT

GREEN RIDGE

FAULT

PANHANDLE CREEK

RED FEATHER

ELKHORN CREEK

POUDRE RIVER SHEAR ZONE

SKIN GULCH SHEAR ZONE 

CAMERON PASS 

SHIPMAN PARK FAULT

BLUE LAKE

KELLY LAKE

FAULT

GRASSY PASS

FAULT

EAST JIMMY CREEK FAULT

SKIN GULCH SHEAR ZONE

ELEPHANT

MOUNTAIN

BOSTON PEAK

FAULT

FAULT ZONE

HALLIGAN RESERVOIR

FLETCHER HILL

STOVE PRAIRIE FAULT

BUCKHORN CREEK

THOMPSON

CANYON FAULT

LIVERMORE

NORTH LIVERMORE

WEST

LIVERMORE

DILKY RANCH FAULT

NORTH FORK

RIST CANYON

REDSTONE CREEK

REDSTONE CREEK

CAMPBELL

MOUNTAIN

ROUND

BUTTE

MILL CREEK

SHEAR ZONE

SHEAR ZONE

LAKES SHEAR ZONE

MOUNTAIN THRUST

NORTH MIDDLE

FAULT

FAULT

FAULT

FAULT

FAULT

FAULT

FAULT

FAULT

FAULT

FAULT

FAULT

FAULT

FAULT

BELLVUE

HEWLETT

FAULT

STINK CREEK

FAULT

BUCKHORN CREEK

FAULT

SHELL CREEK

FAULT

 FAULT

 FAULT 

FAULT 

0 2 4 6 KILOMETERS

0 2 4 6 MILES

Base from U.S. Geological Survey digital data, 2010

Universal Transverse Mercator projection, zone 13N

North American Datum 1927

COLORADO

WYOMING EXPLANATION

Fault—U indicates upthrown block; D downthrown;

 teeth on upper plate of thrust faults

Proterozoic fold axis

Laramide fold axis—Anticline

Exposed Proterozoic basement rocks

Laramide fold axis—Syncline

U

D

Figure 13. Map showing major structural elements of the Fort Collins 30'×60' quadrangle. Dark gray areas are Proterozoic crystalline basement rocks 

and light gray are Phanerozoic deposits. Major faults and shear zones are shown with names (FLT, fault) and inferred sense of offset (U, upthrown 

block; D, downthrown block; teeth on upper plate of thrust fault) where known. Proterozoic fold axes (red lines) are shown within crystalline basement 

rocks and Laramide folds (magenta lines; arrows indicate fold type) are shown within Phanerozoic rocks.

Livermore

CRAZY

MOUNTAIN

SAND CREEK

PASS

EATON

RESERVOIR

DIAMOND

PEAK

CHEROKEE

PARK

VIRGINIA

DALE

TABLE

MOUNTAIN

ROUND

BUTTE

GLENDEVEY DEADMAN SOUTH BALD

MOUNTAIN

RED FEATHER

LAKES

HAYSTACK

GULCH

LIVERMORE

MOUNTAIN

LIVERMORE BUCKEYE

RAWAH

LAKES

BOSTON

PEAK

KINIKINIK RUSTIC BIG NARROWS POUDRE

PARK

LAPORTE WELLINGTON

CLARK PEAK CHAMBERS

LAKE

COMANCHE

PEAK

PINGREE PARK CRYSTAL MOUNTAIN BUCKHORN

MOUNTAIN

HORSETOOTH

RESERVOIR

FORT COLLINS

Reconaissance mapping

by J.C. Cole

Reconaissance mapping

by K.S. Kellogg

Previous mapping

compiled by

K.S. Kellogg

Previous mapping

compiled by

J.B. Workman

Previous mapping

compiled by

J.B. Workman

Previous mapping

compiled by

J.B. Workman

Reconaissance mapping

by W.A. Braddock (USGS) Reconnaissance

mapping of

surficial deposits

by R.R. Shroba

(diagonal overprint

pattern)

Reconnaissance

mapping of

surficial deposits

by R.R. Shroba

(diagonal overprint

pattern)

Reconaissance

mapping

by J.B. Workman,

K.S. Kellogg,

W.A. Braddock,

and R.R. Shroba

40°30'

106°

41°

41°52'30"

41°45'

41°37'30"

105°52'30" 105°45' 105°37'30" 105°30' 105°22'30" 105°15' 105°07'30" 105°

OFR 81–578 

(Pearson and

others, 1981)

OFR 82–376

(Pearson and

others, 1982)

CRAZY

MOUNTAIN

SAND CREEK

PASS

EATON

RESERVOIR

DIAMOND

PEAK

CHEROKEE

PARK

VIRGINIA

DALE

TABLE

MOUNTAIN

ROUND

BUTTE

GLENDEVEY DEADMAN SOUTH BALD

MOUNTAIN

RED FEATHER

LAKES

HAYSTACK

GULCH

LIVERMORE

MOUNTAIN

LIVERMORE BUCKEYE

RAWAH

LAKES

BOSTON

PEAK

KINIKINIK RUSTIC BIG NARROWS POUDRE

PARK

LAPORTE WELLINGTON

CLARK PEAK CHAMBERS

LAKE

COMANCHE

PEAK

PINGREE PARK CRYSTAL MOUNTAIN BUCKHORN

MOUNTAIN

HORSETOOTH

RESERVOIR

FORT COLLINS

Burch, 1983

Camp, 1979

Walko, 1969

Griswold, 1980

I 1973

(Braddock and Cole, 1990)

I 855–G

(Colton, 1978)

I 1805

(Courtright and

Braddock, 1988)

T.G. Plymate and

others, 2005

SIM 3133

(Workman and

Braddock, 2010)

SIM 3029

(Workman, 2008)

GQ 1614

(Braddock and

others, 1989)

GQ 1615

(Eggler and

Braddock, 1988)

GQ 1617

(Braddock and

Connor, 1988)

GQ 1618

(Braddock, Wohlford,

and Connor, 1988)

GQ 1618

(Braddock, Connor,

Swann and

Wohlford, 1988)

GQ 1620

(Braddock, Abbott,

Connor,and

Swann, 1988)

GQ 1619

(Shaver and

others, 1988)

SIM 3010

(Kellogg, Ruleman

and others, 2008)

GQ 1622

(Nesse and

Braddock, 1989)

GQ 1623

(Braddock and

LaFountain, 1988) GQ 1624

(Braddock, O’Connor,

and Curtin, 1989)

GQ 1625

(Braddock, Calvert,

O’Connor, and

Swann, 1989)

GQ 1323

(Abbott, 1976)

GQ 1616

(Braddock, Eggler

and Courtright, 1989)

40°30'

106°

41°

41°52'30"

41°45'

41°37'30"

105°52'30" 105°45' 105°37'30" 105°30' 105°22'30" 105°15' 105°07'30" 105°

M

M

M

M

M

K

K

M

M

M

K

-A

-A

-A

-A

-A

K

M

M

K

K

K

K

-A

-A

K

S S

S

S

S

S

S

35

30

8 85 15

10

15

63

25

22

35

20

15

50

6

4 3 4

3

3

5

30

58

52 81

70 83

75

59 70

66

60

77

77

66

64

67

75

74 55

88

80

58

85

77

77

87

65 70

75

78

75

80

35

38

72

75

66 85

65

70

70

70

70

70

55

80

80 80 80

80

80 80

80

65

50

85

70 80

73

63 81

80 82 58

46

72

52

72

75

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85 76

63

58 65

58

58

56

76 80

67

64

73

61

35

37

71

72 74

70

61

62

75

80

80 85

87

80

55

80 

48 

45

73

60

60

44

88

68

75 85

72

74

70

70

60 65 79

80

69 74

32

43

69 78

56

56 44

45 46

41

49

43

68

46

81 85

67

54

75

80 75

15

25

15

15

30 33

30

30

35

35

20

20

5

15

25

15

25 25

38

25

35 15 20

40

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45

17

20

25

20

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40

40

22

25

40

40

40

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45

5

50

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70

70

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65

65 65 85

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50 50

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55

65

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35

45

40

50

50

60

80

55

55

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60

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68

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70

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86

70 70

60

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75

75 85

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80

60

60

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65

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80

65

70

70

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85

70

65

75

75

75 80

80

10

80

65

65

65

65

65

64

76

73

77

78

70

70 77

78

87

76

69

50

50

65

65

75 75

75

75

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65

78 50

50

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67

64

45

45

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70

70

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75

65

60

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35

45

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80

60

80

71

78

88

60

80

78

72 84

83

80 85

82

35

80

62

70

80

75

50

76

70

70

60

86

70 55

80

80

80

80

80

80

80

82 89

85

85

85

65

80

55

67

70

70

75

85 85 65

85

82

87

81 80

80

80

83

70 75

75

72

70

85

85

80

80

77

70

75

75

65

75

55

85

80 75

80

80

65

76

80

80

85

65

75

50

65

70

70

80

70

80

80

36

45

60

55

50

70

60

70 57

45

35

70

71

75 15

85

68

65

80

80

78

78

68

85

87

84

63

66

66

65

84 76

75

76 36

55

66

70

65 60

60

80

80

85

59

56 85

64

79

50 65 65 62 80

40

45

55

80

63

65

75

80 76 78

70

45

57

85

85

85

48

48

83

87

86 75

86

70 80

70

84

83

77

78

68

77

62

85

85

65 82

84

84

84

74

74

80

80

75

80

78

85

70

60 70

65

65

65

65

65

65

58

80

80

75

84

46

30

20

40

40

60

60 80 80 50

55

55

50 60

60

80

15 15

28

28

38

38

44 56

80

88

85

65

55

85

42

40

35

30

76

35

58

15

55

25

30

48

33

65

65

75

75

85

85

53

75

75

75

75

65

55

35

80

50

22

84

83

51

55

25 80

40

77 72

41 65 50

60

80

80

60

70

25

40

35

65

78 75

81

72

67

65

65 55

42

10

74

62 67 28 49

75

75

75

75

65

65

40

60

65

75

45

65

65

65

45

60

30

20

63

55

75 76 63 75 45

40

40

40

80

60

50

50 30

35

85

85

85

50

85

85

85

85

85

85 87

42

40

70

70

15 70

70

75

75

75

75

70

70

70

70

70

70

70

70

50

68

76

75

75

75 75

75

75

73 72

75 75

85

85

85

85

85

85

65

35 53

55

55

55

80 85

47

75

68

77

73 80

80

35

60

60

78

45

45

87

73

72

65

60

60

60

65

80

82

80

80

80

84

64

55

60

70

75

75

76

55

25

65

75

60

80

30

65

85

85

80

70

80

80

50

65

65

65

80

70

70

80

80

35

72

60 63

60

65

71 77

51 79

74

64 56

50

65

65

65

45

75

75

85

85

80

80

65

63

43

54

59 69

77

55

55

45

68 68

63

80

65

58 68

86

62

79

4

3

5

40

5

2

20

20

68

42

80 10

10

27

22

30

10

35

80 40 15

45

75

15 4

65

65

35

25

75

15

4

70

75

80

70

75

75

75

65

85 35

60 60

50 40

45

45

35

45

35

40

40

50

50

50

60 60

60

70

75

75

25

50

50

50

50

55

85

85

85

55

65

55

70

70

75

55

80

80

80

80

80

80

60

22

80

85

55

80

80

80

46

80

80

70

35

70

70

65

65

65

70

46

70 70

75

75

75

75

60

66

60

60

80

30

60

60

85

45

45

45

35

80

50

50 30

55 75

75

75

70

70

75

75

80

75

65

80

55

55

55

65

65

75

45

65

65 70

55

55

55

65

80

65

50

80

75

75

75

75

35

60

60

60

85

80

85

40

40

42

35

70 50

50

40 70

70

80

80

70

55

75

35

35 54

60

60

65

45

10

15

14

23

80

75 75

45

85 15

20

12

10

3 3

15

40

40

80

30

55

20

85

30

75

50

50

30

80 80

55

53

3

73

55

53

42

18

18 

24

53

28

60

72

72

67

66

74

78 67

24

23

23 

39 

21

8

16 

15

20

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87 71

71

43

55

33

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87

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72

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83

80

54 67 76

88

44

45 65

67

80 85

77

68 77

81

89

77

41

50

64

75 85 70

56

30

34

24

32 

70 

60

48

48

40

60

50

84

73

82

70 74 53

70

70

80

80

81

56

63

59

55

77

75

83

85

82

75

64

60

65

65

65

63

74

70

60

73

80

50

40

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50

70 64

60

58

80

80

55

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65

55

70

5 3

9

4

5

18

76

76

65

82

33

75

85

74

84 80

80

80 83 87

74

83

88

78

78

86

75

73

84

84

80

20

20

65

55 35

12

12

16 42

22

18

13

20

18

14 16

41

10 10

14

21

47 42 43

6

8

5 10 5 4

11

13

10

14

15

15

70

57

80

80

50

80

80 60 60

25 3

8

8

5

30

45

45

21

30

22

10

15

11

65

16

56

68 81

80

56

70

70

75

81

66

63

83 85

75

72

72

78

76 76

74

80 80

65

60

64

62

56

72 74

80

54

85

55

74

64

64

82

50

70

20

30

50

73

53

70

75

46

72 72

84 84

78

70

64

83

74

74

55

85

83

78

82

70

70

70

72

76

74

78

76

83

56

80

85

60

83

50

61

61 69

64

89

50

57

72

72

73

44

70

75

30 60

80

80 80

80

85

75

85

68

85 87

80

80

60

60

72

85

45

35

80

60

80

70

70

64

67

80

80

80

80

80

85

85

80

82

81

51

80

45 30

30

50

60

65 65

80

68

60

60

65

85

84

84 80

84

79 64 66

62 47

72

71

70

81

84

85 78

78

52

80

86

42

38 30

57

57

40

40

60 81 69

86

80

81 84

87 42

49

60

65

61

74 50

69

67

59

64

67

61

69

69

69

75

65

65

82 84

50

73 43

35

55

55

25

63

80

80 85

70

70

70

70 58

30

55

65

82

69

81 85

73

83

45

83

82

75

80 80

80

80

70

75

75 85

81

55

55

75

75

70

70

70

70

70

75

72

76 76

75 50

65

82

48

85

85

88

86

65

85

70

71

78

81 85

85

88

80

79

84 71

77

76

75

62 50

83

74 70

83

83

76

77

67 70

65

85

85

86 80

70

71 15 15

80 23 22 17

24

24

20

20

20

66

57

22

22

23

35

57

70

52 55

70

55 60

25

26

19

22

18

20

42

10

8

10

30

15

77

77

14

22 22 26

65

20

18

64

50

68 68

17

61

65 64 81

51 86

85

85

85

85

85

85

75

70

70

70

85

85

82

80

80

80

88

86

80

88

84

79

75

72

50

80

78

33

20

82

14 30

65

85

87

62

75

72 72

76

76

75

75 75

75

75

65 75

74

89

85

24

61

72

84

82

88

74

72 86

72

72

61

73 70

62

68

44

80

78

78

82 62

60

80

80

60

50

50

82

82

80

75

75

75

86

79

88

80

60

66

67

81

81

31 86

82

85

25

25

25

25

50

16 24

85

77

19

83

85

80

80

80 55

80

80

85 75

75

75

80 80

80

70

45

45

45

65

65

65

65

40

50 40

45

65 55

50

70

70

70

70 70

72

77 74

72 15

75

73

65

65

83

80

37

50

85

87

70

69

68

67

62

70

11

15

19

5

8

18

30

30

27 15

17

16

17

15

75

55

11

13

13

82

75 75

70

85

55

70

86

84

86 83

81

80

80

80

80

80 81

81

66

55

64

85

85

83

87

87

78

76

76

82

85 83

83

20

15

18

70

12

14

15

42

35 23

84

45

58 72

75

71

61

84

25

20

14

25

80

82 87

82

76

85

89

55 70

70

89

64 77

75

70

68

86

80

16 14

13

22

9

40

14

15

13

2

80

80

50 3

20

45 30 85

75

80 70

70

80

3

80

80

81

68

82

70

77

70

75

75

77 55

81

54

80

85

85

85

80

88 85

85

52

25

72

76

62 74

22

35 80

80

80

80

85

60

60

45

35

57

85 85 65

75

45

25 45 55

85

83

80

45

42

70

70

75 70

70

55 60

85

45 60

60

56

82

84

80 64

60

86

85 45

48

83

65

69

60

57

64

50

68

82

85

55

76

60

60

70

65

81

70 74

80

85

85

85

70

70

80 80

80 72

80

70

80

80

85

70

73

54 54

85

85

56 87

70 71

85

80

75

80

78

55

50

74

68

55

67

84

83 85

75

75

55

55

75

75

66

60

88

80

65

84

81

86

80

75

75

80

75

72 83

83

85

85

82

87

75

70

80

80

80 80

80

70

70

83

70

70 73

75

75

67

65

57

80

80

80

70

75

75

70

74

34

81

38

88

86 69 75

65

50

75

73

73

55

72

68 73

82

82

65

66

77 84

82

85

58

35 70 30

40

63

60

60

85

60

70

75

20

6

70

80

80

80

85

40

75

12

3

3

3

5

5

8

7

2

70

50

60

78

17

17

18

27

30 70

16

35 28

25

34 15 11

2

9

10

10

10

8

9

7

4

14

11

15

13

11

26

12

24 14

14 54

17

16

34

31

21

13

20 10

10

12

20

40

32

30

30

20

4

75

45

80

54

2

5

9

7

9

10

6

29

15

18

10

9

22

12

16

6

58

60

64

31

30 15 52

25

12

10

9

6

9

15

7

9

8

3

15

10

10

8

6

8

3 3

11

10

12

12

11

6

10

11

11

9

5

6

8

4

6

9 9

12

12

12 12

15

7

7

17 20

13

15

10

8

15

15

5

3

14

15

15

9

13 15

5

52

35

26

60

65

11

12

13

7

7

9

3

11

11

8

6

25

15

15 47

37

12

88 60

68

81

69 69

72

24

35

73

Ygao

Snowfields

Snowfields

Pc

Pc

Pf

Pf

Pc

Pc

Pi

Pi

Xcg

Pl

Po

Pl

Pl

rw

Ngy

iy

iy

iy

rw

r

b

YXp

b

r

s

s

b

r

v

v

v

r

DZk

ap

Xh

Xbq

Xb Xbq

Xbq

Xf

Xf

Xb

Xfl

Xf

Xf

Xf

Xd

Xf

Xb

Xb

Xf

Xf

YXp

YXp

Xf Xb

Xbh

Xh

Xh

Xb

Xh

Xb

Xb

XgR

XgR

Ygb

Xb

Xh

YXp

Xb

Xb

Xf

Xf

Xfl

af

Xf

Xf

Xgd

Xbg

Xf

Xf

Yg

YgLP

Yd

YXp

YXp

YXp

Xbk

Xbk

Xb

Qta

Qtp

Qtp Qta

Qr

Qva

Qva

Qtp

Qtp

Qc Qc

Qc

Qc

Qtp Qo

Qo

Qo

Qo

Qo

Qo

Qta

Qta

Qls

Qr

Qc

Qc

Qc

Qc

Jms Qta

Qc

Qr

Qta

Qc

Qta

Qac

Qva

Qva Xgd

Ygay

Xh

Xgd

YgH

YgH

YgH

YgH

YgLP

YgLP

YgLP

Xgd

Qc

Qva

Qva

Qc

Yge

dp

dp

Xgd

Xf

Xf

Xfl

Xfl

Xfl

XgR

Xgdp

XgR

XgR

XgR

XgR Xbh

Qta

Xh

Xh

Xbh

XgR

XgR

Ygb

Ygb

Xfl

Xf Xf

Xf

Xf

Xfl

Xfl

Xf

Xf

Xf Xb

Xf

Qta

Qva

Qva

Qta

Xb

Xb

Xh

Xb

Xh

Xb

Xbh

Xh

Xh

Xh

Xh

Xh

Xbg

Xbq

Xf

Xcg

Xf

Xcg

Xb

Xbq

Xbg

Xbq

Xbq

Xbp

Xh

Xh

Xh

XjT

Xh

Xbq

Xbk

Xh

YXp

Qc

Qc

Qc

Qc

Qva

Qva

Qva

Qva

Xh

Xh

(Dike filled

fault zone)

Qp

Qp

Nn

Nn

Nn

Ngy

go

Xh

r

r

Kn

Qp

Qgb

Kb

Kss

Kd Jm

Qac

Qf

Qsw

Qva

Qsc

Qsc

Kss

Qgp

Qls

Qva

Qc

Qsc

Qac

Qac

Qac

Qac

Qac

Qva

Qva

YgSH

Yghp

Yghp

Yghp

Ygao

Ygao

Xfl

Xfl

Xfl

Xfl

Xfl

Xfl

Xfl

Xbq

Xbq

Xbq

Xfb

Xbq

Xbq

Xbq

Xbq Xbq

Xf Xh

Xbq DZk

Xfb

Xfb

Xp

Xp

Xp

DZk

DZk

YgLC

Qc

Qva

Qva

Qc

Qp

Qp

Qp

Xb

Xb

XgR

XgR

XgR Qva

Qta Qva

Qva

Qva

Qva Qva

Qac

Xh

Xb

Xb

Qf

Qac

Qva

Qgp

Qc

Qc

Qc

Qc

Qc

Qc

Qls

Qgp

Qgp

Qtp

Qtp

Qtp

Qva

Qtp

Qtp

Qtp

c

c

iy

iy

c

iy

Qc

Qc

Qc

Qr

Qr

Qta

Xbh Kn

Kn

Kn

Xbh

Qac

Qac

Qls

Qtp

Qls

Qg

Qtp

Xh

Xb

Kb

Kd

Kd

Kd

Kn

Kb

Kb

Qgp

Kb

Kb

Jms

Jms

Kd

Kd

Kss Qgp Prgu

Qgp

Jms

Xf

Prgu

Prgu

Prgu

Jm

Jm

Qta

Kd

Qva

Qtp

Qtp

Qls

Qc

Qtp

Qgp

Qc

Qtp

Qtp

Qtp

Qtb

Qsw

Qac

Qac

Qf Kss

Qgb

Ygb

Xbh

Qp

Qp

Qva

YXp

DZk

DZk

Xb

Xp

Xbq

Xh

Xh

Qva

Qva

Qva

Qva

Xh

Xh

Xfb

Qva

YXp

YXp

YXp Yd

Xbq

YgLC

Xbq

Xfb

Xfb

Ngy

Ngy

Ngy

YgLC

YXp

Yd

Xh

Xh

Xh

Xh

Xh

Xh

Xh

Xh

Xf

Xf

Xf

Xb

Xf

Xf

Xbh

Xfl

Xb

af Xf

Xh

Xh

Xh

Xh

Qva

Xfl

YgLC

YgLCp

YgLCp

Xgd

YgLCe

YgLCe

YgLCe

YgLCp

YgLCe

YgLCe

YgLCe

YgLCe

Xb

Xb

Xfl

Qva

Qva

Qva

Qva

Qac

Qac

Xfl

XgR

Xb

Xb

Xh

Xh

Xh

Xh

Xh

Xh

Xfl Xb

Xh

Xbh

Xh

Qva

Xh

Xh

Xfl

Xfl

Xfl

Xfl

Yd

YgSH

YXp

Xbq

Xfb

Xfl

Yd YXp

Xfl

Xfl

Xfl

Xf

Xf

Xh Xfl

Xfl

Xfl

Xfl

Xbh

Xbh

Yd

Qsw

Qtp

Qta

Qf

Qgp

Qtp

Qc

Qc

Qtp

Qac

Qta

Qtpp

Qtpp

Qtpp

Qtpp

Qta

Qc

Qc

Xbh Xbh

Qgp

Qva

Qva

bs

s

s

Qls

Qgp

Qtp

Qac

Qc

Qc

Qf Qc

Qr

Qr

Qr

Qta

Qgb Qta

Qta

Qta

Qac

Qva

Qta

Qta

Yd

Qva

Qc

Qta

Qc

Qf

Qac

Qc

Qgp

Xbh

Xbh

Xbh

XgR

XgR

Ygay

XjT

Xh

Xbh

Xbh

Xbh

Xbh

XgR

Xh

Xbh

Xbh

Yd

Xgbh

Xb

Xfl

Xh

XgR

YXp

Qva

YXp

YXp

YgLC

YgSH

YgSH YgSH

Yg

Ygao

Qp

YgSH

YXp

Yd

DZk DZk

Pf DZk

Pf

Pf

wr

Jsj

wr

wr

Po

Po

Po

No

No

Na?

Na?

Pi

Pi

Pi

Pi

Pf

Pf

Qva

Qa

Qg

Qg

Qg

Qg

Na?

Kd

Kd

Kpl

Kpl

Kpl

Kpl

Jm

Kb

Kn

Kpl

Kd

Kd

Kd

Qls

Kpl

Kpl

Pf

Pf

Pf

Pf

Pf

Po

Pi

Pi

Pi pl

Xgd

Po

Kb

Pl

YXp

Pl

XjT

Xgd

YXp

pl Pf

Jsj

Jsj

pl

Pi

Pi

Po

Jm

Pl

Pl

Pl

Kpl

Kpu

Kpr

Kpu

Kpl

Kn

Kn

Kph

Kpm

Kb

Kn

Qc

Qc

Qc

Qc Qva

Qc

Qls

Qls

af

af

af

af

Qc

Qls

Kpl

Kb

Kb

Kb

Kpl

Kpl

Kpu

Kb

Pl

Yd

Yd Xh

Yd

Xbk

Xbk

Xbk

Xbk

Xgd

Xcg

Xgd

Xgd

Ygay

Yge

Xbq

Xbq Xbq

Xbq

Xbp

Xbg

Xbg

Xbq

Xbq

Xbq

Xbq

Xbq

Ygay

Yd Ygay

YXp

Yqd

Yqd

Yqd

YgLC

Yge

YXp

YXp

Qva

YXp

XjT

XjT

XjT

XjT

Xbk

Xgd

Yd

Xgd

pl XjT Po Pl

Pi

J^sj

Ngy

Xbq

Xbq

Xgd

Xgd

YXp

Xbk

Xbk

Xbk

Yd

Xbk

Xbp

Xbp

Xbq

Xh

Xbk

Yd

Xbk

Xbg

Xbq

Xbq

Ygay

Ygay

Xbq

Xbq

Xf

Kpl

Kph

Kph

Kpm

Kn

Kn

Kd

Jm

Jm

Jm

Jsj

Jsj

Kpr

Kpr

Kpr

Kpr

Kpr

Kpr

Kpu

Kpu

Kpu

Kpu

Kpu

Kpr

Kfh Kfh

Kpu

Kpm

Kpm

Kph

Kph

Nls

Kd Pl

pl

pl

pl

Jsj

Jsj

pl

Ngy

Pl

Po

Po

pl

pl

pl

Qa

Qg

Qa

Qa

Qa

Qa

Qg

Qva

Xf Xf

Xbq

YgLC

YgLC

YgLC

YgSH

YgSH

Yg

Yge

Yg

Yg

Yge Xbq

Xbq

Xcg

Xb

Xfl

YXP

Xb

Xcg

Xcg

Xcg

Xbh

Yg

Yg

Xbq

YXp

YXp

YXp

YXp

YXp

YXpYd

Ygay

YXp

YXp

Yd

YXp

Qac Qva Qc

Qc

Qf Qc

Qf

Yge

YXp

Yge

Yge

YXp

YXp

Qg

Xb

Xb

YXp

YXp

YXp

Xbq

Xbqh

Yge

Yg

Xh

Xh

Xh

Xb

Xb

Xf

Xf

Xf

Xf

Xbkh

Xbk

Xbk

Xbkh

Yg

YXp

Xbk

Ygay

Xf

Xf

Xf

Xh

Qc

Xfl

Xfl

Xfl

Xf

Xf

YXp

Xbk

Xfl

Xf

Xf

Qg

Qva

Yd

Xb Xfl

Qva

Qva

Yge

YXp

YXp

YXp

Yd

Yd

Yd

Yd

Qva

Qva

Qva

Xf

Qa

Qc

Qac

Qs

Qac

Qs

Qs

Qs

Qs

Qs

Qsw

Qsw

Qsw

Qv

Qsw

Qg

Qs

Qa

Qa

Qa

Qa

Qsw Qsw

Qls No

Qf

Qf

Qb

Qb

Qf

Qls

Qc

Qc

Qc

Qv

Qb

Qv

Qv

Qs

Qa

Qb

Qb

Qs

Qa

Qlo

Qs

Qc

Qs

Pl

Qlo

Qa

Qa

Qa

Qa

Qa

Qa

Qlo

Qlo

Qlo

Qa

Qb

Kpu

Kpm

Kpm

Kpu

Qa

Qb

Qb

Qs

Qb Qb

Qs

Qs

Qs

Qg

Qs

Qsw

Qsw

Qsw

Qac

Pi Pi

Pf

Pf

Ygbh

YgVo

YdV

YdV

Qva

YdV

YgVo

YgVi

YgVi

Ygbh

Ygao Yd

Qva

Qva

Qva

Qls

Qg

Yg

Yd

Yd

Yghp

Qac

Yd

Qva

Qc

Qp

Qp

Qc

Qac

Jm Jm

Qac

Qls

Qls

Qls

Qac

Qls

Qgp

Qgp

Qsc

Qls

Qc

Qc

Qva

Kd

Kb

Kb

Kd

Kd

Kd

Kmv

Qgb

Kn

Kn

Kb

Kss

Kss

Jm

Pgfsu Pgfsu

Pgsl

Jsj

Jsj

Jm

prgu

prgu

prgu

Jsj

Jsj

Jm

Pgfsu

Pgsl

Pgsl

prgu

prgu

Pf

Xfl

Xh

Nn

Nn

Ygsh

af

io

io

io

dp

Breccia

zone

Breccia zone

Breccia zone

?

?? ? ? ? ?

?

?

?

?

?

?

Unconformity

Unconformity

Unconformity

Unconformity

Unconformity

Unconformity

Unconformity

ARTIFICIAL-FILL

DEPOSIT

POST-LARAMIDE

SEDIMENTARY ROCKS

POST-LARAMIDE

VOLCANIC ROCKS

POST-LARAMIDE

INTRUSIVE

ROCKS

LARAMIDE

SEDIMENTARY ROCK

PRE-CENOZOIC SEDIMENTARY ROCKS

LARAMIDE INTRUSIVE ROCKS

ALLUVIAL DEPOSITS ALLUVIAL AND MASS-MOVEMENT

DEPOSITS

MASS-MOVEMENT

DEPOSITS

GLACIAL

DEPOSITS

ORGANIC

-RICH

DEPOSIT

EOLIAN

DEPOSIT

PALEOZOIC AND PROTEROZOIC 

INTRUSIVE ROCK

PROTEROZIC INTRUSIVE 

AND METAMORPHIC ROCKS

PALEOPROTEROZOIC

METAMORPHIC ROCKS

CORRELATION OF MAP UNITS

SURFICIAL DEPOSITS

Holocene

Pleistocene

Pliocene

Miocene

Oligocene

Eocene

Paleocene

Upper

Cretaceous

Lower

Cretaceous 

Upper

Permian 

Lower

Permian 

TERTIARY

QUATERNARY

CRETACEOUS

JURASSIC

TRIASSIC

PERMIAN

PENNSYLVANIAN

DEVONIAN(?) and

NEOPROTEROZOIC

PALEOPROTEROZOIC

MESOPROTEROZOIC

Paleogene

Neogene

MESOPROTEROZIC

INTRUSIVE ROCKS

MESOPROTEROZIC AND (OR)

PALEOPROTEROZOIC METAMORPHIC AND

INTRUSIVE ROCK

PALEOPROTEROZOIC

INTRUSIVE ROCKS

Na?

Nls Nn

af

Qva Qsw

Qgp

Qgb

Qa

Qb

Qv

Qs

Qf

Qg

Qc Qls

Qp

Qr

Qtpp

Qtp

Qtb

Qo

Qac Qsc Qta

No

Kfh

Kpr

Kpl

Kph

Kpm

Kmv

Kss

Kd

Kbm

Kn

Kpu

Jm Jms

Pgfsu

Pgsl

Pgl

Po

Pl

Pi

Pu

Qlo

DZk

Xb Xbq Xbk Xbp Xbg

Xbh Xbqh Xbkh

Xh

Xcg

Xf Xfl Xfb

Ygay

Ygb

Yg Yge YgLC YgLCe YgLCp YgLP

Ygao

Yd

YgVi YgVo YdV

YgSH

Yghp

Ygbh

Yqd

YgH

Xgd Xgdp Xgbh XgR

XjT

Xp

YXp

YXu

Ngy

wr s

bs

go

b

rw

v

rp iy

r

dp ap io

c

Jsj

Jmsj

Pl

Prgu

Pc

Pf

? ?

Kp

Qa

Qb

Qgp

Qva

Qsw

af

Qac

Qgb

Qp

Qc

Qls

Qf

Qsc

Qv

Qs

Qg

Qtb

Qo

Na?

Qlo

No

wr

Ngy

s

Nn

Nls

bs

go

Qta

Qtp

Qr

Qtpp

LIST OF MAP UNITS

[Due to the addition of a shaded relief base, colors on the List of Map Units and the 

Correlation of Map Units may not exactly match unit colors on the map]

SURFICIAL DEPOSITS

ARTIFICIAL-FILL DEPOSIT

Artifical fill (latest Holocene)

ALLUVIAL DEPOSITS

Valley-floor alluvium (Holocene)

Mountain-valley alluvium (Holocene and late Pleistocene)

Sheetwash alluvium (Holocene and late Pleistocene)

Broadway alluvium (late Pleistocene)

Terrace alluvium of Pinedale age (late Pleistocene)

Terrace alluvium of Bull Lake age (late and middle Pleistocene)

Gravelly stream alluvium (late and middle Pleistocene)

Slocum Alluvium (middle Pleistocene)

Verdos Alluvium (middle Pleistocene)

ALLUVIAL AND MASS-MOVEMENT DEPOSITS

Alluvium and colluvium, undivided (Holocene to middle? Pleistocene)

Sheetwash alluvium and colluvium, undivided (Holocene to middle?

Pleistocene)

Fan deposits (Holocene and late Pleistocene)

Pediment deposits (late and middle Pleistocene)

MASS-MOVEMENT DEPOSITS

Colluvium (Holocene to middle? Pleistocene)

Landslide deposits (Holocene to middle? Pleistocene)

Talus deposits (Holocene to middle? Pleistocene)

GLACIAL DEPOSITS

Rock-glacier deposits (Holocene and latest Pleistocene)

Till of post-Pinedale age (latest Pleistocene)

Till of Pinedale age (late Pleistocene)

Till of Bull Lake age (late and middle Pleistocene)

ORGANIC-RICH DEPOSIT

Organic-rich sediment (Holocene and latest Pleistocene)

EOLIAN DEPOSIT

Loess (late and late middle? Pleistocene)

POST-LARAMIDE SEDIMENTARY ROCKS

Ogallala Formation (lowermost Pliocene? to middle Miocene)

Arikaree(?) Formation (Miocene)

Landslide debris deposits (lower Miocene or Oligocene)

North Park Formation (Miocene and upper Oligocene?)

Younger high-level fluvial gravel (Miocene? and Oligocene)

White River Group, undivided (lower Oligocene and upper Eocene)

Lower Oligocene Brule Formation of upper part of White River Group

Upper Eocene Chadron Formation of lower part of White River Group

Sedimentary rocks, undivided (Oligocene and Eocene?)

Tuffaceous sandstone and basalt (Oligocene)

Older high-level fluvial gravel (Oligocene)

POST-LARAMIDE VOLCANIC ROCKS

Rhyolite tuff (upper Oligocene)

Rhyolite welded tuff (upper Oligocene)

Volcanic rocks, undivided (Oligocene)

Basalt (Oligocene)

POST-LARAMIDE INTRUSIVE ROCKS

Rhyolite porphyry and felsite (Oligocene)

Younger intrusive rocks, undivided (Oligocene)

LARAMIDE INTRUSIVE ROCKS

Dacite porphyry (Eocene)

Andesite porphyry (Eocene)

Older intrusive rocks, undivided (Eocene)

LARAMIDE SEDIMENTARY ROCK

Coalmont Formation (Eocene and Paleocene)

PRE-CENOZOIC SEDIMENTARY ROCKS

Fox Hills Sandstone (Upper Cretaceous)

Pierre Shale, undivided (Upper Cretaceous)—On cross section D–D' only

Upper shale member

Richard Sandstone Member, Larimer Sandstone Member, Rocky Ridge 

Sandstone Member and two intervening unnamed shale members

Middle shale member

Hygiene Sandstone Member

Lower shale member

Mesaverde Formation (Upper Cretaceous)

Steele Shale (Upper Cretaceous)

Niobrara Formation (Upper Cretaceous)

Benton Group (Upper and Lower Cretaceous)

Dakota Group (Lower Cretaceous)

Morrison Formation (Upper Jurassic)

Morrison Formation (Upper Jurassic) and Sundance Formation (Upper 

and Middle Jurassic), undivided

Morrison (Upper Jurassic), Sundance (Upper and Middle Jurassic), and 

Jelm (Upper Triassic) Formations, undivided— Shown in cross 

sections only

Sundance (Upper and Middle Jurassic) and Jelm (Upper Triassic) 

Formations, undivided

Lykins Formation (Lower Triassic and Upper Permian)

Lyons Sandstone (Lower Permian)

Lyons Sandstone and Owl Canyon and Ingleside Formations, undivided 

(Lower Permian)

Owl Canyon Formation (Lower Permian)

Ingleside Formation (Lower Permian)

Red Peak Formation (Lower Triassic) and upper part of Goose Egg 

Formation (Lower Triassic and Upper Permian), undivided

Lower part of Goose Egg Formation (Upper and Lower Permian)— 

Shown on cross sections only

Forelle Limestone Member (Upper Permian) and upper part of 

Satanka Shale Member (Upper and Lower Permian), undivided

Lower part of Satanka Shale Member (Lower Permian)

Casper Formation (Lower Permian to Middle Pennsylvanian)

Fountain Formation (Lower Permian to Lower Pennsylvanian)

PALEOZOIC AND PROTEROZOIC INTRUSIVE ROCK

Kimberlite (Devonian? and Neoproterozoic)

Kbm

Kd

Pgsl

Pgfsu

Pgl

Prgu

Pl

Pu

Po

Pi

Pc

Pl

Jm

Jsj

Kn

Jms

Jmsj

Pf

PROTEROZOIC INTRUSIVE

AND METAMORPHIC ROCKS

MESOPROTEROZOIC INTRUSIVE ROCKS

Gabbro of the Iron dike

Younger aplite dikes and plugs

Biotite granite

Equigranular biotite granite

Granite of Log Cabin batholith

Granite of Log Cabin batholith, undivided

Equigranular granite of Log Cabin batholith

Porphyritic granite of Log Cabin batholith

Granite of Longs Peak

Mafic dikes and plugs

Older aplite dikes and plugs

Virginia Dale ring-dike complex

Inner cap rock monzogranite of the Virginia Dale ring-dike complex

Outer cap rock monzogranite of the Virginia Dale ring-dike complex

Dioritic and hybrid rocks of the Virginia Dale ring-dike complex

Sherman Granite

Hornblende granite porphyry

Hornblende gabbro

Granite of Hagues Peak

Quartz diorite

MESOPROTEROZOIC AND (OR) PALEOPROTEROZOIC

INTRUSIVE AND METAMORPHIC ROCK

Pegmatite

Undivided intrusive and metamorphic rocks—Cross sections only

PALEOPROTEROZOIC INTRUSIVE ROCKS

Granodiorite

Porphyritic granodiorite

Hornblende gabbro

Granite of the Rawah batholith

Trondhjemite of Thompson Canyon

Gneissic pegmatite

PALEOPROTEROZOIC METAMORPHIC ROCKS

Biotite schist and gneiss

Quartzofeldspathic mica schist

Knotted mica schist

Porphyroblastic biotite schist

Granoblastic quartzofeldspathic biotite gneiss

Biotite gneiss and hornblende gneiss, undivided

Quartzofeldspathic mica schist and hornblende gneiss, undivided

Knotted mica schist and hornblende gneiss, undivided

Hornblende gneiss and amphibolite

Calc-silicate gneiss

Felsic gneiss

Leucocratic felsic gneiss

Biotite felsic gneiss

YXu

YXp

Xgdp

Xgd

XgR

Xgbh

Xp

XjT

Xbq

Xb

Xbp

Xbk

Xbh

Xbg

Xbkh

Xbqh

Xcg

Xh

Xfl

Xf

Xfb

Yge

Yg

Ygay

YgLC

Ygb

DZk

YgLP

YgLCp

YgLCe

Yd

YgVo

YgVi

YgSH

YdV

Ygbh

Yghp

Yqd

YgH

Ygao

r

rw

v

b

c

ap

io

iy

rp

dp

Kph

Kpl

Kmv

Kss

Kpr

Kpm

Kfh

Kp

Kpu

S

-A

K

M

3

80

56

EXPLANATION

Contact—Dotted where projected from surface on cross section

Fault—Dashed where approximately located, dotted where concealed. Dotted 

where projected from surface on cross section. Queried where existence 

or identity is questionable

Low-angle normal fault—Dashed where location approximate, dotted where 

concealed. Half-circles on downthrown block

Thrust fault—Dashed where approximately located, dotted where concealed. 

Teeth on hanging wall

Joint—Location approximate

Anticline—Arrows show direction of dip

Overturned anticline—Beds on one limb are overturned; arrows show dip 

direction of limbs

Antiform—In Proterozoic rocks. Arrows show direction of dip

Monocline—Arrow shows direction of dip

Monocline, anticlinal bend—Arrows show direction of dip; shorter arrow on 

steeper limb

Monocline, synclinal bend—Arrows show direction of dip; shorter arrow on 

steeper limb

Syncline—Arrows show direction of dip

Overturned syncline—Beds on one limb are overturned; arrows show dip 

direction of limbs

Synform—In Proterozoic rocks. Arrows show direction of dip

Metamorphic reaction isograd lines—Boundary of a metamorphic zone 

representing the first appearance (in) or disappearance (out) of a 

metamorphic index mineral

Sillimanite in

Andalucite, cordierite, and garnet out

Potassium feldspar in, lepidoblastic muscovite out

Migmatite in

Fluvial terrace scarp—Hachures point down scarp

Rocky Mountain National Park boundary

Key Beds

Rhyolite welded tuff (rw)

Lyons Sandstone (Pl)

Ingleside Formation (Pi)

Casper Formation (Pc)

PLANAR POINT FEATURES

Bedding and foliation

Horizontal bedding

Inclined bedding—Showing strike and dip

Inclined bedding—Showing approximate strike and direction of dip

Vertical bedding—Showing strike

Overturned bedding—Showing strike and dip

Inclined foliation—Showing strike and dip

Vertical foliation—Showing strike

AREAL FEATURES

Glacier or permanent snowfield

Water body

Boundary of block-glide landslide—Dashed where approximately located; 

dotted where concealed. Glide mass area is represented by a “broken 

block” pattern and coherent stratigraphic units are shown within the glide 

mass where present. Hachures point towards glide mass area

Breccia zone—Dashed where location is approximate

Increasing

Metamorphic Grade

1

1

0

0

KILOMETERS 1 2 3 4 65 87 109 11 12 13 14 15 16 17 18 19 2 0

MILES 1 2 3 4 5 6 7 8 9 10 11 12 13

1 000

5 000

0

0

 5 000 10 000 15 000 20 000 METERS

10 000 20 000 30 000 40 000 50 000 60 000 70 000 FEET

SCALE 1:100 000

1 CENTIMETER ON THE MAP

REPRESENTS 1 KILOMETER ON THE GROUND

CONTOUR INTERVAL 50 METERS

SUPPLEMENTARY CONTOUR INTERVAL 25 METERS

NATIONAL GEODETIC VERTICAL DATUM OF 1929

Base from U.S. Geological Survey Fort Collins, Colorado 100,000-scale map, 1983

Universal Transverse Mercator projection and 10,000-meter grid, zone 13. 

25,000-foot grid ticks based on Colorado coordinate system, north zone

1927 North American Datum of 1927 (NAD 27). To place on predicted North 

American Datum 1983, move the projection lines 6 meters north and 48 meters east

Rocky Mountain National Park boundary accessed on Dec. 20, 2017 at 

https://viewer.nationalmap.gov/launch/

There may be private inholdings within the boundaries of the National or State 

reservations shown on this map 

This map is not a legal document. Public lands are subject to change and leasing 

and may have access restrictions; check with appropriate offices. Obtain permission 

before entering private lands

APPROXIMATE MEAN DECLINATION

AT CENTER OF MAP, 2018

DECLINATION RANGE 8.2 TO 8.8 IN THE MAP AREA TRUE NORTH

MAGNETIC NORTH

81⁄2°

COLORADO

MAP LOCATION

Fort Collins

30'x60' quadrangle

A

B

A'

B'

C'

C

D D'

E

E'

F

F'

G'

G

Geologic Map of the Fort Collins 30'×60' Quadrangle, Larimer and Jackson Counties, Colorado, and Albany and Laramie Counties, Wyoming

By

Jeremiah B. Workman, James C. Cole, Ralph R. Shroba, Karl S. Kellogg, and Wayne R. Premo

2018

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 may 

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

items must be secured from the copyright owner.

For more information concerning the research in this report, contact the 

Center Director, USGS Geosciences and Environmental Change Science Center

Box 25046, Mail Stop 980

Denver, CO 80225

(303) 236-5344

Or visit the Geosciences and Environmental Change Science Center website at

https://www.usgs.gov/centers/gecsc

To learn about the USGS and its information products visit

http://www.usgs.gov/ 

1-888-ASK-USGS

For product and ordering information visit:

http://store.usgs.gov/

Suggested citation: Workman, J.B., Cole, J.C., Stroba, R.R., Kellogg, K.S., and Premo, W.R., 

2018, Geologic map of the Fort Collins 30'×60' quadrangle, Larimer and Jackson Counties, 

Colorado, and Albany and Laramie Counties, Wyoming: U.S. Geological Survey Scientific

Investigations Map 3399, pamphlet 83 p., 1 sheet, scale 1:100,000,

https://doi.org/10.3133/sim3399/.

ISSN 2329-132X (online)

https://doi.org/10.3133/sim3399

This map or plate is offered as an online-only, digital publication. Users should be aware that, 

because of differences in rendering processes and pixel resolution, some slight distortion of 

scale may occur when viewing it on a computer screen or when printing it on an electronic 

plotter, even when it is viewed or printed at its intended publication scale.

Selected Conversion Factors

Multiply By To obtain

Length

centimeter (cm) 0.3937 inch 

meter (m) 3.281 foot (ft) 

kilometer (km) 0.6214 mile (mi)

Area

square kilometer (km2

) 0.3861 square mile (mi2)

Divisions of Quaternary, Neogene, and Paleogene time

used in this report1

Period or

subperiod

Epoch Age

Quaternary

Holocene 0–11.5 ka

late 11.5–132 ka

Pleistocene middle 132–788 ka

early 788 ka–2.588 Ma

Neogene

Pliocene 2.588–5.332 Ma

Miocene 5.332–23.03 Ma

Oligocene 23.03–33.9 Ma

Paleogene Eocene 33.9–55.8 Ma

Paleocene 55.8–65.5 Ma

1

Ages of time boundaries are those of the U.S. Geological Survey Geologic Names 

Committee (2010) except those for the late-middle Pleistocene boundary and middleearly Pleistocene boundary, which are those of Richmond and Fullerton (1986). Ages 

are expressed in ka for kilo-annum (thousand years) and Ma for mega-annum 

(million years).

International System of Units to U.S. customary units

Multiply By To obtain

Length

inch (in) 2.54 centimeter (cm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

acre 4,047 square meter (m2

)

Altitude, as used in this report, refers to distance above sea level.

U.S. customary units to International System of Units

This map compilation and synthesis integrates geologic mapping 

and various topical studies carried out between 1960 and 1990 

under the U.S. Geological Survey (USGS) study of the northeastern 

Front Range, geologic mapping of Rocky Mountain National Park, 

and reconnaissance geologic mapping in wilderness areas. 

Authors of this report carried out detailed geologic mapping and 

reconnaissance in previously unmapped areas of the quadrangle. 

This publication further draws on topical studies in geology, 

hydrology, and geomorphology by numerous investigators from 

Federal, State, and local agencies, as well as university research 

published through the years.

Digital cartography and database by J.B. Workman

Digital topographic base prepared by T.R. Brandt

Publishing support provided by Denver Publishing Service Center

Edit and digital layout by L.J. Binder

Manuscript approved for publication February 22, 2018

Digital files available at https://doi.org/10.3133/sim3399

ScienceBase data release GIS and other files that support this report are available at

https://doi.org/10.5066/F7G44PHV

U.S. Department of the Interior

U.S. Geological Survey

ROCKY MOUNTAIN

NATIONAL PARK

Scientific Investigations Map 3399

Pamphlet accompanies map