SAN ACACIO SAN LUIS TAYLOR RANCH EL VALLE CREEK STONEWALL 

GARCIA SANCHEZ

RESERVOIR 

LA VALLEY CULEBRA PEAK TORRES

COSTILLA 

AMALIA BIG COSTILLA

PEAK 

THE WALL VERMEJO PARK 

CERRO LATIR PEAK COMANCHE

POINT 

ASH 

MOUNTAIN 

VAN BREMMER

PARK 

DEVILS PARK GRABEN

COLORADO

NEW MEXICO 

COSTILLA

CREEK 

FAULT

Study 

 

Area

Figure 2. Tectonic map of the study area and vicinity showing the major bounding and internal structures. 

Figure covers part of the Sangre de Cristo Mountains, namely the southern half of the Culebra Range and the 

northernmost part of the Taos Range, along with the flanking basin-margins. SAN LUIS BASIN

BIG COSTILLA

 HORST

CULEBRA RANGE

CULEBRA

SAN

PEDRO HORST

RATON BASIN

GRABEN

36o45’

37o15’

105o30’ 105o15’ 105o00’

37o00’

Digital Elevation Model (DEM) shaded-relief image of the map area as illuminated from the northwest. Shaded-relief values derived from U.S. 

Geological Survey National Elevation Dataset (NED, http://ned.usgs.gov/) 10-meter elevation data, 2011.

10 KILOMETERS

0 10 MILES

0

5

5

LATIR VOLCANIC FIELD

TAOS RANGE

AND

SIM 2963 

(Machette and

others, 2008)

OFR 2003–15

(Kirkham and

others, 2003)

Colorado

Geological Survey

OFR 2007–1428 

(Fridrich and

Kirkham, 2007)

OFR 2007–1074

(Thompson and

others, 2007)

OFR 2004–8

(Kirkham and

others, 2004)

Colorado

Geological Survey

Study

 

Area

OFR 2009–1189 

(Fridrich and

others, 2009)

I–1907

(Lipman and Reed,

1989)

105o37’30” 105o30’00” 105o22’30” 105o15’00” 105o07’30” 105o00’00”

37o15’00”

37o07’30”

37o00’00”

SAN ACACIO 

COLORADO

NEW MEXICO 

36o45’00”

36o52’30”

Costillo Creek

Costilla

Creek

Comanche Creek

Costilla

Reservoir

SAN ACACIO SAN LUIS TAYLOR RANCH EL VALLE CREEK STONEWALL 

GARCIA LA VALLEY

CULEBRA PEAK TORRES

COSTILLA 

AMALIA BIG COSTILLA PEAK THE WALL VERMEJO PARK 

CERRO LATIR PEAK COMANCHE

POINT 

ASH MOUNTAIN VAN BREMMER PARK 

142 159 12

159

522

La Valley

Chama

San Luis

Torres

Costilla

Amalia

Stonewall

SANCHEZ RESERVOIR

Cerro

Figure 1. Index to sources of geologic data. Study area in yellow with adjacent U.S. Geological Survey 71⁄2-minute 

quadrangles. For U.S. Geological Survey publications, number, authorship, and year of publication are shown; for non-U.S. 

Geological Survey publications, the number, authorship, year of publication, and affiliation are shown.

Costilla

Creek

22

11

4

18

10

17

5 18

29 2

15

65

33 29

3

14

12

2 9

7

49

10

10

3

8

23

22

26

27

9

21

18

34

7

23

33

10

2

1

34

5

33 16

19

14

14

19

12

16

19

18

17

9

10

6

12

16

11

10

10

36

22

28

13

6

10

21

39

24

3

9

2

6 12

7

10 4 9

8

5

8

28

40

29

32

20

13

17

70

15

10

6

2

32

23 21

39

14

2

9

1

37

2

4

38

17

6 25

28

3

43

25

18

24

12

39

2

12

20

45

50

27

17

24

24

21

27

21

31

25

5

20

8

43

53

18

28

21

32

13

23

29

52

28

20

65

58

6

17

17 19 10

54

38

25

37

46

13

10

9

35

22

29

31

13

23

34

24

50

85

30

35

53

18

54

24

15

27

23

15

37

30

17

20

80

85

43

30 29

34

78

48

43

57

22

54

12

16

12

9

36 36

13

59

16

74

12

24 19

18

19

53

32

75

26

25

29

45

41

51

78

55

63

70

45

84

35

16

24

45

23

16

44

30

39

35

32

13

58

35

48

25

40

34

45

30

77 26 20

36 54

73

43

65 75 42

10 7 48

5

11

42

40

35

35

47

23

30

20

19

17

75 80

42

65

32

55

70

28

81

47

51

21 23

27

57

43

52

55

81

70

75

35

67

88

35

11

40

32

17

10

38

22

23

61

55 76

74

53

43

66

25

32

18

26

33 32

27

21

33

28

31

17

30

39

82

26

35

44

73

50

72

75 45

3

Qls

Tsb

Qls (Tsb)

Tsfc

Qa

Tb Qac

QTsf

Qay

Qa Qao

Qao

Tsb Qai Qay Qls

Xqs

Qac

Qc

Xqs

Xgg Qta

Qtp

Qa

Qtp

Tsb

Qa

Tsfc

Tb

Qfy

QTsf

YXp

Xfg

Tsb

Qc

Qac

Xfg

|Zg

|Zg

Qai?

Xqs

Xgg

Tsfc

Qc

Tsfc

Qac

Qgp

Qls

(Tsfc)

Qa

Xfg

Qtp

YXp

Qac

Qtp

Qac

Qc

Qta

Qta

YXp

Xfg

Qac

Tsfc

Qtp

Qtp

Qta

Xgg

Xfg

Qc

YXp

Qtp

Xfg

YXp Tri

Qao

Qta

Qc

Qtp

Qls Qrg

Qa

Qta

Tsfv

Qta

Qtb

Xqs

Qa

Tsfc

Qta Tb Qls

Tb

Qc

Qac

Qtp

Xq Qrg Qfy

Qfy

Qta

QTsf

Xq

Tbi

Tsb

Qtp

Tai

YXp

Qta

Qsw

YXp

Qtp

YXp YXp

Qac

Qta

Xfg

Qc

Tsfc

Qc

Qls

Qc

Xfg

Qls

Qa

Qtp

Tsb

Qta

Qac

Qta Xaa

Qac

YXp

Xfg

Qrg

Qta

Qsw

Xgg Qrg

Tsfc

Qa

Qc

Qa

Tsfc Qao

Xqs

Qtp

Xgg

Qta Qrg

Qac

Qac

Xgg

Qc

Qrg

Qa

QTsf

Qc

Qc

Qls

Qta

YXp

Xgg

Trt

Qc

QTsf

Qac

Tsfc

Shear

zone Ta

YXp

Qtp

Qac

Qa

Qc

Qa

Qai

Qa

Qac

Qsw

Qa

Xgg

Tsfc

Xfg

Xgg

|Zg

|Zg

Tsfv

Ta

w Tsb

Tsb

Xa

Qta

Qac

Qac

Xaa

Qc Xgg

Xa

Qa

Qc

Trt

Trt

Qay

Qfy

Qc

Tsfc

Ta

Xgg

Qls

Qac

Xaa

Ta Qls

(Trt)

Xgg

Qac

Qls

Qay

Qls Tsfc

(Trt)

Ta Xaa

Xaa

Qao

Xa

Qfy

Qc

Xho

Tsb

Tsfc

Qac Xgg

Qtp

Qta

Qac

Xgg

Xa

Qfy

Tb

Qta

Qac

Qc

Qc

YXp

PzZg

Tbi

Qta

Trt

Tsfc

Te

YXp

Tsfc

Xgg

Qfy

Qa

Tsfv

Qls

Ta

Xfg

YXp

Qtp Qtp

Xho

Qa

Qsw

Qtp

Qrg

Xfg

Te

Qa

Qc

Te

Xaa

YXp

Xaa Xgg

Xaa

Xgg Te

Qtb

Xaa

Xfg

Qtp

Qc

Tsfv Ta PzZg Qrg

Xfg

Tsfv

Xho Qtb?

YXp YXp

Xho

Qac

Trt

Tsfc Qc Qc

Qc

Te

Qfo

Xqct

YXp

Qta

Tsfc

YXp

YXp

Xaa YXp Tbx Qfy

Qc

Qrg

Qgp

Xaa

Xaa

Trt

Xaa

Tri

Tsfc

Tai

Xaa

Qgb

Xaa

Xfg

Xfg

Qc

Xgg

Xaa YXp Xho

Tsfc

Xaa

Xfg

Qfo

Qac

Tsfc

Qc Qta

Xaa

Tsfv Ta Tbi Xho

Qfy

Qac

YXp

YXp

Qfo

Qls

Xho

Xho

Tsfc

Qfy

Xaa

Qc

Tb Qls

Qc Qtb

Tsfc

YXp

Tri Xfg

YXp

Qtp

Tb

Xaa

Xa

Trt

Qfo

Tri

Qc

Qfy

Qgpb

Trt

Tsfc

Xqct

YXp Xaa

Qc

Tsfc Qc

Qa

Qc

Ypc

Qta

Qls

Qtb

Tsfc

Xfg

Qac

Tsfc

Qc Qac

Qls

Xfg

Tsfc

Qtp

Xfg

Qls

|Zg

|Zg

|Zg

|Zg

Qa Qls

YXp

YXp

Qgb

YXp

Tb

Qgp

Xa

Qls

Tsfc

Tri Qac

Tb

Qfy

Ypc

Ypc

Qac

Xfg

Xqct

Qfy

Qac

Ypc

Qls

Xfg

Xqct

Tsfc

Qc

Xaa

Xqct

YXp

Xa

Xfg

Tsfv

Tsfc

Xqs

Qtb?

Qbs

Xa

Ypc

Trt

Ta

Xqct Qc

Tri

Qfy

Qac

Tsfc

Ta Tb

Qgp

Tsfc

Trt

YXp

Tsfc

Ta

Qac

Qc

Xaa

Ypc

Qls

Tsfc

Qta

Qc

Qac

Tb

YXp

Qls

Qgb

Xho

Tsfc

Xaa

Qac

Tb

Tai

Qtp

Xaa

|Zg

|Zg

Qfy

Tsfc

Qc

Tb

Ta

YXp

Tsfc

Qao

Ta Qa

Ypc

Xqct

Qac

Qta

Xfg

Qls

Qls

Qta

Tsfv

Xa

Qao Xaa

Xqct

Tsfc

Qtp

Qrg

Qta

Xqct

Xqct

YXp

Tsfc

Qc YXp

PzZg

Qc

Qac

Qfy

Tsfc

Qfy

Qa

Qc Qc Qc

Xqct

Xqct

Trt

Qac

Xaa

Qc

Xfg

YXp

Qac

Ta

Xaa

Xaa

Tb

Tsfc

Qgb

Qgp

Tsfc

YXp

Tsfc

Xa

Tb

Qls

Qac

Qac

Qls

Ta

Xa

Ta

Qfy

Trt

Tsfv

Tsfc

YXp

Qc

YXp Qa YXp

af Tb

Qls

Ta

Qac

Xaa

Xqct

Qac

Ypc

PzZg

Qac

Xaa

Qac Tsfc

Te

Ta

Qac

Qac Tb

Tsfv

Xaa

Qc

YXp

Ta

YXp

Xq

YXp

Xqct

Tsfv

|Zg

|Zg

|Zg

|Zg

|Zg

|Zg

|Zg

|Zg

|Zg

|Zg

|Zg

|Zg

|Zg

|Zg Xa

Qac

Te

Tai

Ta

Xfg

Tb

Tsfc

Tai

Xfg

Ta

Qc

Qac

Xfg

Qls

Ta

Tai

Qac

Ta

Qls

Ta

Tsfv

Ta

Xaa

Xqct

Tsfc

Tb

Xaa

Tri YXp

Xqs YXp

Xq

Qac

Tb

Qc

Qls

YXp YXp

Xfg Te

Te

Xqs

YXp

Qc

Qac Qls

YXp Xaa

Xq

Qac

Tai

YXp Te

Ta

Tsfc

Qac

Qls

Tb

Tsfc

Tsfc

Qls

Xqct

Tri

Tai

Te

Xqs

Xaa

Te

Te

Tai

Ta

Tai

Tri

Ta

Qac

Qls

Tri

Tri

Qc

Qac

Ta

Tr

Ta

Tai

Ta

Tai

Trt

Tr

Tri

Trt

Tai

Qac

Tr

Tai

Te

Xq

Tri

Qac

Tsfv Tai

Xqs

Tai

Qc

Qac

Tsfv Tri

Qc

Tb

Tsfc

Tr Te

Ta

Tai

Tsfc

Ta

Tsfc

Qac

DESCRIPTION OF MAP UNITS

SURFICIAL DEPOSITS

Artificial fill deposits

Artificial fill (latest Holocene)—Engineered, compacted fill material composed of 

large angular rock fragments and finer material emplaced in a large earth-fill dam 

at the south end of Costilla Reservoir, near the southeast corner of the map area. 

Estimated thickness is 3–35 m

Alluvial deposits

Valley-floor alluvium (Holocene)—Mostly sand and gravel in stream channels; silty 

sand, sandy silt, and gravel lenses beneath flood plains less than about 2 m above 

modern streams. Estimated thickness 1–5 m

Sheetwash alluvium (Holocene and late? Pleistocene)—Mostly slightly pebbly, 

slightly silty to silty sand; forms alluvial aprons deposited by unconfined 

overland flow on gentle slopes. Estimated thickness 1–5 m

Stream alluvium (late and middle Pleistocene)—Fluvial deposits composed chiefly 

of interstratified pebbly sand and poorly sorted, clast-supported, cobbly pebble 

gravel that underlie alluvial surfaces along streams tributary to Costilla and 

Culebra Creeks in the western part of the map area. Clasts commonly are 

subangular to subrounded. Youngest unit (Qay) along Jarocito Creek locally 

includes outwash gravel (Qgp). Units locally may include debris-flow deposits. 

Estimated thickness 1–10 m 

Younger (lower) unit (late Pleistocene)—About 4 m above modern stream level

Intermediate unit (late and middle Pleistocene)—About 3 m above Jarocito 

Creek where deposits are partly buried by unit Qay; about 12 m above Ute Creek

Older (higher) unit (middle Pleistocene)—About 37–110 m above modern stream 

level

Outwash gravel (late and middle Pleistocene)—Glaciofluvial deposits composed 

chiefly of slightly bouldery, cobbly, pebble gravel deposited by melt-water 

streams flowing from former glaciers in the central part of map area. Boulders 

are 25–30 cm in diameter; clasts typically are moderately rounded to subangular. 

Estimated thickness 3–10 m

Outwash gravel of Pinedale age (late Pleistocene)—Underlies terrace remnants 

about 6 m above Casias Creek and about 12 m above Costilla Creek, near the 

eastern boundary of the map area. Probably coeval with nearby till deposited 

during the Pinedale glaciation (about 12–30 ka; Nelson and others, 1979; Benson 

and others, 2004, 2005). Deposits could be as old as 40–47 ka (Cole and others, 

2007), and may have been deposited during an early advance of Pinedale ice 

(Sturchio and others, 1994).

Outwash gravel of Bull Lake age (late and middle Pleistocene)— Underlies 

terrace remnants about 12 m above Casias Creek and about 24 m above Costilla 

Creek, near the eastern boundary of the map area. Probably coeval with nearby 

till deposited during the Bull Lake glaciation (about 120–170 ka; Sharp and 

others, 2003; Pierce, 2004). 

Outwash gravel of pre-Bull Lake age (middle Pleistocene)—Underlies a single 

small isolated terrace remnant about 32 m above Casias Creek and about 57 m 

above Costilla Creek near the eastern boundary of the map area. Probably 

deposited during a glacial episode that predated the Bull Lake glaciation.

Alluvial and mass-movement deposits

Alluvium and colluvium, undivided (Holocene and late Pleistocene)— Undifferentiated valley-floor alluvium (Qa), sheetwash alluvium (Qsw), and younger fan 

deposits (Qfy); includes small deposits of colluvium (Qc) along minor streams 

and on adjacent lower (toe) slopes. Estimated thickness 3–10 m

Fan deposits (Holocene to middle Pleistocene)—Mostly nonsorted to poorly sorted, 

slightly bouldery to bouldery, pebble and cobble gravel and locally pebbly and 

cobbly silty sand. Deposited chiefly by streams and debris flows in fan-shaped 

accumulations near base of moderate to steep slopes. Fan deposits locally include 

sheetwash deposits (Qsw), colluvium (Qc), and probably hyperconcentratedflow deposits. Estimated thickness 3–15 m 

Younger (lower) unit (Holocene and late Pleistocene)—Deposits commonly have 

well-preserved depositional morphology, and are at or near modern stream level

Older (higher) unit (middle Pleistocene)—Deposits commonly have muted 

depositional morphology, and are about 12–90 m above modern stream level. 

Unit is equivalent to older alluvial fan deposits of Lipman and Reed (1989). 

Mass-movement deposits

Talus deposits (Holocene and late Pleistocene)—Deposits composed of virtually 

unsorted, granule- to boulder-sized angular rock fragments in steep, roughly 

angle-of-repose aprons below steep slopes and cliffs. Probably formed chiefly by 

rock fall, rock slide, and, perhaps, locally by debris flow. Locally may include 

block-slope and block-stream deposits (Qbs). Estimated thickness 1–10 m 

Block-slope and block-stream deposits, undivided (Holocene and late Pleistocene)— 

Blocky deposits on steep slopes near the crest of the Sangre de Cristo Mountains, 

in southeastern part of the map area, are composed chiefly of angular blocks of 

pegmatite (Ypc) and quartz monzonite (Xqct). Block size probably decreases 

with increasing depth below the top of the deposits. Deposits of unit Qbs were 

probably formed chiefly by creep, freeze-thaw, and probably by periglacial 

processes during glacial episodes. Estimated thickness 1–10 m

Colluvium, undivided (Holocene to middle? Pleistocene)—Unsorted deposits 

formed by a variety of mass-wasting processes. Deposits consist of sand and 

finer material and angular clasts that range in size from granules to boulders. 

Unit includes material transported chiefly by creep, debris flow, sheetwash, 

hyperconcentrated flow, landslide, and by periglacial processes (such as 

solifluction) during glacial episodes. Thin deposits rich in eolian silt locally 

mantle frost-creep and solifluction deposits above tree line. The down-slope 

transport of these colluvial deposits may be locally due in part to the relatively 

high moisture-holding capacity of infiltrated eolian silt. Estimated thickness 3–15 m 

Landslide deposits (Holocene to middle? Pleistocene)—Deposits of unsorted and 

unstratified debris that commonly have hummocky topography. Many younger 

landslides are bounded upslope by crescent-shaped headwall scarps and 

downslope by lobate toes. The unit locally includes material displaced chiefly by 

rock slides, debris slides, debris flows, earth slides, and earth flows, as defined 

by Varnes and Cruden (1996). Near the west boundary of the map area, relatively 

intact slide blocks of Servilleta basalt, alluvial facies of the Santa Fe Group, and 

Amalia Tuff are displaced by sliding. These slide blocks are designated Qls

(Tsb), Qls (QTsf), and Qls (Trt), respectively. Landslide scarps in Tertiary and 

Proterozoic bedrock indicate the upslope limits of deep-seated bedrock creep or 

incipient sliding that did not produce landslide deposits. Estimated thickness 

5–45 m

Glacial deposits

Rock-glacier deposits (Holocene and latest Pleistocene)—Bouldery, lobate and 

probably locally tongue-shaped masses that commonly have steep fronts and 

flanks, and form in cirques, and along valley walls, above tree line in areas of 

high talus production. Deposits probably consist of a veneer of angular boulders 

that overlies a thick mass of rock rubble that contains finer interstitial rock 

fragments. The lower part of the unit is ice-cemented or has an ice core. Unit Qrg

locally may include minor talus deposits (Qta) displaced by post-depositional 

flowage, colluvium (Qc), and other mass-movement deposits. Estimated 

maximum thickness is 45 m

Till (late and middle Pleistocene)—Ice-deposited material composed chiefly of 

non-sorted and non-stratified, angular to subrounded boulders to granules in a 

sandy matrix. Probably locally includes stratified drift

Till of Pinedale age (late Pleistocene)—Deposits commonly form large prominent, sharp-crested lateral moraines that are very bouldery and have distinct 

constructional morphology. Unit locally may include till of Bull Lake age (Qtb). 

Radiocarbon (14C) and cosmogenic surface-exposure ages for correlative deposits 

in Colorado suggest that Qtp is about 12–30 ka (Nelson and others, 1979; 

Benson and others, 2004). Some deposits of Qtp may be older than 30 ka, 

because uranium-series ages of travertine in the northern Yellowstone area 

suggest an advance of Pinedale ice occurred about 34–47 ka (Sturchio and 

others, 1994). Estimated thickness is 1.5–100 m

Till of Bull Lake age (late and middle Pleistocene)—Deposits commonly form 

prominent lateral moraines that have rounded crests and that lie beyond the outer 

limit of till of Pinedale age (Qtp). Deposits near Jarocito, New Mex., are partly 

buried by stream alluvium of Qay. Unit Qtb locally may include till of Pinedale 

age (Qtp) and till of pre-Bull Lake age. K-Ar and 230Th/U analyses for correlative deposits in Wyoming suggest that Qtb is about 120–170 ka (Sharp and 

others, 2003; Pierce, 2004). Estimated thickness is 1.5–35 m

CENOZOIC BEDROCK

Sedimentary rocks

Santa Fe Group

Santa Fe Group (early Quaternary to Oligocene)—Syntectonic sedimentary and 

volcanic rocks deposited as fill in basins of the Rio Grande rift; everywhere 

divided into:

Alluvial facies, upper part (early Pleistocene to Pliocene)—Pebble to cobble 

sand-matrix conglomerate, pebbly sandstone and siltstone; poorly consolidated; 

ochre-colored; overlies 4.4–4.8 Ma Servilleta basalt (Tsb)

Alluvial facies, lower part (Pliocene to Miocene)—Pebble to boulder sand-matrix 

conglomerate, pebbly sandstone and siltstone; poorly to moderately consolidated; 

ochre-colored to light red; large clasts derived mainly from local Proterozoic 

bedrock and much lesser local volcanic and intrusive rocks—andesite (Ta), 

rhyolite lava (Tr), intrusive rhyolite porphyry (Tri), and Amalia tuff (Trt); 

underlies 4.4–4.8 Ma Servilleta basalt (Tsb); locally contains interbedded basalt 

or basaltic andesite flows yielding 40Ar/39Ar ages in the range of about 15 to 

about 11 Ma 

Volcaniclastic facies (early Miocene to late Oligocene)—Boulder to pebble 

sand-matrix conglomerate of mainly volcaniclastic composition; clasts of local 

andesite, rhyolite, and tuff (Ta, Tr, and Trt), along with lesser intermixed clasts of 

local Proterozoic bedrock; includes minor tuffaceous layers which appear to be 

reworked rather than juvenile

Rock-avalanche breccia (Miocene?)—Breccia composed of shattered Paleoproterozoic rocks, found as wedges locally interbedded within Santa Fe Group, alluvial 

facies, lower part (Tsfc). Mapped only in a single locale near Amalia, New Mex.; 

however, float of this breccia is common throughout the area of Tsfc to the north 

and east of this locale indicating it is more abundant than current mapping 

indicates

Conglomerates, mainly prevolcanic (lower Oligocene and Eocene)—Boulder 

conglomerates with clasts of various local Proterozoic lithologies, especially 

quartzite; but including fewer clasts of andesites (Ta) in uppermost part only; 

boulders and cobbles are well rounded; matrix commonly consists of deep 

maroon colored red clay where locally (rarely) exposed; generally equivalent to 

“Prevolcanic sedimentary rocks” of Lipman and Reed (1989) 

Volcanic rocks 

Servilleta basalt (Pliocene)—Tholeiitic basalt, thin dark-gray flows with small 

olivine phenocrysts; not dated in map area but dated in vicinity at 4.4 to 4.8 Ma 

(whole rock, 40Ar/39Ar, Thompson and others, 2007)

Mafic lava flows (Miocene)—Silicic alkali-olivine basalt and basaltic andesite lava 

flows, dark-gray, fine-grained, with sparse plagioclase and olivine phenocrysts; 

dated at about 11 to about 15 Ma to the north of map (40Ar/39Ar, whole-rock; 

Kirkham and others, 2005); equivalent to Hinsdale Formation of Thompson and 

others (2007)

Rhyolite lava (Oligocene)—Rhyolite lava with <0.5 percent phenocrysts of feldspar 

and quartz in a light grayish-blue groundmass; locally sperulitic or reddened by 

oxidation. Directly overlies the Amalia Tuff (Tat) in most exposures, and is 

presumed to be genetically related to it

Amalia Tuff (Oligocene)—Peralkaline rhyolite ash-flow tuff; mainly densely welded, 

with 10 to 20 percent phenocrysts of quartz and alkali feldspar (transitional 

sanidine-anorthoclase), and sparse to rare pyroxene, fayalite and sodic amphibole; dated at 25.5 Ma (40Ar/39Ar, feldspar; Lipman and Reed, 1989)

Andesites (Oligocene)—Thick sequence of lava flows, tuffs, lahars, and lesser 

interbedded volcaniclastic conglomerates and sandstones; mainly of andesitic 

composition but includes some dacites and rhyolites; generally equivalent to 

Conejos Formation of the San Juan Mountains; equivalent rocks to south of map 

have been called “precaldera volcanic rocks,” which Lipman and Reed (1989) 

divide into 15 map units ranging in age from about 30 to about 26 Ma 

Intrusive rocks

Mafic dike (Miocene)—Basaltic andesite dike with sparse plagioclase phenocrysts and 

quartz xenocrysts; presumed to be related to xenocrystic basaltic andesite (Tbx) 

of Lipman and Reed (1989), to south of map. If this proposed correlation is 

correct, Tbi is similar in age to the oldest of the (about 11 to 15 Ma) mafic lava 

flows (Tb) of northern part of map area, based on stratigraphic position

Felsic-composition intrusions (Oligocene?)—Hypabyssal stocks and smaller bodies 

of rhyolite porphyry; most of these intrusions are probably related to rhyolite 

(Tr), but some may be younger

Intermediate-composition intrusions (Oligocene?)—Hypabyssal sills and dikes of 

andesitic (diorite porphyry) composition; most of these intrusions are probably 

related to andesites (Ta), but some may be younger

LOWER PALEOZOIC OR NEOPROTEROZOIC DIKES

Gabbro (early Paleozoic or Neoproterozoic)—Dikes of nonfoliated quartz-bearing 

pyroxene gabbro, which cut foliated Paleoproterozoic and Mesoproterozoic rocks 

throughout the Sangre de Cristo Mountains, but do not cut overlying upper 

Paleozoic sedimentary rocks. A Rb-Sr isochron on a gabbro dike near the 

confluence of the Rio Costilla and Latir Creek (near the center of the southwest 

border of the map) gave an age of 670 Ma (data from Z.E. Peterman, U.S. 

Geological Survey, 1984, published by Lipman and Reed, 1989)

CRYSTALLINE BASEMENT ROCKS

[Note on coarse sawtooth-pattern contacts: Throughout the map area, many contacts within the 

Proterozoic crystalline basement rocks are depicted with a coarse sawtooth pattern to indicate very 

large-scale interfingering or gradation between adjacent map units. This type of contact is particularly appropriate for the pegmatite sheeted sill complex (Ypc), which interfingers so extensively 

with its host rocks that it cannot be shown as having definite boundaries at the scale of the map. In 

general, this pegmatite sheeted sill complex (Ypc) is mapped as solid where the sills constitute ≥ 90 

percent of the rock, and the sawteeth are used in those zones where sill concentration declines from 

about 90 percent of the rock to < 25 percent. Outlying pegmatite sills that are peripheral to the main 

mass of this intrusive complex are generalized, as are enclosed selvages of host-rock, and both are 

mapped mainly on ridge-tops above tree line, where exposures are best. Sawtooth boundaries are 

also used locally for contacts between the five compositional assemblages of mixed metavolcanic 

and metasedimentary Paloeproterozoic rocks, because the mixtures of different interbedded 

components in these rocks commonly change laterally in a very gradational way. 

The orientation of the sawteeth in all cases indicate the general trend of compositional bedding in 

the Proterozoic rocks. In contrast, the width of the sawteeth generally increases with the uncertainty 

in location of the highly gradational “contact,” and that uncertainty is largely a function of the 

extent of cover by humic and colluvial soils] 

Intrusive and metaintrusive

Pegmatite sheeted-sill complex (Mesoproterozoic)—granitic pegmatite found as a 

large complex of sills that have locally intruded so densely that remnant selvages 

of the host rock are rare; consists of quartz and two feldspars in eutectic 

proportions, along with minor to rare biotite and magnetite

Isolated pegmatites (Mesoproterozoic to Paleoproterozoic)—small pegmatite 

bodies that primarily are outliers of the pegmatite sheeted sill complex (Ypc); 

locally includes older (about 1.6–1.7 Ga) pegmatites related to local granitoid 

plutons (Xgg and Xqct)

Amphibolite (Paleoproterozoic)—Hornblende-plagioclase gneiss (meta-gabbro) 

locally found as small intrusions emplaced within granitoid plutons (Xgg and 

Xqct)

Quartz monzonite of Costilla Creek (Paleoproterozoic)—Gneissic biotite quartz 

monzonite, coarse-grained, moderately to strongly foliated; containing conspicuous augen of microcline 0.5 to 5 cm long; locally includes masses of pegmatite; 

an age of 1.644 Ga (U-Pb, zircon) was reported by Lipman and Reed (1989)

Gneissic granite of Jaroso Creek (Paleoproterozoic)—Monzogranite with a weak 

to strong superimposed gneissic foliation; locally includes masses of pegmatite; 

236Pb/238U SHRIMP dating of zircons from this granite yielded ages of 1.688 Ga 

and 1.689 Ga (analyst W.R. Premo, U.S. Geological Survey, reported in Kirkham 

and others, 2005) Metasedimentary

Quartzite (Paleoproterozoic)—Orthoquartzite, well-bedded with minor interbeds of 

muscovite schist; locally contains trace amounts of specular hematite

Muscovite- quartz schist (Paleoproterozoic)—Interbedded muscovite-quartz schist 

and lesser quartzite, locally contains feldspar, biotite, sillimanite, and garnet; 

interbeds of other rocks types, including felsic gneiss (meta-rhyolite) and 

amphibolite, are mostly minor except near sawtooth contacts

Mixed metasedimentary and metavolcanic

Felsic gneiss assemblage (Paleoproterozoic)—Mixed unit of compositionally 

layered metamorphic rocks dominated by gneisses composed of quartz and two 

feldspars, along with a trace to abundant biotite or muscovite. Mica-poor facies is 

probably meta-rhyolite based on preserved very-fine-grained equigranular 

texture and massive character, along with local remnant fabrics resembling 

flow-banding and phenocrysts. Mica-rich facies commonly have compositional 

bedding defined by variations in mica and quartz contents and appear metasedimentary. Interbeds of other rocks types, including amphibolites and mica schist 

are minor except near sawtooth contacts. Thin interbeds of banded iron formation 

(composed of quartz and specular hematite) are rare

Amphibolite assemblage (Paleoproterozoic)—Mixed unit composed dominantly 

(about 50 percent) of amphibolite (metabasalt) interbedded with a mixture of 

metavolcanic and metasedimentary rock types, including quartzites, mica-quartz 

schists, felsic gneiss, hornblende-orthoclase gneiss, and rare banded iron 

formation. Includes abundant pegmatite bodies too small to map separately. Not 

related to “Mixed unit of felsic gneiss and amphibolite” on the map to the 

northeast (Fridrich and Kirkham, 2007), which is entirely metavolcanic; instead 

correlative with “Bimodal and meta-sedimentary unit (Xb)” of that map, and to 

unit Xfa of the map to the east (fig. 1; Fridrich and others, 2009). “Mixed unit of 

felsic gneiss and amphibolite” of Lipman and Reed (1989) is mainly Xaa; 

however, greater discrimination is made on our map between areas dominated by 

felsic gneiss (Xfg) and ones dominated by amphibolites (Xaa) 

Hornblende-orthoclase gneiss assemblage (Paleoproterozoic)—Mixed unit 

composed dominantly of hornblende-orthoclase gneiss (interpreted as metatrachyte), with minor to moderately abundant interbeds of amphibolite, felsic 

gneiss, and mica schist

af

Qa

Qsw

Qay

Qai

Qao

Qgp

Qgb

Qgbp

Qac

Qfy

Qfo

Qta

Qbs

Qc

Qls

Qrg

Qtp

Qtb

QTsf

Tsfc

Tbx

Tsfv

Te

Tsb

Tb

Tr

Trt

Ta

Tbi

Tri

Tai

|Zg

Ypc

YXp

Xa

Xqct

Xgg

Xq

Xqs

Xfg

Xaa

Xho

REFERENCES CITED

Benson, Larry, Madole, Richard, Landis, Gary, and Gosse, John, 2005, New data for late Pleistocene alpine glaciation from southwestern Colorado: Quaternary Science Reviews, v. 24, p. 

46–65.

Benson, Larry, Madole, Richard, Phillips, William, Landis, Gary, Thomas, Terry, and Kubic, Peter, 

2004, The probable importance of snow and sediment shielding on cosmogenic ages of 

north-central Colorado Pinedale and pre-Pinedale moraines: Quaternary Science Reviews, v. 

23, p. 193−206.

Cole, J.C., Mahan, S.A., Stone, B.D., and Shroba, R.R., 2007, Ages of Quaternary Rio Grande 

terrace-fill deposits, Albuquerque area, New Mexico: New Mexico Bureau of Geology and 

Mineral Resources, New Mexico Geology, v. 29, no. 4, p 122−132.

Fridrich, C.J., and Kirkham, R.M., 2007, Geologic map of the Culebra Peak area, Las Animas and 

Costilla Counties, Colorado: U. S. Geological Survey Open-File Report 2007−1428, scale 

1:50,000.

Fridrich, C.J., Shroba, R.R, Pillmore, C.L., and Hudson, A.M., 2009, Preliminary Geologic Map of 

the Vermejo Peak area, Colfax and Taos Counties, New Mexico and Las Animas and Costilla 

Counties, Colorado: U. S. Geological Survey Open-File Report 2009–1189, scale 1:50,000.

Fridrich, C.J., and Workman, J.B., 2009, Peripheral structures of the Rio Grande Rift in the Sangre 

de Cristo Mountains, around the Colorado-New Mexico border [abs.]: American Geophysical 

Union Fall Meeting, abstract T53D–1612.

Kirkham, R.M., Keller, J.W., Lindsay, N.R., and Price, J.B., 2005, Geologic map of the southern 

half of the Culebra Peak quadrangle, Costilla and Las Animas Counties, Colorado: Colorado 

Geological Survey Open-File Report 2005−3, scale 1:24,000. 

Kirkham, R.M., Lufkin, J.L., Lindsay, N.R., and Dickens, K.E., 2004, Geologic map of the La 

Valley quadrangle, Costilla County, Colorado: Colorado Geological Survey Open-File Report 

2004–8, scale 1:24,000.

Kirkham, R.M., Shaver, K.C., Lindsay, N.R., and Wallace, A.R., 2003, Geologic map of the Taylor 

ranch quadrangle, Costilla County, Colorado: Colorado Geological Survey Open-File Report 

2003–15, scale 1:24,000.

Larson, E. E., Patterson, P. E., Curtis, G. Drake, R., and Mutschler, F. E., 1985, Petrologic, 

paleomagnetic, and structural evidence for a Paleozoic rift system in Oklahoma, New Mexico, 

Colorado, and Utah: Geological Society of America Bulletin, v. 96, 1364–1372.

Lipman, P.W., and Reed, J.C., Jr., 1989, Geologic map of the Latir volcanic field and adjacent 

areas, northern New Mexico: U. S. Geological Survey Map I–1907, 2 sheets, scale 1:48,000.

Machette, M.N, Thompson, R.A., and Drenth, B.J., 2008, Geologic Map of the San Luis 

quadrangle, Costilla County, Colorado: U.S. Geological Survey Scientific Investigations Map 

2963, scale 1:24,000. 

Nelson, A.R., Millington, A.C., Andrews, J.T., and Nichols, Harvey, 1979, Radiocarbon-dated upper 

Pleistocene glacial sequence, Fraser Valley, Colorado Front Range: Geology, v. 7, p. 410−414.

Pierce, K.L., 2004, Pleistocene glaciation of the Rocky Mountains, in Gillespie, A.R., Porter, S.C., 

and Atwater, B.F., eds., The Quaternary Period in the United States: Amsterdam, Elsevier, p. 63−76.

Sharp, W.D., Ludwig, K.R., Chadwick, O.A., Amundson, Ronald, and Glaser, L.L., 2003, Dating 

fluvial terraces by 230Th/U on pedogenic carbonate, Wind River basin, Wyoming: Quaternary 

Research, v. 59, p. 139−150.

Sturchio, N.C., Pierce, K.L., Murrell, M.T., and Sorey, M.L., 1994, Uranium-series ages of 

travertines and timing of the last glaciation in the northern Yellowstone area, WyomingMontana: Quaternary Research, v. 41, p. 265−277.

Thompson, R.A., Machette, M.N., and Drenth, B.J., 2007, Preliminary Geologic map of the 

Sanchez Reservoir quadrangle and the eastern part of the Garcia quadrangle, Costilla County, 

Colorado: U.S. Geological Survey Open File Report 2007–1074, scale 1:24,000.

Varnes, D.J., and Cruden, D.M., 1996, Slope movement types and process, in Turner, A.K., and

Schuster, R.L., eds., Landslides—Investigation and mitigation, Special Report 247: Washington, D.C., Academy Press, National Research Council, Transportation Research Board Special 

Report 247, 673 p.

GEOLOGIC SUMMARY

The map area extends over all but the northernmost part of the Big Costilla horst (fig. 2), a late 

Cenozoic uplift of Proterozoic rocks that is largely surrounded by down-faulted Cenozoic rocks 

exposed at significantly lower elevations. This horst is bounded on the northwest side by the San 

Pedro horst and Culebra graben, on the northeast and east sides by the Devils Park graben (Fridrich 

and Workman, 2009), and on the southwest side by the Latir volcanic field (fig. 2). The area of this 

volcanic field has undergone significantly greater extension than the area to the north of Costilla 

Creek (Fridrich and Workman, 2009). The horsts and grabens discussed above are all peripheral 

structures on the eastern flank of the San Luis basin, which is the axial part of the about 26 

Ma-to-present Rio Grande rift at the latitude of the map (fig. 2; Fridrich and Workman, 2009). The 

Laramide-age (about 70 to about 40 Ma) Raton basin lies to the east of the Culebra segment of the 

Sangre de Cristo Mountains (fig. 2).

Cenozoic strata in the map area include: (1) Eocene to lower Oligocene boulder conglomerates 

(Te) that predate the Rio Grande rift; (2) about 30 to about 26 Ma volcanic rocks of the Latir 

volcanic field (Ta, Trt, and Tr); which were erupted shortly before or at the advent of rifting; and 

(3) the Santa Fe Group, which represents syn-rift basin-fill sedimentary strata, and is divided into 

three map units (Tsfv, Tsfc, and QTsf). The oldest subunit of the Santa Fe Group (Tsfv) is 

overwhelmingly volcaniclastic and has strongly fanning (diminishing-upward) stratal dips. The 

overlying remainder of the Santa Fe Group consists predominantly of alluvial conglomerates, with 

clasts mainly of Proterozoic rocks, and is divided into two parts, subunits Tsfc and QTsf, that 

predate and postdate the 4.4–4.8 Ma Servilleta basalt (Tsb), respectively. An older group of 

interbedded volcanic rocks locally found within the middle map unit of the Santa Fe Group (Tsfc) 

consists of flows of basalt or basaltic andesite (Tb) and lesser dacite (northeast of the map), ranging 

in age from about 11 to about 15 Ma (Thompson and others, 2007). 

Subvolcanic Cenozoic intrusions in the map area include basaltic (Tbi), rhyolitic (Tri), and 

andesitic (Tai) stocks and dikes, which are interpreted as being related to Cenozoic extrusive rocks 

of the same three compositions (Tb, Tr, and Ta), and probably are approximately the same in age; 

however, younger ages for some of the intrusions are possible. The vast majority of the intrusions 

in the map area were emplaced along or in the immediate vicinity of the Costilla Creek fault, a 

large fault with predominantly strike-slip offset that intervenes between the Big Costilla horst and 

the structural block immediately to the southwest that hosts the Latir volcanic field (fig. 2).

The western range-front fault system of the Sangre de Cristo Mountains shows evidence of 

recent activity as close as 1 kilometer north of the map area (Kirkham and others, 2003, 2004; 

Thompson and others, 2007); however, there is no evidence of recent offset on range-front faults in 

the map area itself. An array of small (about 2 to about 10 m) offset northeast-striking normal faults 

in the northwestern part of the map cut Santa Fe Group strata (QTsf) that overlie the Servilleta 

basalt. Whereas the youngest of the QTsf strata may locally be as young as early Pleistocene, these 

northeast-striking faults lack discernable primary geomorphic expression and thus probably are no 

younger than middle Pleistocene. Whereas the post-about 4.5 Ma offsets on these faults are very 

small, exposures on the steep north slope of Costilla Creek valley show that at least one of these is 

a sizeable fault at deeper levels where it cuts Miocene and older rocks. This array of small-offset 

northeast-striking normal faults in the northwestern part of the map may reflect minor 

non-seismogenic reactivation of Miocene faults.

The Proterozoic rocks of the Culebra Range part of the Sangre de Cristo Mountains can be 

grouped into five major packages, from oldest to youngest: (1) a sequence of strictly metavolcanic 

(mainly meta-andesite) rocks, which are not exposed in the map area, (2) an overlying sequence of 

interbedded metasedimentary and bimodal metavolcanic rocks, (3) plutonic meta-intrusive rocks of 

mainly granitoid composition, (4) a sheeted-sill complex of pegmatite, and (5) non-foliated gabbro 

dikes. 

The first and oldest package of rocks is exposed to the northeast of the map, in the Culebra 

Peak area, and is strictly metavolcanic consisting mainly of meta-andesite and meta-dacite (Fridrich 

and Kirkham, 2007). 

The second package of rocks is the oldest exposed group of rocks in the map area, and it is 

divided into five map units based on composition (see Correlation of Map Units and Description of 

Map Units). These five map units include two fairly pure lithologies: quartzite (Xq) and quartzmuscovite schist (Xqs), as well as three mixed assemblages, each dominated by a particular 

lithology: amphibolite (meta-basalt; Xaa), felsic gneiss (mixed meta-rhyolite and metasedimentary quartz-feldspar-mica gneiss; Xfg), and hornblende-orthoclase gneiss (meta-trachyte; 

Xho). 

The third package of rocks, which consists mainly of two granitoid plutons, intrudes the mixed 

metasedimentary and metavolcanic rocks of the map area (Xq, Xqs, Xaa, Xfg, and Xho). The 

gneissic granite of Jaroso Creek (Xgg) is exposed in the northern part of the map and has been 

dated in the adjacent La Valley, Colo., 71⁄2-minute quadrangle at 1,688 Ma (U-Pb, zircon; 

previously published in Kirkham and others, 2004, 2005). The quartz monzonite of Costilla Creek 

(Xqct) is exposed in the southern part of the map and has been dated at 1,644 Ma (U-Pb, zircon; 

Lipman and Reed, 1989). This third package (meta-intrusive rocks) also includes a minor unit 

consisting of amphibolites (Xa; meta-basaltic) rocks that are emplaced within the plutonic granitoid 

intrusions.

The fourth package of Proterozoic rocks consists of a large sheeted sill complex of pegmatite 

(Ypc) that is exposed throughout the south-central part of the map area. This complex intrudes the 

quartz monzonite of Costilla Creek (Xqct) and its host rocks. The sheeted sill complex is nonfoliated, whereas the rocks it intrudes typically are strongly foliated and lineated, including some older 

pegmatite that is locally part of the about 1.7-Ga host rocks. U-Pb dating of the sheeted sill 

complex (Ypc) has yielded only a very rough estimate of its age, about 1,400 Ma, owing to the 

strongly metamict nature of the zircons found in it (W.R. Premo, written commun., U.S. Geological 

Survey, 2011). Isolated pegmatites (YXp) of the map area consist mainly of outliers related to the 

sheeted sill complex, but may also include some older pegmatites that may be related to the about 

1,640–1,690-Ma granitoid plutons. 

The fifth and youngest package of Proterozoic (or early Paleozoic) rocks consists of 

non-foliated gabbro dikes (|Zg) that are predominantly subvertical and northwest-striking. 

Whereas stratigraphic constraints in the Sangre de Cristo Mountains only bracket these dikes 

between about 1,400 Ma and the Pennsylvanian period (about 320 Ma), a Neoproterozoic age is 

most likely based on a Rb-Sr isochron of a gabbro dike near the confluence of Costilla Creek and 

Latir Creek (near the center of the southwest border of the map; Lipman and Reed, 1989). 

However, these dikes may possibly be as young as early Paleozoic (Larson and others, 1985).

Metamorphic fabrics in the Paleoproterozoic rocks are complex. Map data gathered in this 

study indicate that there are at least four different foliations in the rocks and at least three lineations 

reflecting a complex, multi-stage tectonic history. Because of these complex structural fabrics, the 

best developed foliation and the best developed lineation in single locales are not necessarily 

coplanar. 

INTRODUCTION

This map covers the Big Costilla Peak, New Mex.–Colo. quadrangle and adjacent parts of 

three other 71⁄2-minute quadrangles: Amalia, New Mex.–Colo.; Latir Peaks, New Mex.; and 

Comanche Point, New Mex. (fig. 1). The study area is in the southwesternmost part of that portion 

of the Sangre de Cristo Mountains known as the Culebra Range. The Taos Range part lies to the 

southwest of Costilla Creek and its tributary, Comanche Creek. This study fills a gap in detailed 

bedrock geologic mapping in the Sangre de Cristo Mountains between previous maps, listed 

clockwise from northwest by the authors (see fig. 1): Machette and others, 2008; Kirkham and 

others, 2003; Kirkham and others, 2004; Fridrich and Kirkham, 2007; Fridrich and others, 2009; 

Lipman and Reed, 1989; Kirkham and others, 2004; and Thompson and others, 2007. Nearly all of 

the mapping presented is new original detailed work; however, a thin strip of geologic mapping 

along Costilla Creek was modified from Lipman and Reed (1989) in order to show the evidence for 

two major late Tertiary faults that are largely concealed under alluvium of the river valley. 

Field work for this map was carried out by the authors during the summers of 2007 through 

2009. The map was compiled using a photogrammetric plotter and recent aerial photography 

(1:40,000-scale black-and-white National Aerial Photography Program (NAPP) photographs taken 

in 1999, available at http://egsc.usgs.gov/isb/pubs/booklets/aerial/aerial.html), in conjunction with 

Global Positioning System (GPS) measurements taken in the field. 

CORRELATION OF MAP UNITS

SURFICIAL DEPOSITS

Artificial

fill

Alluvial

deposits

Alluvial and

mass-movement

deposits

Mass-movement 

deposits

Glacial

deposits

CENOZOIC BEDROCK

Sedimentary rocks Volcanic rocks Intrusive rocks

Holocene

Pleistocene

Pliocene

Miocene

Oligocene

Eocene

QUATERNARY

LOWER PALEOZOIC

OR NEOPROTEROZOIC

MESOPROTEROZOIC

PALEOPROTEROZOIC

CRYSTALLINE BASEMENT ROCKS

Metasedimentary

Mixed metasedimentary and metavolcanicIntrusive and

metaintrusive

Unconformity

af Qa

Qsw Qay

Qai

Qao

Qgp

Qgb

Qgpb

Qac Qfy

Qfo

Qta Qbs

Qc Qls

Qrg

Qtp

Qtb

QTsf

Tsfc

Tsfv

Tsb

Tb

Tr

Trt

Ta

Te

Tbi

Tri

Tai

|Zg

Xqct

Xgg

Xa

Ypc

Xq Xqs Xfg Xaa Xho

Yxp

? ?

?

?

?

?

Tbx

?

TERTIARY

Santa Fe

Group

LOWER PALEOZOIC

OR NEOPROTEROZOIC DIKES

EXPLANATION

Contact—Dashed where approximately located; short dash where uncertain and (or) 

queried

Gradational contact—Large-scale interfingering or gradation between adjacent 

Proterozoic crystalline basement rocks represented using a coarse sawtooth 

pattern. The orientation of the sawteeth indicates the general trend of compositional bedding in the Proterozoic rocks. The width of the sawteeth generally 

increases with the uncertainty in location of the highly gradational contact

Crest line of moraine

Landslide scarp—Hachures at base of scarp

Erosional scarp—Hachures at base of scarp

Fault—Dashed where approximately located; dotted where concealed

Normal fault—Dashed where approximately located; dotted where concealed. Bar 

and ball on apparent downthrown side

Strike-Slip fault—Right lateral offset. Dashed where approximately located; dotted 

where concealed.

Vertical bedding—Showing strike 

Inclined bedding—Showing strike and dip

Overturned bedding—Showing strike and dip

Inclined oliation in metamorphic rock—Showing strike and dip; with foliation 

arrow showing bearing and plunge

Inclined foliation in igneous rock—Showing strike and dip

Lineation—Showing bearing and plunge

Minor syncline—Showing bearing and plunge

Fault attitude—Showing strike and dip

Rake on fault—Showing bearing and rake

Shear zone

5

27

12

17

80

53

88

35

8

U.S. Department of the Interior

U.S. Geological Survey

Open-File Report 2012–1041

105°30' 27'30" 25' R.13 E. R.14 E. R.14 E. R.15 E. 456 457 458 460 461 462 463 464 465 R.15 E. R.16 E. 467 468 469 471 472 473 475 477000m E. 476 470 466000m E. 73000 FEET

105°22'30" 17'30" 105°15' 76000 FEET 20' 36°47'30"

36°47'30"

Base from U.S. Geological Survey Big Costilla Peak, New Mex.–Colo.,1963; Amalia, New 

Mex.–Colo., 1963; Latir Peak, New Mex., 1963; and Comanche Point, New Mex. 1963, 1:24,000.

Polyconic projection. North American Datum of 1927 (NAD 27)

10,000-foot grids based on New Mexico coordinate system, central zone, and Colorado 

coordinate system, south zone

1000-meter Universal Transverse Mercator grid ticks, zone 13

GIS files projected in Universal Transverse Mercator

SCALE 1: 24 000

1 1/ 2 0 1 MILE

1000 0 1000 2000 3000 4000 5000 6000 7000 FEET

1 .5 0 1 KILOMETER

Field work was carried out by C.J. Fridrich, R.R. Shroba, and A.M. Hudson in the 

summers of 2007–2009. A thin strip of geologic mapping along Costilla Creek was 

modified from Lipman and Reed (1989)

GIS database and digital cartographic base by T.R. Brandt

Edit and digital layout by L.J. Binder

COLORADO

MAP LOCATION

NEW MEXICO APPROXIMATE MEAN

DECLINATION, 2009 TRUE NORTH

MAGNETIC NORTH

9°

CONTOUR INTERVAL 40 FEET

Preliminary Geologic Map of the Big Costilla Peak Area, Taos County, New Mexico, and Costilla County, Colorado

By

Christopher J. Fridrich,1

 Ralph R. Shroba,1 and Adam M. Hudson2

2012

Suggested citation:

Fridrich, C.J., Shroba, R.R., and Hudson, A.M., 2012, Preliminary 

geologic map of the Big Costilla Peak area, Taos County, New Mexico, 

and Costilla County, Colorado: U.S. Geological Survey Open-File Report 

2012–1041, scale 1:24,000. 

Publishing support provided by: 

Denver Publishing Service Center

Manuscript approved for publication on Feb. 28, 2012

Any use of trade, product or firm 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 for other than personal use must be secured 

from the copyright owner.

Although these data have been processed successfully on a computer system 

at the U.S. Geological Survey, no warranty expressed or implied is made 

regarding the display or utility of the data on any other system, or for general 

or scientific purposes, nor shall the act of distribution constitute any such 

warranty. The U.S. Geological Survey shall not be held liable for improper or 

incorrect use of the data described and/or contained herein.

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http://esp.cr.usgs.gov/ 

CONVERSION FACTORS

Multiply By To obtain

meter (m)

millimeters (mm)

0.3048

2.54

1.609 kilometer (km)

square kilometer (km2 2.590 )

inch (in.)

foot (ft)

mile (mi)

square mile (mi2)

COSTILLA

CREEK

FAULT

COSTILLA

CREEK

FAULT

1U.S. Geological Survey

2Montana State University, Bozeman, Mont.

f