afQfp

Qty

Qtm

Qto

Qba

Qtt

Qfy Qac

Qp

Qc Qsw Qsw

Qlo

Qls Qd

Qdo

Qlo

QloQty

Qlo Qlo Qlo Qlo QloQtm Qd Qtt Qp Qtt

Qp

Tw

Tws Twss

Twm

TwaTwav

Twal

Kmv

Kwf

Ki

Kwfu

Kwfl

Kir

Kicc

Kmu

?

??

?

?

?

?

Kmvb

?

?

?

Qg

Alluvial DepositsAlluvial and

Colluvial Deposits Colluvial Deposits Eolian DepositsArtificial

Fill Deposits

CORRELATION OF MAP UNITS

QloQto

Holocene

Pleistocene

UpperCretaceous

Paleocene

Eocene

QUATERNARY

TERTIARY

CRETACEOUS

MISCELLANEOUS FIELD STUDIES MAP MF - 2331Version 1.0

Pamphlet accompanies map

U.S DEPARTMENT OF THE INTERIORU.S. GEOLOGICAL SURVEY

Surficial geology was mapped by Ralph Shroba in 1992-1994 and byRobert Scott in 1996. Anne Egger provided field assistance in 1996.Digital compilation was begun by Heidi Torrelday in 1996, continuedby Robert Scott, Michael Helbraun, and Elijah Kempton in 1999. Digital Cartography by Theodore Brandt was completed in 2000.

Artificial fill (latest Holocene)

Flood-plain and stream-channel deposits (Holocene and late Pleistocene)

Younger terrace alluvium (late Pleistocene)

Intermediate terrace alluvium (late Pleistocene)

Older terrace alluvium (late middle Pleistocene)

Basaltic alluvium (late middle Pleistocene)

Oldest terrace alluvium (middle Pleistocene)

Younger fan-alluvium and debris-flow deposits (Holocene and latest Pleistocene)

Alluvium and colluvium, undivided (Holocene and late Pleistocene)

Pediment deposits (middle Pleistocene)

Colluvium, undivided (Holocene to middle? Pleistocene)

Sheetwash deposits (Holocene and late Pleistocene)

Sheetwash deposits over loess

Landslide deposits (Holocene to middle? Pleistocene)

Debris-flow deposits (Holocene? to middle? Pleistocene)

Older debris-flow deposits (early? Pleistocene)

Loess (late and middle? Pleistocene)

Loess over younger terrace alluvium

Loess over older terrace alluvium

Loess over oldest terrace alluvium

Loess over debris-flow deposits

Loess over pediment deposits

Loess over oldest terrace alluvium over pediment deposits

Wasatch Formation (in cross section only) (Eocene to Paleocene)

Shire Member (Eocene)

Sandstone unit

Molina Member (Eocene)

Atwell Gulch Member (in cross section only) (Paleocene)

Volcaniclastic-rich unit

Lower unit

Mesaverde Group (in cross section only) (Upper Cretaceous)

Williams Fork Formation

Upper unnamed sandstone unit

Lower unnamed sandstone unit

Iles Formation

Rollins Sandstone Member

Cozzette Sandstone and Corcoran Sandstone Members, undivided

Baked zone in the Mesaverde Group

Mancos Shale, Upper member (Upper Cretaceous)

Gravelly alluvium (late and middle Pleistocene)

LIST OF MAP UNITS

af

Qfp

Qty

Qtm

Qto

Qba

Qtt

Qfy

Qac

Qp

Qc

Qsw

QswQlo

Qls

Qd

Qdo

Qlo

QtyQlo

Qlo

Qlo

Qlo

Qlo

Qto

Qd

Qtt

Qp

Tw

Tws

Twss

Twm

Twa

Twav

Twal

Kmv

Kwf

Kwfu

Kwfl

Ki

Kir

Kicc

Kmvb

Kmu

Qg

QloQttQp

Loess over intermediate terrace alluviumQtmQlo

ARTIFICIAL-FILL DEPOSITS

ALLUVIAL DEPOSITS

ALLUVIAL AND COLLUVIAL DEPOSITS

COLLUVIAL DEPOSITS

EOLIAN DEPOSITS

BEDROCK UNITS

SCALE 1: 24 000

CONTOUR INTERVAL 40 FEETDOTTED LINES REPRESENT 20-FOOT CONTOURS

NATIONAL GEODETIC VERTICAL DATUM OF 1929

COLORADO

QUADRANGLE LOCATION

1987 MAGNETIC DECLINATIONAT CENTER OF SHEET

TRU

E N

OR

TH

MA

GN

ETIC

NO

RTH

12 ˚

1 MILE1 1/ 2 0

7000 FEET0 2000 3000 4000 5000 6000

.5 1 KILOMETER1 0

1/2

Qsw QswQsw

Qsw/Qlo

Qsw Qsw QswQc QswQlo/Qto

Qlo

Qlo/Qty

Qfpaf Qfy Qls

QtoQlo Qc Qc

QcQsw

Qlo/QpQac Qac Qlo/Qp

Qlo/QpQc

QlsQd

Qlo/QpQsw

Qlo/Qtm

Qsw QswQlo/Qp Qfp

TwTw

Kmv

Kmu

Top of Rollins Sandstone Member, Iles Formation

Top of Cozzette Sandstone Member, Iles Formation

Top of Corcoran Sandstone Member, Iles Formation

Tws

Twss

Twm

Twa

Twav

Twal

Kmv

Kmu

Kwf

Ki

Kicc

KirKmvb

KwflKwfu

Kmvb

Kmu

Pre-Kmu strata

Qsw

Qls

Tws

Twm

Twav KwfKir

Ki

Kicc

Kmu

8230 TD

AS

2

1

0

Koch

Exp

lor

Rifle

syn

cline

Colo

rado

Rive

r

Colo

rado

Rive

r NA'

2

1

0

Grand Hogback

S NB'B

Landslide

Grand HogbackOverturned strata

2

1 1

2

KILOMETERS KILOMETERS

KILOMETERSKILOMETERS

GEOLOGIC MAP OF THE SILT QUADRANGLE, GARFIELD COUNTY, COLORADOBy

Ralph R. Shroba and Robert B. Scott

2001

Contact--Solid where definite, dashed on map where

Limit of overturned strata

Syncline axial trace--Solid arrow shows direction of plunge

Strike and dip of bed

Horizontal

Overturned

Inclined

and total depth (TD) in feet

Dry hole--Showing name of drilling company

Gas well--Showing name of drilling company

and total depth (TD) in feet

Adit

Koch Explor8230 TD

Carter andCarter6147 TD

74

65

approximately located, dashed in cross section toshow stratal attitudes at depth

Any use of trade names in this publication is fordescriptive purposes only and does not implyendorsement by the U.S. Government.

For sale by U.S. Geological Survey Information ServicesBox 25286, Federal Center, Denver, CO 80225

This map was produced on request, directly fromdigital files, on an electronic plotter. It is also availableas a PDF file at http://greenwood.cr.usgs.gov

Base from U.S. Geological Survey, 1987

Polyconic projection, 1927 North American Datum

Qc

Qc

Qlo

Qlo

Qc

Qc

Qc

Qc

Qsw Qsw

Qsw

Tws

Tws

Qc Tws

Qdo

Qls

Qsw

Qlo

Qswaf

Qlo

Qsw

Qc

Qc

Tws

Qfy

Qto

Qtoaf

Qfy

Qsw

Qsw

Qc

Qls

Qc

Tws

Qsw

Qsw

Tws

Qacaf

Qfp

Qto

Tws

TwsQfp

Tws

afTws

Qc

Qac

Qsw

Qlo/Qto

Qlo/Qtt

Qtt

TwsQty

Qtyaf

Qto

Qc

Qac

Qfp

Tws

Qls

Tws

Qty

Qc

Qac

Qtyaf

Qty

Tws

Qsw/Qlo

Qlo

Qc

Qlo/Qto

Tws

Qty

Qsw

Qsw/Qlo

Tws

Tws

Tws

Qsw

Qsw

Qsw

Qsw

Qba

Qc

QcQc

Qsw

Qc

QswQlo

Qsw/Qlo

Qsw

Qlo

Qsw/Qlo

QtyQty

Qac

Qc

Qc

Qfy Qsw

Qc

TwsQto

Qba

Qba

Qsw

Qfy

Tws

Qc

Qc

Qac

TwsQc

af

Tws

Qfy

Qsw

Qsw

Qc

Qfy

Qty

af

afTws

af

Tws

Qsw/Qlo

QcTws

af

Tws

af

QcTws

Tws

Qto

Qc

Qty

Qba

Qsw

Qty

Qsw

Qac

Qty

Qc

Qc

Qsw

Qsw

Qc

QloQtt

Qsw/Qlo

Qsw/Qlo Tws

Tws

Qlo

af

af

QcQsw

Qc

Qc

QswQc

Qtt

Qsw

Qsw

Qsw

Qsw

Tws

Qac

Qsw

Tws

Qsw/Qlo

Qsw

Tws

Qc

Qsw

Qac

Qlo

Qsw/Qlo

Qsw

Qc

Qc

QcQsw/Qlo

QswQcQc

Qtt

Qsw

Tws

Tws

TwsQsw

Tws

Qsw/Qlo

Qsw

Qsw

Qlo

Qsw

Qsw

Qsw

Qsw

af

Tws

Tws

QcQc

Qtt

QttQsw

Qtt

Qsw/Qlo

Qtt

Qc

Qlo

Qtt

Tws

Qc

Qlo/Qtt Qsw

Qlo/QtoQlo

Qlo/Qty

Qc

Tws

Qtt

Tws

Qlo

Qsw/Qlo

Tws

TwsQsw

Qlo

Qlo

Qsw

Qc

TwsQtt

Qsw/Qlo

Qsw

af

Qlo/Qto

Qlo/Qp

Qlo/Qtt

Qac

Qsw

Qsw

Qc

Qsw

Qsw

QfyQfy

Qsw

Qsw

Qsw

Tws

Qc

Qp

Qc

Qp

Qc

Tws

Tws

Tws

Qc

Qc

Qlo/QpQlo/Qp

Qsw

TwsTws

Tws

Qg

Qlo

Tws

Tws

Qlo

Qsw

Qac

Tws

Tws

Tws

Tws

Qc

Qsw

Qsw

Qfy

Qty

Qsw

af

Qto

Qto

Qfy

Qto Qc

Qac

Qlo/Qto

Qlo/Qty

Qlo/Qto

Qlo/Qto

af

Tws

Qsw

Tws

Qtt

Tws

QswQac

Tws

Qc

Qc

Tws

Qlo/Qp

Qlo/Qp

Qsw

Qc

Qc

Qsw

Qlo/Qp

Qsw

Tws

TwsQsw

af

Qac

Qlo

Qc

QpQlo

Qc

Qsw

Qlo

Qc

Qc

Tws

Tws

Qsw

Qc

Qac

Tws

Tws

Qsw

Qsw

Qsw/Qlo

Qlo

QcQc

Qc

Qls

QlsQls

Qc

Qc

Qc

Qac

Qac

Tws

Tws

Twss

Twss

Twss

Qlo/Qp Qlo/Qp

Tws

Qlo/Qp

Qc

Twm

Twm

Twav

Twav

Twav

Qc

Qc

Qsw

Qls

Qc

Qac

Qc

Qsw

Qd

Twm

Twm

Twav

Twm

Twss

Qsw

Qc

TwsQsw

Qd

Qc

Twss

Kwf

Qac

Qsw

Qsw

Tws

QdQc

Qc

Qsw

Qls

QfyQsw

Qac Qlo/Qp

Qp

Qac

Qg

Qg

Qc

Tws

Qlo/Qp

Qc

Qc

Qc

Qsw

Qsw

Qd

QacTwm

Twm

Qlo/Qp

Tws

Qc

Qfy

Qc

Qls

Qc

Qc

Twav

Twav Qc

Twav

Twal

Twal

Twav

Qc

Twal

Twal

Twav

Qc

Qba

Qfy

Qfy

af

Twal

Qc

Qc

Qsw

Tws

Kwf

Twav

Twal

Qc

Twm

Twm

Twm Twm

Tws

Tws

Qlo/Qd

Qlo/Qd

Tws

Tws

Tws

Qlo/Qp

Qlo/QpTwss

Qlo/Qto

Qlo/Qto

Qlo/Qto

Qc

Tws

Tws

Qc

Qac

Qto

Qto Qlo

Qlo

Qlo/QpQlo

Qto

Qto

Qlo/Qtt

Twss

Qfy

Qlo/Qp

Qlo/Qp

Qsw

QcQp

Qsw

Tws

KirQac

Qac

Qc

Ki

Qc

QcQc

Kmvb

Kwf

Kwf

QswKmu

Kmu

Qc

af

Qc

Qc Qc

Kicc

Kicc

Qc

Kir

Kwf

Qsw

Qac

Qsw

Qc Qls

Qlo/Qp

Qc

Qac

Qls

Qac

Kmu

Kmu

Qfp

Qls

QswKmu

Qlo/Qp

Kmu

Kmu

Kmu

af

Kmu

Qc

Qsw

Kmu

Kicc

Kicc

Ki

KirKmvb

Kmvb

Qc

Kwf

Kmvb

Kmvb Kwf

Qc

Qsw

Kwf

Kwf

Twav

Qls

Twm

Qls Twav

Kwf

Kwf

Qc

Qsw

Tws

Tws

Qto

Qsw

Qfy

Qac

Qlo/Qp

Tws

Twav

afTws

Qlo/Qtt

QttQsw

QcafQty

Qac

Ki

Ki

Qlo/Qp

Ki

Qp

Qsw

Tws

Qc

Qsw/Qlo

Qsw/Qlo

Qlo / Qto

Qac

Qac

Kmu

Qlo/Qtt/Qp

Qlo

Qlo/Qp

Kwfu

Kwfl

Kwf

Kwfl

Kmvb

Kir

Kmvb

Kwfl

Ki

Kicc

Ki

Qlo/Qty

Qlo/Qto

Tws

Qp

Qac

Tws

Twm

Qlo/Qp

Qlo

Qsw/Qlo

QcTwm

Kwf

af

Kmu Kmu Kmu

Kmu

Qac

QacQac

Kmvb

Qsw

Qsw

Kmu

Kmu

Qlo

Qfy

Kmu

Qg QdQd

Qlo/Qp

Kmu

Qlo/QtmQsw

Qc

Qlo/Qtt

QcQc

Qto

Qc

Qfy

af

Twav

Qc

Tws

Qg

af Qlo/Qp

Qsw

Qfp

Qfp

QfpQfp

Qfp

QfpQfp

Qfp

Qfp

Qfp

Qfp

Qfp

QfpQfp

Qfp

Qfp

Qfp

Qfp

Qfp

Qlo/Qtt

Qac

af

Tws

Qlo/Qp

Qac

Qlo/Qp

af

Twm

Qfp

Qfp

Qc

afQc

Qc

Qsw

QswKmu Kmu

Qsw

Qc

Qsw

af

Qsw/Qlo

Qsw/Qlo

Qto

Twss

Twss

Twss

Qlo

Twss

Qsw

Qlo / Qtt

Qc

Qlo/Qtt

QbaQty

Qsw

Qsw

Qlo

Qsw

Qc

af

Qsw/Qlo

Qc

Qlo/Qty

Twm

Twav

Twm

Qls

Kwfl

Kicc

Qc

Kmu

Qlo

Kir

Kmvb

Twav

Qsw

af

CarterandCarter6147 TD

San Comp91 TD

Koch Explor8230 TD

A'

A

B'

B

RIFLE SYNCLINE

G R A N D

H O G B A C K

8

Qsw

Qsw

Qlo/Qtt

Qc

Qc

QcQc Qc

QcQac Qc

Qsw

Twav

af

Tws

Qsw

Qsw

Qlo

Qlo/Qp

Qty

Qlo

Qsw

Qlo

Qto

Qto

Tws

Qsw

Tws

Twav

Tws Tws

Kmu

Kmu QacKmu

Qc

Qc

Qc

Qc

Twm

Qsw

Kmu

Kmu

Qc

Qlo/Qp

Tws

Tws

Qsw

Tws

Qlo

Qsw

Qc

Qc

10

8

4

6

6

6

7

10

4

6

7

10

2

4

5

3

4

5

3

63

5

5

3

5

2

2

6

10

6

4

14

5

6

5

3

5

3

10

9

10

10

13

12

17

13

21

14

16

7

12

15

10

1318

17

18

21

24

14

28

28

2825

42

34

2843

4150

38

43

41

46

4744

46

45

50

43

44

50

5461

52

56

4845

48

52

63

59

41

64

54

55

68

7537

83

62

5588

75

68

59

52

43

59

55

44

56

44

57

47

6832

19

4037

44

47

61

12

75

56

7818

57

66

71

41

40

28

2929

64

29

79

77

16

46

68

87 74

57

66

62

54

76

59

64

47

4039

38

53

59

57

56

5841

43

37

51

37

37

64

40

45

46

54

31

22

40

26

54

53

49

55

47

43

54

44

43

76 69 75

28

88

79

83

79

58

68 23

70

61

66

83

18

52

50

52

48

53

46

10

Qc

54

5049

55

9

7

73

7