science 

uses

for a changing world

Geochemical Baselines and Maps Showing 

Acid-Neutralizing Capacity and Potential 

Release of Total Dissolved Solids of Stream 

and Spring Waters from Different Rock 

Compositional Types from Mountainous 

Watersheds in the Gunnison, Uncompahgre, 

and Grand Mesa National Forest, Colorado

by William R. Miller1 

Open-File Report 99-580

1999

This report is preliminary and has not been reviewed for conformity with the U.S. Geological 

Survey editorial standards and stratigraphic nomenclature. Any use of trade product or firm 

names is for descriptive purposes only and does not imply endorsement by the U.S. Government.

U.S. DEPARTMENT OF THE INTERIOR 

U.S. GEOLOGICAL SURVEY

'Denver, Colorado
Introduction

When precipitation, as rain and snow, falls within a mountainous watershed, water comes 

into contact with rock minerals and chemical weathering is initiated. Chemical weathering 

involves the congruent dissolution of minerals such as calcite or the incongruent dissolution and 

transformation of minerals such as plagioclase to clay minerals. These chemical weathering 

processes release elements to the natural waters of a watershed. Therefore the chemical 

composition of natural waters that evolve within a watershed, in the absence anthropogenic 

input, is determined mostly by the chemical composition of rocks within the basin. In addition, 

generally minor input can come from atmospheric precipitation or dry fall. Biota activity in the 

soil zone concentrates CO2 , and biota may concentrate or consume species. Other factors such 

as rates of mechanical erosion, the grain size and crystallinity of the rock minerals, amount and 

distribution of precipitation, temperature, and type and amount of vegetation influence mainly 

the rates of the water-rock reactions, but the chemical composition of the rocks is the 

fundamental factor which determines the type of waters which evolve within a headwater 

watershed. The major element composition of most rock types are generally known from 

geologic maps, giving insight into the expected major element composition of natural waters of 

the basin in question. The is not true with respect to trace elements which can vary two or more 

orders of magnitude within similar rock types.

This background geochemistry of the natural waters of a basin can be modified by input 

from anthropogenic processes such as nuclear fallout, atmospheric emission, or mining wastes. 

There is probably no place in the world in which the natural background composition of waters 

of an area has not been modified to some extent by anthropogenic processes; the effects of these 

processes are always superimposed on the natural background geochemistry. But areas, 

particularly mountainous headwater areas, can be selected which are only minimally affected by 

anthropogenic input. Headwaters areas are the highest and the most remote regions of a 

watershed. It is where waters are imprinted by the chemical composition of the rocks which 

underlie the watershed. Many of these headwater areas are critical to water resource 

development. These areas have comparatively high precipitation and low evapotranspiration 

rates and generally lack extensive groundwater reservoirs, due to shallow soils and extensive 

outcroppings of bedrock. The distribution of water available in streams in these mountainous 

headwater areas are uneven throughout the year with high flows during the spring runoff and 

after summer thunderstorms. In the winter, water available in streams and springs reaches a 

minimum when element concentrations are high but mass flux is low. At this time, runoff is fed 

mainly by the recession of the groundwater reservoir. Mountainous headwaters react quickly to 

changes in input and are especially vulnerable to anthropogenic impact.

1
Geochemical baselines, at a particular point in time for stream and spring waters, can be 

determined in these mountainous headwaters, and may approximate the natural background 

geochemistry. This information is useful for an understanding of the processes responsible for 

the chemical composition of waters of a watershed. In addition, because water geochemistry is 

sensitive to changes in the environment, by monitoring water geochemistry in these mountainous 

headwater areas and comparing the results to the earlier baseline data, changes in the 

environment within the basin can be determined. This geochemical baseline is an approximation 

of the natural background and if remediation is needed in the future because of anthropogenic 

contamination, this baseline is the ideal goal. Note that it is not feasible to require geochemical 

quality standards lower than this natural baseline.

The purpose of this study is to determine for different rock compositional types, the range 

of species and other geochemical parameters and characterize the baseline geochemistry of 

stream and spring waters evolving within mountainous watersheds within three National Forests 

in western Colorado. The ranges of species and other parameters are determined for each of the 

major rock compositional types in the Gunnison, Uncompahgre, and Grand Mesa National 

Forests (GMUG) and spacial maps of mean pH values, potential release of total dissolved solids, 

and acid-neutralizing capacity were determined for each of the National Forests. In addition, 

processes responsible for the control and mobility of the elements in the natural waters were 

investigated. These geochemical baselines demonstrate the importance of rock composition in 

determining the types of waters evolving in these headwater areas, and will also allow the 

recognition of any significant changes in water quality that may occur in the future in these 

mountainous headwater areas.

Study Area

The study area is located in Western Colorado and includes the Gunnison, Uncompahgre, 

and Grand Mesa National Forests (fig. 1). The eastern part of the study area occurs within the 

Southern Rocky Mountains and the western part occurs in the Colorado Plateau physiographic 

province (Hunt, 1974). The mountain ranges and intermountain basins generally trend northnorthwest. Dendritic drainage patterns are well developed and most of the area is of moderate to 

high relief. Uncompahgre Peak at 14,390 feet is the highest point in the study area. The lowest 

point is along the western flank of Battlement Mesa at around 6000 feet. The main river systems 

that drain the area are the Uncompahgre-Gunnison Rivers and the San Miguel-Dolores Rivers. 

Both river systems drain into the Colorado River after leaving the study area. Annual 

precipitation ranges from around 20 inches in the northwestern part of the study area to more 

than 50 inches (Colorado Climate Center, 1984). The higher elevations receive the highest
Grand 

Junction

Grand Mesa NF

/ Denver

' r~^_ ^ Gunnison NF

^ ~"-r 

Delta \ \

! J

-s Colorado

Uncompahgre NF

Figure 1. Map showing locations of the three National Forests.
precipitation, mainly as snow during the winter. Winter weather is influenced by storm systems 

originating from the Pacific Ocean. Snow pack above 10,000 feet begins to accumulate in late 

October and reaches a maximum in mid-April (Benedic, 1991). In summer, particularly July, 

August, and early September, moist air from the Gulf of Mexico leads to afternoon 

thunderstorms and storm runoff. Snowmelt runoff usually runs from April through July and 

peaks in May through June (Apodaca and others, 1996).

Because of the large differences in altitude, the climate in the study area varies from coolhumid in the higher mountains to semi-arid in the lower elevations. Mean annual temperature 

varies from around 32 degrees in the highest elevations to above 50 degrees in the lower 

elevations (Benci and McKee, 1977). The natural vegetation in the study area is strongly zoned 

by altitude and is divided into six general groups based on the classification of the U.S. Dept. of 

Agriculture (1972). Except for grasslands which can occur in both higher and lower elevations, 

the groups from the highest to the lowest elevation are: 1) alpine tundra, 2) subalpine forest, 3) 

piny on pine-juniper forest, 4) oak scrubland, 5) sagebrush scrubland, and 6) grassland. 

Timberline is around 11,000 feet, but varies as a function of slope orientation to sun, rock/soil 

cover, and other effects.

Geology

Bedrock geology in the three National Forests ranges from Proterozoic metamorphic and 

crystalline rocks to Quaternary sediments (Table 1). Major rock types within the Grand Mesa 

National Forest (fig. 2) include Pliocene to Miocene basalt flows and associated tuff, breccia, and 

conglomerate of late volcanic bimodal suite, which occurs along the top of Grand Mesa, Eocene 

Green River Formation of marlstone, sandstone, and oil shale, Uinta Formation of sandstone and 

siltstone, and Eocene to Paleocene Wasatch and Ohio Creek Formations of claystone, mudstone, 

sandstone, and conglomerate. These Tertiary sedimentary rocks occur mainly along the flanks of 

Grand Mesa and the top and flanks of Battlement Mesa.

The major rock types of the Uncompahgre National Forest (fig. 3) consist of Pliocene to 

Miocene basalt flows and associated tuff, breccia, and conglomerate, Oligocene ash-flow tuff, 

Oligocene inter-ash flow quartz latitic lava and breccia, Oligocene andesitic lava and breccia, 

Cretaceous Mancos Shale, Cretaceous and Jurassic Dakota, Purgatoire, and Morrison Formations 

of sandstone, shale, claystone, and conglomerate, Jurassic Morrison and Summerville 

Formations, and Entrada Sandstone of claystone, sandstone, mudstone, shale, siltstone, and 

limestone, Triassic and Permian Windgate Sandstone, Chinle Formation, and Dolores Formation 

of siltstone, sandstone and conglomerate, Permian Cutler Formation of arkosic sandstone, 

siltstone, and conglomerate, Pennsylvanian Hermosa Formation of arkosic sandstone,
Table 1. Generalized stratigraphic column of dominant rocks in the Grand Mesa, Uncompahgre, and Gunnison N

Period Epoch Rock Unit or Type Domiant Lithology

Quaternary

Tertiary 

Tertiary 

Tertiary 

Tertiary 

Tertiary 

Tertiary 

Tertiary 

Tertiary

Cretaceous

Cretaceous

Cretaceous

Jurassic

Jurassic

Triassic and Permian

Permian and Pennsyvanian

Mississipian through Cambrian

Precambrian

Holocene and Pleistoc

Pliocene and Miocene

Oligocene

Oligocene

Oligocene

Eocene and Oligocene

Eocene

Eocene

Eocene

Late

Late

Early

Late

Middle

alluvium, colluvium, glacial, and

landslide deposits

basalt flows and associated rocks

ash-flow tuff

quartz latitic lava and breccia

andesitic lava and associated rocks

intrusive stocks and dikes

Uinta Formation

Green River Formation

Wasatch Formation and

Ohio Creek Formation

Mesavede Group

Mancos Shale

Dakoka Ss, Burro Canyon Fm

Morrison Fm, Summerville Fm

Entrada Sandstone

Wingate Ss, Chinle Fm, Dolores Fm

Cutler Fm, Maroon Fm, Minturn Fm,

Belden Fm, Hermosa Fm

Leadville Ls, Ouray Ls, Elbert Fm,

Chaffee Group, Fremont Ls, Harding Ss,

Manitiou Dol, Sawatch Quartzite

metamorphic and igneous rocks__

silt, sand, clay, gravel, bou

lava flows, tuff, breccia, an

rhyolitic ash-flow tuff

latitic lava and breccia

andesitic lava, breccia, tuff

felsic and intermediate com

sandstone and siltstone

marlstone, sandstone, silts

claystone, modstone, sand

mudstone, shale, coal, and 

shale and calcareous shale 

sandstone, shale, conglome

siltstone and mudstone wit

sandstone

siltstone, sandstone,and lim

arkosic sandstone, siltstone

limestone, dolomite, sands

granite, quartz monzonite, 
Tertiary basalt 

Tertiary sedimentary rocks 

Cretaceous Mesaverde Formation 

Cretaceous Mancos Formation

39C

Kmv

0 10 Miles

Figure 2. Generalized geologic map of the Grand Mesa National Forest (after Tweto, 1979).
108°

- 38

LJ Tertiary basalt

D Tertiary ash-flow tuff

H Tertiary quartz latite

I Tertiary andesite

I Cretaceous Mancos Formation

I Mesozoic sedimentary rocks

I Paleozoic sedimentary rocks

| Tertiary intrusive and Precambrian rocks

10 Miles

Figure 3. Generalized geology (after Tweto, 1979) of the Uncomphagre National Forest.
conglomerate, shale, and limestone, Mississippian Leadville Limestone and Devonian Ouray 

Limestone, and Elbert Formation of limestone, dolomite, arkosic sandstone, conglomerate, and 

shale and Tertiary and Proterozoic intrusive rocks and Proterozoic metamorphic rocks.

The major rock types within the Gunnison National Forest (fig. 4) consist of Pliocene to 

Miocene basalt flows and associated tuff, breccia, and conglomerate, Oligocene ash-flow tuff, 

Oligocene inter-ash flow quartz latitic lava and breccia, Oligocene andesitic lava and breccia, 

Oligocene Duchesne River Formation of sandstone and shale, Eocene and Paleocene Wasatch 

and Ohio Creek Formations of claystone, mudstone, sandstone, and conglomerate, Cretaceous 

Mesaverde Formation of sandstone and shale with coal beds, Cretaceous Mancos Shale of 

sandstone, shale, and conglomerate, Permian and Pennsylvanian Maroon Formation of arkosic 

sandstone, siltstone, conglomerate, and limestone, Pennsylvanian Minturn and Belden 

Formations of arkosic sandstone, shale, conglomerate, and limestone, Mississippian Leadville 

Limestone, Mississippian and Devonian Chaffee Group, Ordovician Fremont Limestone, 

Harding Sandstone and Manitou Dolomite, and Cambrian Sawatch Quartzite and Peerless 

Formation of limestone, dolomite, arkosic sandstone, shale, limestone, dolomite, ardosic 

sandstone, conglomerate and conglomerate and Tertiary and Proterozoic intrusive rocks and 

Proterozoic metamorphic rocks. The major rock types of the three National Forests are divided 

into ten dominant rock composition types (Table 2) and represent in some cases one rock 

formation such as the Mesavede Formation, or a group such as Cretaceous, Jurassic and Triassic 

sedimentary rocks of similar composition. The dominant rock types are: 1) Tertiary basalt flows 

and associated rocks; 2) Tertiary ash-flow tuff; 3) Tertiary quartz latitic lava and breccia; 4) 

Tertiary andesitic lavas and associated rocks; 5) Tertiary sedimentary rocks; 6) Cretaceous 

Mesavede Formation; 7) Cretaceous Mancos Shale; 8) Mesozoic sedimentary rocks consisting of 

Cretaceous, Jurassic, and Triassic sedimentary rocks of predominantly sandstone; 9) Paleozoic 

sedimentary rocks; and 10) Proterozoic and Tertiary plutonic rocks and Proterozoic gneiss, and 

schist. The ten dominant rock compositional types represent most of the rocks (>95%) within 

the three National Forests.

Methods

Generally small streams were sampled, usually with a watershed area of around several 

square miles, although some watersheds are larger. Springs within the watershed were also 

sampled. Both stream and spring sites were chosen to represent each of the ten major rock 

composition types within the three National Forests.

Samples of water were collected from stream and spring sites within the study area during 

July and August, 1998 and August, 1999. The waters were collected after runoff had occurred

8
I

39° -

10 Miles

Tertiary basalt

Tertiary ash flow tuff 

Tertiary qurartz latite 

Tertiary andesite

Tertiary sedimentary rock

Cretaceous Mesaverde 

Formation

Cretaceous Mancos Formation

Mesozoic sedimentary 

rocks

Paleozoic sedimentary 

rock

Tertiary intrusive and 

Precambrian rocks

Figure 4. Generalized geology (after Tweto, 1979) of the Gunnison National Forest.

9
but prior to the streams reaching base flow or in some cases, drying up completely. Waters from 

areas underlain by each major rock composition type were usually collected within one or two 

days. Waters from areas of lower elevations were collected earlier in the season than the high 

alpine areas. During the time of sampling, the weather was stable and no precipitation occurred. 

Samples were collected by width and depth integration (Edwards and Glysson, 1988) or from a 

point source for springs. Temperature, pH, and conductivity were measured at the site. An 

Orion model 250 pH meter was used with an Orion Ross Sure-Flow electrode. The conductivity 

was measured using an Orion model 120 conductivity meter. Samples were collected into highdensity polyethylene bottles. For the dissolved cation analyses, a sample was filtered at the site 

through a 0.45 [im-membrane filter and acidified with ultrapure reagent-grade Ultrex nitric acid 

to pH < 2. Another sample was filtered but not acidified for anion analyses and an unfiltered, 

unacidified sample was collected for alkalinity measurement. The samples were stored in an ice 

chest and later in a refrigerator and kept cool until analyzed.

Upon return to the laboratory, alkalinity as HCO3~, was determined by titration with 

H2SO4 using Gran's plot technique (Orion Research, Inc., 1978). Sulfate, chloride, nitrate, and 

fluoride concentrations were determined by ion chromatography (1C) (Fishman and Pyen, 1979). 

Cations were analyzed by inductively coupled plasma - atomic emission spectromentry (ICPAES) or inductively coupled plasma - mass spectromentry (ICP-MS). 1C, ICP-AES, and 

alkalinity analyses were performed by Murdock Environmental Laboratory, University of 

Montana, Missoula, The ICP-MS analyses for samples collected in 1998 were determined by 

ACTLABS, Wheatridge, CO. The samples collected in!999 were determined by U.S.G.S. 

laboratories under the direction of Paul Lamothe. The ICP-AES analyses for samples collected 

in 1998 were determined by Murdock Environmental Laboratory. The samples collected in 1999 

were determined by U.S.G.S. laboratories under the direction of Paul Briggs. Duplicate water 

samples, blank samples, and USGS Water Resource Division standard reference waters were 

analyzed with each data set. The chemical analyses are shown in appendix 1.

Results

Water samples were collected from small streams or springs of watersheds that were 

within or mainly within the three National Forests. The watersheds are mountainous headwaters 

and are not impacted by historic mining. Cattle is grazed in some of the watersheds which may 

have some impact on water quality. The samples were selected so that the geochemical baseline 

chemistry approximates the natural background geochemistry as closely as possible for each of 

the ten rock compositional types (Table 2) that are dominant in the three National Forests. The 

ranges and means of species and other parameters were determined for waters from areas

10
Table 2. The ten dominant rock compositon types in the Gunnison, Grand Mesa, and Uncompahgre N

Period ROCK Composition Type 

Tertiary 

Tertiary 

Tertiary 

Tertiary 

Tertiary

Cretaceous 

Cretaceous 

Mesozoic 

Paleozoic

Tertiary

and Proterozoic

basalt flows and associated rocks

felsic ash flow tuff

quartz latitic lava and breccia

andesitic lava, breccia, and tuff

Tertiary sedimentary rocks of shale, oil shale, sandstone, marlstone,

claystone, and lignite

Mesaverde Formation of sandstone, shale, coal, minor intrusive

rock, and claystone

Mancos Formation of marine shale, sandstone, and calcareous

sandstone

Mesozoic sedimentary rocks of sandstone, siltstone, shale, limestone,

conglomerate, and mudstone

Paleozoic sedimentary rocks of sandstone, conglomerate,

carbonate, quartzite, shale, mudstone, grit

granite, quartz monzonite, felsic and hornblende gneiss

Grand M

San Jua

San Jua

West Elk 

Battleme

Piceanc

San Jua

Uncomp

West fla

Sawatch 

scattere
underlain by each of the dominant rock composition types. 

Tertiary basalt flows and associated rocks

Water samples were collected from four small streams draining areas underlain by 

Pliocene and Miocene basaltic lava, tuff, breccia, and conglomerate from the top of Grand Mesa 

in the Grand Mesa National Forest (fig. 5). The ranges and means of selected species in the 

waters are shown in Table 3. The complete chemical analyses of these sites and the remaining 

sites are shown in appendix 1. Grand Mesa rises more than a mile above the surrounding 

valleys. The basaltic rocks overlie the Tertiary Green River, Wasatch, and Ohio Creek 

Formations. Relief on the top of Grand Mesa is low. The area receives 30 to 45 inches of annual 

precipitation (Colorado Climate Center, 1984), and snow pack can range from 5 to 10 feet. 

Vegetation is mainly sub-alpine forest and grasslands. The sites contain dilute Ca2+- HC03" type 

waters with slightly alkaline pH values and moderate to low alkalinity values. Mean pH is 7.41 

and mean conductivity is 63 [iS/cm. The mean Cl concentration is 0.29 mg/1, indicating much of 

the water is snow melt with minimal time of contact with the rocks. Cl concentration is 

conservative and a good indicator of evaporation effects. All species are low in concentrations, 

except for Al. Mean Al concentration is 54 ug/1, probably because the initial low pH values of 

the melting snow is favorable for the mobility of Al. Generally, waters that are in contact with 

basaltic rocks are well buffered with moderate values of alkalinity. But the short time of contact 

of the melting snow with the basaltic rocks on Grand Mesa only allows the waters to pick up 

moderately low alkalinity values. Alkalinity ranges from 24 to 30 mg/1 as HCO3" with a mean of 

28 mg/1. This low mean value suggests that the top of Grand Mesa is moderately susceptible to 

introduced acidification. Introduced acidity from sources such as acid rain could consume the 

alkalinity in waters, causing the streams and lakes on the top of Grand Mesa to become acidic. 

Except for moderate amounts of Al, the waters from Grand Mesa are excellent in water quality.

Tertiary ash-flow tuff

Water samples were collected from three streams and two springs in the Los Pinos Creek 

and Pauline Creek watersheds in areas underlain by Oligocene rhyolitic ash-flow tuff in the 

Gunnison National Forest (fig. 6). The sources of the tuff are calderas in the San Juan Mountains 

to the south. The relief in the area is high and the dominant vegetation is subalpine forest. 

Annual precipitation ranges from 16 to 30 inches (Colorado Climate Center, 1984). The ranges 

and means of selected species in the waters are shown in Table 4. The sites contain Ca2+- HCO3" 

type waters with slightly acidic to slightly alkaline pH values and moderately low conductivities.

12
- 39 00

Top of Grand Mesa

108° 7'30"

Figure 5. Site locations of stream waters from areas underlain by Tertiary 

basalt flows and associated rocks, Grand Mesa National Forest.

13
Table 3. Stream waters from watersheds underlain by Tertiary basalt flows, tuff, breccia, 

and conglomerates (n+4)

Measurement1 Range Mean2

Minimum Maximum

Conductivity

PH

Ca

Mg

Na

K

SiO2

Alkalinity

SO4

Cl

F

Al

Fe

Mn

Cu

Zn

Pb

Mo

Sb

As

Th

U

Li

Ba

Sr

V

Sc

Rb

Y

Zr

La

Br

I

59

7.09

4

1.8

1.5

0.24

11

24

0.38

<0.25

<0.1

38

44

4.2

<1

0.32

<0.1

<0.5

<0.01

<0.03

0.069

0.036

<0.5

10

29

<0.5

17

0.29

0.31

0.28

0.17

<3

<0.2

66

7.67

6.1

2.3

2

0.45

19

30

1.6

0.6

<0.1

107

151

27

<1

0.52

1.4

0.53

0.22

0.67

0.1

0.15

<0.5

17

39

0.57

26

1.3

0.53

1

0.31

<3

20

63

7.41

5.4

2.1

1.8

0.37

14

28

0.65

0.29

<0.1

54

91

15

<1

0.4

0.15

<0.5

0.017

0.048

0.083

0.069

<0.5

14

36

<0.5

21

0.5

0.41

0.43

0.25

<3

0.98

1 Ca, Mg, Na, K, SiO2, SO4, Cl, and F in mg/l, alkalinity in mg/l HCCb, 

Conductivity in uS/cm, remaining elements in ug/l.

2 All variables are geometric means except for pH which is arithmatic mean.

14
h 38° 7' 30"

 Stream site 

cr- Spring site

106° 52'30" 

___I___

'U '

j McDonough j 

Resv. ._.__._; 

l

. . . j

Gunnison National 

46 Forest

56

1 Mile

Figure 6. Site locations of stream and spring waters from areas 

underlain by Tertiary ash-flow tuff in the Los Pinios and 

Pauline Creek watersheds, Gunnison National Forest.

15
Table 4. Stream waters from watersheds underlain by Tertiary ash-flow tuff (n=5)

Measurement1 Range Mean2

Minimum Maximum

Conductivity

PH

Ca

Mg

Na

K

SiO2

Alkalinity

SO4

Cl

F

Al

Fe

Mn

Cu

Zn

Pb

Mo

Sb

As

Th

_ U

Li

Ba

Sr

V

Sc

Rb

Y

Zr

La

Br

I

57

6.89

5.3

0.83

3.1

0.87

19

32

1.4

0.37

<0.1

6.7

9.5

<0.3

<1

<0.2

<0.1

<0.5

<0.01

0.79

0.07

0.012

0.86

10

47

<0.5

22

0.3

0.047

0.12

<0.005

<3

<0.2

139

8.02

16.5

2.8

7.9

2.3

41

70

6

1.9

0.14

-34

640

32

<1

0.32

1.1

0.6

0.13

2.2

0.57

0.2

2.8

32

109

3.4

51

3.1

0.18

19

0.17

33

7.8

100

7.43

11

1.7

4.4

1.3

29

46

2.7

0.88

0.1

16

65

2.9

<1

0.24

0.12

<0.5

0.021

1.2

0.19

0.058

1.5

18

79

1.2

35

1.2

0.1

0.51

0.024

3.5

2.2

1 Ca, Mg, Na, K, SiG>2, SO4 , Cl, and F in mg/l, alkalinity in mg/l HCOa, 

conductivity in uS/cm, remaining elements in ug/l

2 All variables are geometric means except for pH which is arithmatic mean.

16
Mean pH is 7.43 and mean conductivity is 100 [iS/cm. Mean Zn is very low at 0.24 [ig/1 and Cu 

at <0.1 |ig/l. SiO2 concentrations ranged from 19 to 41 mg/1 with a mean of 29 |ig/l. These 

higher concentrations of SiO2 are probably because of the felsic rock composition and the finegrain size of the minerals which compose the rocks are more susceptible to weathering. 

Alkalinity values ranged from 32 to 70 mg/1 as HCO3" with a mean of 46 mg/1. This moderately 

low value is mainly because the felsic composition rocks do not weather as rapidly as more mafic 

rocks. Mean Cl content is 0.88 mg/1, which is low and reflects the short residence time of the 

melting snow and rain in contact with the rocks and lack of significant evaporation. Two stream 

waters were high in Fe concentrations with 255 and 640 [ig/1 respectively. Both sites were 

contaminated by cattle wastes and were slightly yellow brown in color. The wastes probably 

caused more reducing conditions which favors the mobility of Fe. Another possibility for the Fe 

mobility may be due to Fe complexing with organic matter. Except for the Fe concentrations in 

the two samples, the waters in the watersheds underlain by the Tertiary ash-flow tuff are of good 

chemical quality. The felsic rock type and the short contact time of the water and rock favor 

moderately low alkalinity. The moderately low alkalinity values make the area moderately 

susceptible to introduced acidification. Moderate amounts of acidification from mining or 

atmospheric precipitation could consume the alkalinity and cause the stream waters to become 

acidic.

Tertiary quartz latitic lava and breccia

Samples of water were collected from four streams in the Mineral Creek drainage in the 

northern part of the San Juan volcanic field in the La Garita Wilderness, Gunnison National 

Forest (fig. 7). The area is underlain by Oligocene inter-ash flow quartz latitic lava and 

breccia.(Tweto and others, 1976). Relief is high and the dominant vegetation is subalpine forest. 

Annual precipitation ranges from 16 to 25 inches (Colorado Climate Center, 1984). The ranges 

and means of selected species in the waters are shown in Table 5. The sites contain three Ca2+- 

HCO3" and one Na+- HCO3" type waters with slightly alkaline pH values and moderately low 

conductivities. Mean pH is 7.48 and mean conductivity is 124 [iS/cm. Trace metal 

concentrations are low. Mean Zn, Cu, Mo, and As are 0.5, 0.56 , 0.54, and <3 |ig/l, respectively. 

The range of SiO2 concentrations is 20 to 56 mg/1 with a mean of 31 mg/1. The higher values are 

probably due to the felsic composition of the rocks and the fine-grain size of the rock minerals 

with high surface areas, which favor chemical dissolution of the silicates. The mean 

concentrations of Al and Fe are moderately high with means of 60 and and 55 [ig/1 respectively, 

The concentration of Mn is low with a mean of 2.7 [ig/1. The mean Cl concentration is 0.56 

mg/1, which is low and reflects the short residence time of the water from melting snow and rain

17
Gunnison National 

Forest

IMile

107°02' 30" 

I

38°

Figure 7 . Site locations of stream waters collected from areas underlain by 

intra-ash-flow quartz latite lavas, in the Mineral Creek watershed, 

Gunnison National Forest.

18
Table 5. Four stream waters from watersheds underlain by Oligocene quartz latitic 

lava and breccia

Measurement1

Conductivity

PH

Ca

Mg

Na

K

SiO2

Alkalinity

SO4

Cl

F

Al

Fe

Mn

Cu

Zn

Pb

Mo

Sb

As

Th

U

Li

Ba

Sr

V

Sc

Rb

Y

Zr

La

Range

Minimum

108

7.35

8.7

0.78

3.7

0.69

20

29

10

O.25

<0.1

7.9

33

1

<0.5

<0.5

O.05

0.3

0.1

<3

O.005

0.08

1.7

2.6

58

0.8

1.9

0.9

0.1

0.08

0.05

Maximum

140

7.75

16

2.9

13

2.2

56

44

28

1.5

<0.1

356

159

21

0.8

1

O.05

1

0.2

<3

0.15

0.32

10

13

171

1.6

5.3

3

1.5

1.4

0.5

Mean2

124

7.48

12.6

1.8

6.9

1.1

30.8

36

16.6

0.56

<0.1

55

60

2.7

0.56

0.5

O.05

0.54

<0.1

<3

0.03

0.14

3.6

4.6

115

1.1

2.9

1.4

0.32

0.32

0.13

1 Ca, Mg, Na, K, SiO2, SCU, Cl, and F in mg/l, alkalinity in mg/l HCOs, 

conductivity in uS/cm, remaining elements in ug/l

2 All variables are geometric means except for pH which is arithmatic mean.

19
in contact with the rocks and the lack of significant evaporation. The alkalinity as HCO3" ranged 

from 29 to 44 mg/1 with a mean of 36 mg/1, which indicates weakly acid- neutralizing capacity. 

The felsic rock type and the short contact time of the water and rock favor moderately low 

alkalinity values. Because of the moderately low alkalinity values, the areas underlain by quartz 

latitic rocks are moderately susceptible to introduced acidification. Moderate amounts of 

acidification could consume the alkalinity and cause the stream waters to become acidic. The 

chemical quality of the waters from watersheds underlain by Tertiary quartz latitic rocks is good.

Tertiary andesitic rocks

Water samples were collected from eight streams in the Soap Creek area of the West Elk 

Mountains, Gunnison National Forest (fig. 8). The area is underlain by Oligocene andesitic lava 

flow, tuff, breccia, and conglomerate. The andesitic rocks originated from the nearby West Elk 

volcanic centers. Relief is high and the dominant vegetation is subalpine forest. Annual 

precipitation ranges from 20 to 40 inches (Colorado Climate Center, 1984). The ranges and 

means of selected species in the waters are shown in Table 6. The area contains Ca2+- HCO3" 

type waters with alkaline pH values and moderate conductivities. Mean pH is 7.99 and mean 

conductivity is 158 |iS/cm. Trace element concentrations are low to very low. Mean Zn, Cu, 

Mo, and As are 0.22 jig/1, <1 [ig/1, <0.5 [ig/1, and 0.7 [ig/1, respectively. The range of SiO2 

concentrations is 22 to 48 mg/1 with a mean of 35 mg/1. The higher values are probably due to 

the fine-grain size of the rock minerals with high surface area, which favors dissolution of 

silicates. The mean concentrations of Al, Fe, and Mn are moderately low with means of 13, 16, 

and 0.48 [ig/1 respectively. The mean Cl concentration is 0.7 mg/1, which is low and reflects the 

short residence time of the waters from melting snow and rain in contact with the rocks and the 

lack of significant evaporation. The alkalinity as HCO3 ' ranged from 32 to 102 mg/1 with a mean 

of 72 mg/1, which indicates moderate acid- neutralizing capacity for introduced acidification. 

Even though the residence time of water and rock is short, the fine-grain minerals and the 

intermediate composition of the rocks ensure that the rate of chemical weathering is rapid. 

Therefore the waters of this area, underlain by Tertiary andesitic rocks, have moderate acidneutralizing capacity for introduced acidification. The chemical quality of the waters from 

watersheds underlain by Tertiary andesitic rocks is good.

Tertiary sedimentary rocks

Samples of water were collected from seven streams draining headwater watersheds 

underlain by Eocene Green River, Wasatch, and Ohio Creek Formations in the Grand Mesa

20
107 22 30

- 38° 37'30"

1 Mile

Gunnison National 

Forest

Blue Mesa Resv.

Figure 8. Site locations of stream waters from areas underlain 

by Tertiary andesites in the Soap Creek watershed, 

Gunnison National Forest.

21
Table 6. Eight stream waters from watersheds underlain by Oligocene andesitic 

lava and breccia

Measurment1

Conductivity

PH

Ca

Mg

Na

K

SiO2

Alkalinity

SO4

Cl

F

Al

Fe

Mn

Cu

Zn

Pb

Mo

Sb

As

Th

U

Li

Ba

Sr

V

Sc

Rb

Y

Zr

La

Br

I

Range

Minimum

104

7.49

10

1.6

4.8

0.81

22

32

0.76

0.34

<0.1

8.9

8.6

<0.3

<1

<0.2

<0.1

<0.5

<0.01

0.4

0.12

<0.001

0.79

1.5

60

0.8

26

1.4

0.05

0.15

<0.005

<3

<0.2

Maximum

242

8.53

22

7.7

15

2.4

48

102

23

1

0.14

21

31

4

<1

0.38

<0.1

0.59

0.074

1.3

0.37

0.28

2.9

9.2

149

2.9

54

3.7

0.11

0.45

<0.005

<3

2.2

Mean2

158

7.99

16

3

7.7

1.7

35

72

3.5

0.7

<0.1

13

16

0.48

<1

0.22

<0.1

<0.5

0.012

0.7

0.2

0.092

1.3

5

95

2.2

41

2.4

0.071

0.27

<0.005

<3

0.21

1 Ca, Mg, Na, K, SiO2, SO4, Cl, and F in mg/l, alkalinity in mg/l 

conductivity in uS/cm, remaining elements in ug/l

2 All variables are geometric means except for pH which is arithmatic mean.

22
National Forest (fig. 9). The Wasatch and Ohio Creek Formations were formed from detritus 

shed from the rising Rocky Mountains onto vast river flood plains and deltas flanking an 

immense lake (Bradley, 1964 and Roehler, 1974). The Green River Formation formed within the 

immense lake with large accumulations of plant and animal detritus, which resulted in oil shale 

(Bradley, 1964 and Roehler, 1974). Many of the sites were selected because of the presence of 

outcrops of the Parachute Member of the Green River Formation, which contains oil shale, in the 

sampled watersheds.

The watersheds are located along the flanks of Battlement Mesa and Grand Mesa. Relief 

ranges from moderate to high. The area receives from 20 to 35 inches of annual precipitation 

(Colorado Climate Center, 1984). The higher elevations receive the higher precipitation. 

Vegetation is mainly oak scrublands and subalpine forest in the higher areas. Some of the 

watersheds are physically impacted by cattle grazing with the increase in sediments in streams 

and the deterioration of wetlands from the hooves of cattle and accumulation of cattle wastes.

The ranges and means of selected species in waters are shown in Table 7. The sites all 

contain Ca2+- HCO3' type waters with alkaline pH values and moderately high conductivity 

values. The mean pH is 8.50 and the mean conductivity is 365 p,S/cm. Therefore the waters are 

moderately high in mean conductivity values for headwater watersheds. The waters are well 

buffered with mean alkalinity of 191 mg/1 as HCO3 ". Cl concentrations are conservative and a 

good indicator for evaporation effects. The mean Cl concentration is 1.4 mg/1. Background Cl 

for this area is probably less than 0.5 mg/1 in the absence of input of Cl from weathering of rocks. 

There may be some input of Cl from these rocks. Halite is known to be present in oil shale in the 

subsurface (Turtle, 1992). Some of the waters may have undergone evaporation and 

concentration in the soil and weathered rock zones and then input as groundwater along the 

stream channels. Mean concentration of SiO2 is 17.5 mg/1, which is slightly above the average 

background concentration for fresh water (Table 8). Cu, Zn, and other trace metals present as 

cations are very low in concentrations (< 1 M-g/1), even though the oil shale in the Green River 

Formation contains anomalous concentrations of trace metals (Harrison and others, 1992). The 

high pH values ensure that hydrolysis reactions keep the trace metal cations low in 

concentrations. This is not true with some of the trace species present as anions, which are 

slightly elevated in concentrations. Mean concentrations of Mo, As, and U are 1.9, 1.9, and 1.4 

jig/1, respectively. These values are high compared to average fresh water (Table 8). In addition, 

the elements I, Br, Li, and Sr are elevated in concentration compared to fresh water (Table 8). 

Even though these elements are elevated, particularly for head water watersheds, no element 

poses a problem for water quality.

Five of the streams that were sampled drain watersheds with outcrops of the Parachute 

member of the Green River Formation (appendix 1), which contains oil shale. Pyrite is present

23
- 39° 22' 30"

Grand Mesa 

National Forest

Grand Mesa National Forest 0 1 2 Miles

Figure 9. Site locations of steam waters from areas underlain by Eocene

Green River, Wasatch, and Ohio Creek Formations in the Buzzard 

Creek watershed, Grand Mesa National Forest.

24
Table 7. Waters from areas underlain by Tertiary Sediments of marlstone, oil shale, 

siltstone, claystone, mudstone, sandstone, and conglomerate (n=7).

Measurement1

Conductivity

PH

Ca

Mg

Na

K

Si02

Alkalinity

SO4

Cl

F

Al

Fe

Mn

Cu

Zn

Pb

Mo

Sb

As

Th

U

Li

Ba

Sr

V

Sc

Rb

Y

Zr

La

Br

I

Range

Minimum

195

8.16

18

6.6

5.2

0.65

6.5

92

3.4

0.63

<0.1

<3

<5

<0.3

<1

<0.2

<0.1

0.53

<0.01

0.62

0.18

0.39

1.3

32

114

1.3

11

0.4

0.05

0.14

<0.005

<3

<0.2

Maximum

652

8.69

62

37

45

3.8

27

352

25

8.3

0.51

24

36

171

1.7

0.53

2.9

7.5

0.29

5.8

1.5

8.8

25

208

718

5.5

36

0.84

0.17

1.3

0.072

182

36

Mean2

365

8.50

39

12

15

1.4

18

191

8.1

1.4

0.16

12

13

4.7

<1

0.22

0.18

1.9

0.12

1.9

0.36

1.4

7.2

62

311

2.8

25

0.6

0.083

0.42

0.017

6.6

1.5

1 Ca, Mg, Na, K, SiO2, SG>4, Cl, and F in mg/l, alkalinity in mg/l HCOa, 

conductivity in uS/cm, remaining elements in ug/l

2 All variables are geometric means except for pH which is arithmetic mean.

25
Table 8. Background of trace metals in freshwater and chemical analyses of mean river water.

____Background of trace metals in freshwater_____________ 

Element Data from Forstner and Wittmann (1979)

Al

Cr

Fe

Mn

Ni

Zn

Ag

Al

As

Au

B

Ba

Be

Cd

Co

Cr

Cu

Fe

Li

Mn

Mo

Ni

Pb

Sb

Se

Sr

Sn

Ti

U

V

Zn

<30

0.5

<30

<5

0.3

10

0.3

<30

2

0.01

10

10

0.01

0.07

0.05

0.5

1.8

<30

1

<5

1

0.3

0.2

0.1

0.1

50

0.03

<1

0.5

0.9

10

Chemical analyses of mean river water

Element in mg/l Data from Livingstone (1963)

Ca 15

Mg 4.1

Na 6.3

K 2.3

SiO2 13.1

SO4 11.2

HCO3 58.4

Cl 7.8

26
in the oil shale and will oxidize and release sulfate, trace metals contained in the pyrite, and 

acidity to the waters. The well buffered waters with high alkalinity values react and consume 

acidity release during the oxidation of pyrite, and the high pH values hydrolyze any trace metals 

carried as cations and reduce their mobility. Sulfate value, up to 25 mg/1, indicate that pyrite is 

weathering and sulfate is being released. There are some elevated As values, up to 5.8 |ig/l 

(appendix 1), probably from the weathering of pyrite, but overall there is no significant impact to 

the water quality of these headwater streams. The high alkalinity of the waters is probably due to 

the presence of marlstone. The marlstones are fine-grained and the calcite reacts rapidly, 

releasing carbonate species, mostly bicarbonate, to the waters. Because of the high alkalinity 

values, the watersheds underlain by these rock are not susceptible to introduced acidification 

from processes such as acid rain or acid-mine drainage. The waters evolving from the 

watersheds underlain by the Green River, Wasatch, and Ohio Creek Formations are moderately 

high in dissolved solids for headwater streams, but pose no human health risk in terms of 

chemical water quality.

Cretaceous Mesavede Formation

Water samples were collected from seven streams and one spring in the Coal Creek area 

along the northern flank-of the West Elk Mountains in the Gunnison National Forest (fig. 10). 

The ranges and means of selected species in water are shown in Table 9. The area containing the 

sample sites is underlain by Late Cretaceous Mesaverde Formation rocks. Minor amounts of 

Oligocene intermediate-composition intrusive rocks are also present in some watersheds. The 

Mesaverde Formation consists of mostly sandstone with some shale and coal beds. The rocks 

were deposited in sand beach, river delta, and swamp environments. The economically 

important low-sulfur bituminous coal beds resulted from accumulation of organic material in 

marshes and lagoons that formed behind sand-barrier islands (Benedict, 1991). The relief of the 

area is high and annual precipitation ranges from 20 to 35 inches (Colorado Climate Center, 

1984). Dominant vegetation is subalpine forest. The sites contain Ca2+- HCO3" type waters with 

alkaline pH values and moderate conductivity values. Values for pH ranged from 8.00 to 8.57 

with a mean of 8.31. Conductivity values ranged from 76 to 268 jiS/cm with a mean of 126 

jiS/cm. The mean Cl content is 0.49 mg/1, which suggests that no significant evaporation and no 

long term contact of the water with the rocks has taken place. A significant portion of the stream 

water is probably snow melt. The range in concentrations of SiO2 is 11 to 15 mg/1 with a mean 

of 13 mg/1, which is about average for fresh water (Table 8). The coarser grain size and the well 

crystallized nature of the silica minerals are probably the reason that the waters from areas 

underlain by sandstones contain less SiO2 than the finer grained size minerals of the ash-flow tuff

27
 Stream Site 

@ Spring Site

Gunnison National Forest

0 1 Mile

38 52' 30" -\

107 15'

Figure 10. Site locations of stream and spring waters from areas underlain 

by Cretaceous Mesaverde Formations in the Coal Creek and 

Snowshoe Creek watersheds, Gunnison Naional Forest.

28
Table 9. Eight waters from areas underlain by the Mesaverde Formation of sandstone, shale, 

and major coal beds

Measurement1

Conductivity

PH

Ca

Mg

Na

K

SiO2

Alkalinity

SO4

Cl

F

Al

Fe

Mn

Cu

Zn

Pb

Mo

Sb

As

Th

U

Li

Ba

Sr

V

Sc

Rb

Y

Zr

La

Br

I

Range

Minimum

76

8

7.7

1.3

3.8

0.32

11

34

1.5

0.25

<0.1

9

<5

1.4

<1

<0.2

<0.1

<0.5

<0.01

<0.03

O.002

0.077

0.72

11

52

<0.5

16

0.14

0.03

<0.05

0.005

<3

O.2

Maximum

268

8.57

31

8.3

13.4

0.81

15

122

19

1

0.75

27

30

7

<1

0.36

O.1

0.63

0.01

2.4

0.023

0.51

4.7

49

364

0.74

21

0.45

0.12

0.62

0.089

<3

O.2

Mean2

126

8.31

13

3

5.4

0.49

13

54

5.3

0.49

0.11

12

14

2

<1

0.24

O.1

0.5

O.01

0.08

0.003

0.13

1.4

18

189

O.5

18

0.32

0.042

0.15

0.005

<3

O.2

1 Ca, Mg, Na, K, SiO2, SO4, Cl, and F in mg/l, alkalinity in mg/l HCO3, 

conductivity in uS/cm, remaining elements in ug/l

2 All variables are geometric means except for pH which is arithmatic mean.

29
and andesitic rocks. The concentrations of trace elements Zn, Cu, Mo, and As are very low, with 

means of 0.24, <1, and <0.5, and <0.08 }j.g/l, respectively. Concentrations of Al, Fe, and Mn are 

also low in with means of 12, 14, and 2 }j.g/l, respectively. Alkalinity values range from 34 to 

122 mg/1 as HCO3" with a mean of 54 mg/1. This wide range in alkalinity values may be due to 

the presence of pyrite associated with the coal beds. Weathering of pyrite releases acid to the 

waters, which consumes alkalinity. The moderately low mean alkalinity suggests low to 

moderated acid-neutralizing capacity of the watershed to introduced acidification. Overall the 

water quality of the area is good to excellent.

Cretaceous Mancos Shale

Water samples were collected from two areas underlain by the Mancos Shale. Six 

streams were sampled in the southwestern part of the Uncompahgre National Forest in the area of 

McCulloch, Beaver, and Goat Creek (fig. 11). Two springs were sampled along the northwestern 

flank of the West Elk Mountains in the area of Bell Creek in the Gunnison National Forest (fig. 

12). The ranges and means of selected species in water are shown on Table 10. The Cretaceous 

Mancos Shale consists of silty and sandy shale and thin bedded sandstone with calcareous zones 

deposited in a marine setting. The two areas are of high relief and annual precipitation ranges 

from 16 to 40 inches (Colorado Climate Center, 1984). Dominant vegetation in both areas is 

subalpine forest, but in lower areas outside the National Forest, badland topography with sparse 

scrub vegetation is present. The sites all contain Ca2+- HCO3 " type waters with alkaline pH 

values and moderately high conductivity values. Values of pH range from 7.46 to 8.58 with a 

mean of 8.20. Conductivity values range from 107 to 401 [j.S/cm with a mean of 258 [j.S/cm. 

The mean Cl content is 0.6 mg/1, which suggests that evaporation and time of contact of the 

waters with rocks and soils is not significant. It is possible that some of the Cl may come from 

the weathering of the rocks, but the low concentration of Cl suggests that this process is 

insignificant. Note that these sites are in higher elevation areas and do not necessarily reflect the 

processes that are going on in the lower elevation, less-vegetated areas underlain by the Mancos 

Shale outside the National Forests. Mean concentrations of SiO2 is 13 mg/1 which is about 

average for fresh water (Table 8). Concentrations of trace elements are mainly low with mean 

Zn, Cu, Mo, and As values of 0.21, <1, 0.71, and 0.12 |ig/l, respectively. One reason for high 

concentrations of Se in waters in the lower valleys is thought to be due to high Se concentrations 

in the Mancos Shale. In these headwater watersheds underlain by the Mancos Shale, Se 

concentrations in waters are all <0.2 }j.g/l. The high Se concentrations in the lower valleys are 

probably due to evaporation effects from natural processes and irrigation. Se, similar to Cl, will 

concentrate with evaporation. The concentrations of Al, Fe, and Mn are low at 10, 15, and 2.2

30
Uncompahgre National 

Forest

31

108° 07'15" 

I

Figure 11. Site-locations of stream waters from areas underlain by Cretaceous 

Mancos Formation in the Beaver and Goat Creek watersheds, 

Uncompahgre National Forest.

31
Roeber Resv.

107°32'

O

19 Gunnison National 

Forest

38°48' 

1 Mile

Figure 12. Site locations of spring waters from areas underlain by Cretaceous Mancos 

Formation in the Bell Creek area, Gunnison Naional Forest.

32
Table 10. Ten waters from areas underlain by Mancos Shale of shale, calcarous shale 

and sandstone

Measurement1

Conductivity

PH

Ca

Mg

Na

K

Si02

Alkalinity

SO4

Cl

F

Al

Fe

Mn

Cu

Zn

Pb

Mo

Sb

As

Th

U

Li

Ba

Sr

V

Sc

Rb

Y

Zr

La

Br

1

Range

Minimum

107

7.46

12

2.3

2.5

0.15

8.6

30

6.1

0.26

<0.1

4.5

<5

<0.3

<1

<0.2

<0.1

<0.5

<0.01

<0.03

0.02

0.12

<0.5

4.8

39

<0.5

14

0.052

0.034

<0.05

<0.005

<3

<0.2

Maximum

401

8.58

50

13

13

1

27

180

37

1.9

0.19

16

60

29

<1

0.47

<0.1

1.7

0.14

0.48

0.062

0.58

5.9

35

581

1.7

35

0.65

0.13

0.42

<0.005

<3

3.9

Mean2

258

8.20

32

7.5

4.7

0.36

13

101

18

0.6

0.12

10

15

2.2

<1

0.21

<0.1

0.71

0.015

0.12

0.032

0.27

1.6

18

169

0.43

19

0.16

0.053

0.067

O.005

<3

0.51

T Ca, Mg, Na, K, SiO2, SG>4, Cl, and F in mg/l, alkalinity in mg/l HCO3 , 

conductivity in uS/cm, remaining elements in ug/l 

2 All variables are geometric means except for pH which is arithmatic mean.

33
|ig/l, respectively. Alkalinity values are moderately high and ranges from 30 to 180 mg/1 as 

HCO3" with a mean of 101 mg/1. The moderately high alkalinity is probably due to the presence 

of calcareous zones in the unit. These values of alkalinity suggest that the waters of mountainous 

headwater areas underlain by the Mancos Shale have moderate acid-neutralizing capacity to 

introduced acidification. Except for the moderately high dissolved solid content, the water 

quality is good.

Mesozoic sedimentary rocks

Waters were collected from .one stream and four springs along the top and eastern flank of 

the Uncompahgre Plateau in the Uncompahgre National Forest (fig. 13). The ranges and means 

of selected species in water are shown in Table 11. The area is underlain by Cretaceous, 

Jurassic, and Triassic sedimentary rocks. Dominant units include Cretaceous Dakota Group and 

Burro Canyon Formation, Jurassic Summerville Formation, Entrada Sandstone, and Morrison 

Formation, and Triassic Wingate and Chinle Formation (Tweto, 1979). The rocks are mostly 

sandstone, siltstone, mudstone, and conglomerate. The rocks are dominantly terrestrial in origin 

and are mostly fluvial, but dune, flood-plain, and lacustrine deposits also occur. Many of the 

rocks were deposited during warm dry conditions. A few rocks of marine origin are included and 

consist of shale and limestone. Several of the units, such as the Morrison, Entrada, and Chinle 

Formations, contain uranium and vanadium deposits, particularly along the western flank of the 

Uncompahgre Plateau outside of the Uncompahgre National Forest. Impure coal beds are 

present in the Dakota Group. Relief ranges from moderate along the top to high along the flanks 

of the plateau. Annual precipitation ranges from 16 to 25 inches (Colorado Climate Center, 

1984). Dominant vegetation is mainly subalpine forest, although scrublands occur along the 

lower slopes.

The sites contain Ca2+- HCO3" type waters with alkaline pH values and moderately high 

conductivity values. The range in pH values is 7.48 to 8.53 with a mean of 7.94. The range in 

conductivity values is 299 to 527 |iS/cm with a mean of 413 |iS/cm. Mean Cl concentration is 

3.5 mg/1, suggesting that waters have been in contact with rocks and some evaporation and 

concentration has taken place. Four of the samples are groundwater from springs. Mean SiO2 

concentration is 10.9 mg/1, which is low compared to average fresh water (Table 8), probably 

because of the larger grain size and well crystallized mineral grains which make up many of the 

units such as the sandstone. The mean concentrations of trace elements Zn, Cu, Mo, and As are 

low at 0.23, <1, <0.5, and 1.2 |ig/l, respectively, but the mean concentrations of U and As are 

elevated at 2.7 and 1.2 |ig/l, respectively. Uranium and vanadium deposits are present in some of 

the rock units, particularly along the western flank of the Uncompahgre Plateau, mainly outside

34
I I

108° 37'30" i

- 38° 45'

Uncompahgre 

National Forest

i. _

Cold Springs 

Ranger Sta.

0 12

13

O Spring Site 

 Stream Site

Uncompahgre Butte 0 1 Mile

Figure 13. Site locations of stream and spring waters from areas underlain by 

Mesozoic sedimentary rocks along the top and east flank of the 

Uncompahgre Plateau, Uncompahgre National Forest.

35
Table 11. Five waters from Mesozoic sedimentary rocks of sandstone, mudstone, 

siltstone, shale, limestone, and conglomerate

Measurement1

Conductivity

PH

Ca

Mg

Na

K

Si02

Alkalinity

S04

Cl

F

Al

Fe

Mn

Cu

Zn

Pb

Mo

Sb

As

Th

U

Li

Ba

Sr

V

Sc

Rb

Y

Zr

La

Br

I

Range

Minimum

299

7.48

43

7.4

2

1.3

6.9

152

2.5

1.6

<0.1

<3

<5

<0.3

<1

<0.2

<0.1

<0.5

<0.01

0.33

0.045

1.4

7.9

227

161

<0.5

11

1.5

<0.03

<0.05

<0.005

<3

<0.2

Maximum

527

8.53

84

14

15

2.8

19

262

7.9

6.1

0.15

18

25

3.9

1

0.29

1.7

0.65

0.086

2.8

0.094

5.8

20

439

535

2.7

25

4

0.2

0.44

0.064

78

5.5 '

Mean2

413

7.94

59

10

5.2

1.8

10.9

205

4.7

3.5

0.12

6.7

4.6

0.68

<1

0.23

0.13

<0.5

0.019

1.2

0.07

2.7

12

286

241

0.68

15

2.4

0.035

0.14

0.005

8

0.98

1 Ca, Mg, Na, K, SiO2 , SO4, Cl, and F in mg/l, alkalinity in mg/l HCO3 , 

conductivity in uS/cm, remaining elements in ug/l 

2AII variables are geometric means except for pH which is arithmatic mean.

36
the National Forest. The mean concentrations of Al, Fe, and Mn are low at 6.7, 4.6, and 0.68 

(ig/1 respectively. Alkalinity values are high and range from 152 to 262 mg/1 as HCO3~ with a 

mean of 205 mg/1. The high alkalinity values are probably because of the presence of fine-grain, 

poorly crystallized calcite in marlstones, lacustrine deposits and as cements in sandstones. The 

high alkalinity values ensure that the waters from this area have good acid-neutralizing capacities 

to introduced acidification. Overall the waters are moderately high in total dissolved solids for 

headwater areas, but otherwise are of good chemical quality.

Paleozoic sedimentary rocks

Waters were collected from 14 streams and one spring in the Cement Creek and Spring 

Creek drainages along the western flank of the Sawatch Range, Gunnison National Forest (fig. 

14). The ranges and means of selected species in water are shown in Table 12. The area is 

underlain by Paleozoic sedimentary rocks. Dominant units include Permian and Pennsylvanian 

Maroon Formation, Pennsylvanian Minturn and Belden Formations, Mississippian Leadville 

Limestone, Williams Canyon Formation, and Manitor Limestone, and Cambrian Sawatch 

Quartzite (Tweto, 1976). The rocks are mostly limestone, dolomite, arkosic sandstone, 

conglomerate, and shale. Relief is high and annual precipitation ranges from 25 to 40 inches 

(Colorado Climate Center, 1984). Dominant vegetation is mainly subalpine forest.

The sites contain 14 Ca2+- HCO3 " and one Ca2+- SO42 " type waters with alkaline pH 

values and high conductivity values. The range in pH is 7.97 to 8.59 with a mean of 8.30. The 

range in conductivity values is 225 to 659 (aS/cm with a mean of 356 (iS/cm. Mean Cl 

concentration is O.25 mg/1, which is low and reflects the short residence time of the water from 

melting snow and rain in contact with the rocks and the lack of significant evaporation. Mean 

SiO2 concentration is 6.3 mg/1 which is low compared to average fresh water (Table 8), probably 

because of the larger grain size and well crystallized mineral grains of the silicate minerals and 

the abundance of carbonate minerals. The sulfate concentrations range from 0.85 to 204 mg/1, 

with a mean of 13.5 mg/1. Seven sites had sulfate concentrations > 30 mg/1 and two sites had 

concentrations >100 mg/1. The high concentrations of sulfate are probably due to the dissolution 

of gypsum present in the Permian and Pennsylvanian rocks. The Evaporite Facies to the north of 

the Gunnison National Forest contains gypsum and intertongues with the Minturn and Lower 

Maroon Formations (Tweto, 1976). The sites with sulfate >100 mg/1 are from drainages within 

these units. The mean concentrations of trace elements Zn, Cu, Mo, and As are low at 0.6, <0.5, 

<0.41, and <3 p,g/l, respectively. The mean concentrations of Al, Fe, and Mn are low at 0.34, 

<20, and 0.6 (ig/1 respectively. Alkalinity values are high and range from 110 to 194 mg/1 as 

HCO3 " with a mean of 143 mg/1. The moderately high alkalinity values are probably because of

37
C07

Gunnison National

Forest

38° 52' 30

I

1 Mile

106°45' 

__I

Figure 14. Site locations of stream and spring waters collected from watersheds underlain 

by Paleozoic sedimentary rocks in the Cement Creek watershed, Gunnison 

National Forest.

38
Table 12. Fourteen stream waters and one spring water from watersheds underlain 

by Paleozoic sedimentary rocks

Measurement1

Conductivity

PH

Ca

Mg

Na

K

SiO2

Alkalinity

SO4

Cl

F

Al

Fe

Mn

Cu

Zn

Pb

Mo

Sb

As

Th

U

Li

Ba

Sr

V

Sc

Rb

Y

Zr

La

Range

Minimum

225

7.97

40.6

2.94

0.61

0.11

3.7

110

0.85

<0.25

<0.1

0.77

<20

0.1

<0.5

<0.5

<0.05

<0.25

<0.01

<3

O.005

O.001

0.6

54

26

0.7

0.6

0.5

<0.01

<0.05

<0.01

Maximum

659

8.59

101

25

5.4

1.3

12

194

204

1.7

0.2

7.7

61

29

0.7

4.7

<0.05

1.5

0.2

<3

0.02

1.2

15

264

107

1.8

1.3

3.1

0.1

<0.05

0.02

Mean2

356

8.30

52.6

11

1.3

0.47

6.31

143

13.5

<0.25

<0.1

0.34

<20

0.6

<0.5

0.6

<0.05

0.41

<0.1

<3

0.01

0.56

2.1

88.5

107

0.9

0.9

0.47

0.03

<0.05

<0.01

1 Ca, Mg, Na, K, SiO2, SO4, Cl, and F in mg/l, alkalinity in mg/l HCOs, 

conductivity in uS/cm, remaining elements in ug/l

2 All variables are geometric means except for pH which is arithmatic mean.

39
the presence of abundant carbonate rocks and carbonate cement of some of the clastic rocks. The 

moderately high alkalinity values ensure that the waters from this area have good capacities to 

neutralize effects from introduced acidification. Overall the waters are moderately high in total 

dissolved solids, but otherwise are of good chemical quality.

Tertiary and Proterozoic intrusive rocks and Proterozoic metamorphic rocks

Water samples were collected from seven streams and one spring along the western flank 

of the Sawatch Range in the Quartz Creek area (fig. 15) and Tomichi Creek area (fig. 16) in the 

Gunnison National Forest. The ranges and means of selected species in water are shown in Table 

13. The areas are underlain by Proterozoic granites and felsic and hornblende gneiss and 

Oligocene stocks and dikes. The Proterozoic rocks are a basement complex of mainly 

metamorphic gneiss which has been intruded by granitic rock. Most of the rocks are felsic in 

composition and all are considered together as one group. The areas are of high relief and annual 

rainfall ranges from 16 to 35 inches (Colorado Climate Center, 1984). Vegetation is mainly 

subalpine forest. The sites all contain dilute Ca2+- HCO3" type waters with slightly acidic to 

alkaline pH values. Values of pH range from 6.89 to 8.18 with a mean of 7.82. Conductivity 

values are low and range from 47 to 126 fiS/cm with a mean of 83 fiS/cm. The mean Cl 

concentration is 0.39 mg/1, which suggests that the waters, which contain significant snow melt, 

are in short contact with the rocks, as would be expected for these dominantly crystalline rocks, 

with poorly developed soil zones and poor reserves of groundwater. In addition, the felsic rock 

composition and the well crystallized nature of the minerals ensure that chemical weathering is 

slow. Mean SiO2 concentration is 14 mg/1 and is about average for fresh water (Table 8). Even 

though the rocks are felsic in composition, the medium to coarse grain size and the well 

crystallized nature of the rock minerals, ensure that the SiO2 concentrations in waters are not 

higher. Sulfate concentrations range from 1 to 15 mg/1 with a mean of 3.5 mg/1. The higher 

values of some waters (appendix 1) are probably due to oxidation of pyrite present in areas of 

weakly mineralized rocks. Mines are present in the area, but no significant mining is present in 

the sampled watersheds. The mean concentrations of Cu and As are low at <1 and <0.03 fig/1, 

respectively. The mean concentrations of Zn, Mo and U at 0.64, 0.83 and 0.78 fig/1, respectively, 

are slightly elevated compared to other rock types in this study, probably due to the presence of 

weakly mineralized rocks in some of the watersheds. The mean concentrations of Al, Fe, and 

Mn are low at 14, 13, and 0.3 fig/1, respectively. Alkalinity values range from 20 to 50 mg/1 as 

HCO3" with a mean of 34 mg/1. The low mean alkalinity value indicates that the rocks have low 

capacity to neutralize introduced acidity. The chemical quality of the waters evolving within 

these rocks is excellent.

40
- 38° 37'30"

1 Mile

Figure 15. Site locations for stream waters from areas underlain by Tertiary

and Proterozoic intrusive rocks and Proterozoic metamorphic rocks 

in the Quartz Creek area, Gunnison national Forest.

41
106°22f 30n

Gunnlson National Forest

38° 30f

 Stream site 

o Spring site

21

0 1 mile

Figure 16. Site locations for stream and spring waters from areas underlain by 

Proterozoic intrusive rocks and Proterozoic metamorphic rocks along 

the western flank of the Sawatch Range, Gunnison National Forest.

42
Table 13. Eight waters from Tertiary and Proterozoic granite and quartz monzonite and Proterozoic 

feisic and hornblende gneiss.

Measurement1

Conductivity 

PH 

Ca

Mg 

Na

K

SiO2

Alkalinity 

SO4

Cl

F

Al

Fe

Mn

Cu

Zn

Pb

Mo

Sb

As

Th

U

Li

Ba

Sr

V

Sc

Rb

Y

Zr

La

Br

I

Range

Minimum

47 

6.89 

5.8

0.51 

1.2

0.24

6.1

20 

1

<0.25

<0.1

5.1

<5

<0.3

<1

0.22

<0.1

<0.5

<0.01

<0.03

0.023

0.17

0.68

2.6

28

<0.5

<10

0.12

<0.3

0.084

<0.005

<3

<0.2

Maximum

126 

8.18 

12

4.1 

5.3

0.84

22

50 

15

0.9

2.2

47

35

0.49

1

5.1

1.3

2.9

0.15

<0.03

0.37

7.3

5.7

29

48

0.57

30

1.5

0.77

12.5

0.57

<3

3.2

Mean2

83 

7.82 

8

1.7 

3.1

0.55

14

34 

3.5

0.39

0.21

14

13

<0.3

<1

0.64

0.2

0.83

0.015

<0.03

0.077

0.78

1.7

8.7

37

<0.5

20

0.35

0.17

0.35

0.036

<3

0.22

, Mg, Na, K, SiO2, SCU, Cl, and F in mg/l, alkalinity in mg/l HCOs, 

conductivity in uS/cm, remaining elements in ug/l 

2AII variables are geometric means except for pH which is arithmatic mean.

43
Comparison of Water Chemistry from each of the Ten Rock Types

The chemistry of water evolving in the mountainous headwater areas depend on the 

chemical composition of the underlying rock type. A unique range of water chemistry evolves 

within each rock type For the ten rock compositional types in this study, the means of selected 

species and other parameters are shown in Table 14. A discussion follows concerning rock 

compositional types and selected variables and species.

Total dissolved solids (TDS) values can be used to compute rock weathering rates at 

which rivers transport chemical weathering products to the ocean. The TDS values can be used 

to compare waters from different geologic terrains as a means of comparing chemical weathering 

rates. TDS values are calculated by recalculating the bicarbonate ion in terms of carbonate in the 

solid phase and summing the remaining chemical data. The bicarbonate ion is converted to 

carbonate in the solid phase because the bicarbonate ions were derived from the atmosphere 

rather than rocks (Hem, 1992). Mean TDS values for waters from the ten rock types are shown 

in Table 14. Waters with the highest mean TDS values evolve from areas underlain by Mesozoic 

sedimentary rocks followed by Tertiary sedimentary rocks. Dissolved solids in the waters 

depend on the rock compositional type, but also time of contact of the waters and rocks and 

evaporation effects. One way to minimize the time of contact and evaporation effects is by 

normalizing TDS values by dividing by the Cl content for each site. This assumes that Cl 

content is conservative and there is no addition of Cl to the waters by the dissolution of minerals 

containing Cl (such as halite). Table 15 shows the results of normalizing the TDS values. The 

waters with the highest normalized TDS values are from areas underlain by Paleozoic 

sedimentary rocks followed by the Mancos Shale, Tertiary sedimentary rocks, and the Mesaverde 

Formation. The waters with the lowest normalized TDS values are from areas underlain by 

Mesozoic sedimentary rocks and Tertiary ash-flow tuff. The Paleozoic sedimentary rocks are 

undergoing the most rapid potential rate of chemical weathering, supplying the most dissolved 

solids to the waters of the area. Potential release of TDS is used to indicate that chemical 

weathering and the release of TDS is dependent on amounts of precipitation. Variation in 

amounts of precipitation will affect the rate of chemical weathering. Potential release of TDS 

does not take into account the amount of precipitation of an area. The probable presence of 

gypsum in the Paleozoic sedimentary rocks is a major contributor to the TDS of waters evolving 

in rocks underlain by these rocks. The Mesozoic sedimentary rocks and the Tertiary ash-flow 

tuff are undergoing the lowest potential rate of chemical weathering and supplying the lowest 

amounts of dissolved solids to the waters of the area. The Mesozoic sedimentary rocks contain 

abundant well crystallized silica minerals that are resistance to weathering. The Tertiary ash44
Table 14. Summary of chemical composition of waters from various rock types, Grand Mesa, Uncom

and Gunnison National Forests, Colorado

Dominant Rock Compositonal Type Setting Relief Precipitati

annual, inc

Tertiary basalt flows and associated rocks 

Tertiary felsic ash-flow tuff 

Tertiary quartz latitic lava and breccia 

Tertiary andesitic lava, breccia, tuff 

Tertiary sedimentary rocks 

Cretaceous Mesaverde Formation 

Cretaceous Mancos Shale 

Mesozoic sedimentary rocks 

Paleozoic sedimentary rocks

Tertiary and Proterozoic felsic and intermediate 

intrusive and Proterozoic metamorphic rocks

Grand Mesa low 30 to 45

San Juan volcanic field high 16 to 30

San Juan volcanic field high 16 to 25

West Elk volcanic field high 20 to 40

Battlement and Grand Mesa moderate 20 to 35

Piceance basin and high 20 to 35

Elk Mountains

San Juan volcanic field high 16 to 40 

and Paradox basin 

Uncompahgre uplift high 16 to 25

west flank Sawatch Range high 25 to 40 

Sawatch Range high 16 to 35
ON

Number

4

5

4

8

7

8

10

5

15

8

Dominate water

type

Ca, HCO3

Ca, HCO3

Ca, HCO3

Ca, HCO3

Ca, HCO3

Ca, HCO3

Ca, HCO3

Ca, HCO3

Ca, HCO3

Ca, HCO3

IDS

39.3

74.5

93

109

196

69.5

134

200

174

50.9

pH

7.41

7.43

7.48

7.99

8.50

8.31

8.20

7.94

8.30

7.82

Conductivity

uS/cm

63

100

124

158

365

126

258

413

356

83

Ca

ppm

5.4

11

12.6

16

39

13

32

59

52.6

8

Mg

Ppm

2.1

1.7

1.8

3

12

3

7.5

10

11.0

1.7

Na

ppm

1.8

4.4

6.9

7.7

15

5.4

4.7

5.2

1.3

3.1

K

ppm

0.37

1.3

1.1

1.7

1.4

0.49

0.36

1.8

0.47

0.55

SiO2

14

29

30.8

35

18

13

14

11

6.3

14

Alkalinity

ppm

28

46

36

72

191

54

101

205

143

34
Fe

ppb

91

65

60

16

13

14

15

<5

<20

13

Mn Cu

PPb ppb

15 <1

2.9 <1

2.7 0.56

0.48 <1

4.7 <1

2.0 <1

2.2 <1

0.68 <1

0.57 O.5

<0.3 <1

Zn

ppb

0.40

0.24

0.5

0.22

0.22

0.24

0.21

0.23

0.6

0.64

Co

PPb

0.5

O.5

0.06

0.5

O.5

0.5

0.5

O.5

0.06

0.5

Mo

ppb

O.5

0.5

0.41

O.5

1.9

O.5

0.71

0.5

0.41

0.83

Ni

ppb

<2

<2

0.4

<2

<2

<2

<2

<2

1.2

<2

Cr

ppb

O.1

O.1

<1

O.1

O.1

O.1

O.1

O.1

2.6

O.1

As

ppb

0.048

1.2

<3

0.7

1.9

0.08

0.12

1.2

<3

O.03

Sb

ppb

0.017

0.021

0.1

0.012

0.12

O.010

0.015

0.019

O.1

0.015

W

PPb

0.20

O.01

O.02

O.01

0.018

0.01

O.01

O.01

0.02

0.03

Pb

ppb

0.15

0.12

O.05

0.10

0.18

O.10

O.10

0.13

0.05

0.2

P

0.

0.

0.

0.

1

0

0

2

0

0
00

Ba

ppb

14

18

4.6

5

62

18

18

286

88.5

8.7

Ti

ppb

2.1

<2

1.8

<2

<2

<2

<2

<2

0.3

<2

Sc

ppb

21

35

2.9

41

25

18

19

15

0.9

20

V

ppb

<0.5

1.2

1.1

2.2

2.8

<0.5

0.43

0.68

0.9

<0.5

Se

ppb

<0.2

<0.2

<5

<0.2

<0.2

<0.2

<0.2

0.27

<5

<0.2

Br

ppb

<3

3.5

n.d.

<3

6.6

<3

<3

8

n.d.

<3

I

ppb

0.98

2.2

n.d.

0.21

1.5

<0.2

0.51

0.98

n.d.

0.22

Sr

ppb

36

79

115

95

311

102

169

241

107

37

Rb

ppb

0.50

1.2

1.4

2.4

0.60

0.32

0.16

2.4

0.47

0.35

Y

ppb

0.41

0.10

0.32

0.071

0.083

0.042

0.053

0.035

0.03

0.17

Zr

ppb

0.43

0.51

0.3

0.28

0.42

0.15

0.067

0.14

<0.05

0.35
Table 15. Normalized values for selected parameters and species of waters from watersheds within G

Tertiary basalt flows and associated rocks

Tertiary felsic ash-flow tuff

Tertiary quartz latitic lava and breccia

Tertiary andesitic lava, breccia, tuff

Tertiary sedimentary rocks

Cretaceous Mesaverde Formation

Cretaceous Mancos Shale

Mesozoic sedimentary rocks

Paleozoic sedimentary rocks

Tertiary and Proterozoic intrusive and metamorphic rocks

Chloride

0.29

0.88

0.56

0.65

1.4

0.49

0.8

3.4

<0.25

0.39

TDS

39.3

74.5

93

109.4

196

69.5

133.8

200.3

174

50.9

TDS/CI

133.8

84.7

166

155.5

144.6

141.5

222.2

58.1

714.6

131.5

Total dissolved solids(TDS) in mg/l, chloride, sulfate, and fluoride in mg/l, alkalinity in mg/l HCOa, rem
Sulfate

0.65

2.7

16.6

3.5

8.1

5.3

18

4.7

13.5

3.5

Sulfate/CI

2.24

3.07

305

5.79

10.82

30

1.34

54

8.97

F

0.07

0.1

<0.1

0.07

0.16

0.11

0.12

0.12

<0.1

0.21

F/CI

0.24

0.11

0.125

0.1

0.11

0.22

0.2

0.03

0.28

0.54

U1

0.069

0.058

0.14

0.092

1.4

0.13

0.27

2.7

0.56

0.78

U/CI

0.24

0.07

0.25

0.131

0.27

0.45

0.77 , 2.24

2 ,

Li

0.3

1.5

3.6

1.3

7.2

1.4

1.6

12

2.1

1.7

Li/CI

1.03

1.7

6.4

1.86

5.14

2.86

2.67

3.43

8.4

4.36
flow tuff is felsic in composition and more resistance to weathering than more mafic rocks.

Spacial maps are constructed showing the potential release of TDS by recalculating the 

normalized TDS values. The highest mean normalized TDS value is from Paleozoic sedimentary 

rocks and is assumed to be one. The recalculated mean normalized TDS values for the remaining 

rock compositional types are calculated by dividing by the highest mean normalized TDS value. 

Rankings of potential release of TDS are shown in Table 16. Maps showing potential release of 

TDS are made for each of the three National Forests by plotting the recalculated mean 

normalized TDS values from Table 16 by rock compositional types. The maps of potential 

release of TDS for the three National Forests are shown in figs. 17-19.

Mean values for pH of waters from areas underlain by the ten rock compositional types 

range from 7.41 for Tertiary basaltic rocks to 8.50 for Tertiary sedimentary rocks. The pH values 

in these headwater streams are affected by the amount of melting snow runoff as a component of 

the total flow and the time of contact of water and rock. The snow runoff will generally lower 

the pH, and the time of contact of water and rock will generally increase the pH value. In 

addition, high biotic activity in the soil zone may release organic acids and may lower pH. 

Because pH of the waters are important for assessments of acidity of the watersheds, spacial 

maps were made of mean pH by plotting the mean pH values for each of the rock compositional 

types for each of the three National Forests (figs. 20-22).

Alkalinity of a solution is the capacity for solutes it contains to react with and neutralize 

acid (Hern, 1992). The property of alkalinity is determined by titration with a strong acid. 

Several different solute species may contribute to alkalinity, but for almost all natural fresh 

waters, the alkalinity is produced by the dissolved carbon dioxide species, bicarbonate and 

carbonate (Hem, 1992). Alkalinity in this study is reported as equivalent amounts of 

bicarbonate. Therefore in this study, alkalinity is the capacity of the water to react and consume 

acid. If an area is affected by acid mine drainage or acid rain, the alkalinity will consume the 

introduced acid until all the alkalinity is consumed. After this, if acidity is still being introduced, 

the acidity of the water will increase. So the alkalinity is a measure of the capacity of a 

watershed to resist the introduction of acidity. The higher the alkalinity value, the greater the 

capacity of the water to consume acid. The mean alkalinity values of waters from areas 

underlain by the ten rock types range from 28 to 205 mg/1 as HC03". The waters with the highest 

alkalinity values are from areas underlain by Mesozoic sedimentary rocks. The waters with the 

lowest alkalinity values are from areas underlain by Tertiary basaltic rocks (Table 14). 

Alkalinity in the waters depends on the rock compositional type, but also time of contact of the 

rocks and water and evaporation effects. To decrease the effect of time of contact and 

evaporation effects, alkalinity is normalized using the Cl content in a manner similar to that done 

when normalizing TDS. This assumes that Cl content is conservative and there is no addition of

51
Table 16. Rankings of rock composition type as to potential release of TDS and acid neutralizin

acidity in the GMUG area

K>

Potential release of TDS

Rock Composition

Tertiary basalts

Tertiary felsic ash flow tuff

Tertiary latitic lava and breccia

Tertiary andisites

Tertiary Sedimentary rock

Mesaverde Formation

Mancos Shale

Mesozoic Sedimentary rock

Paleozoic Sedimentary rock

Tertiary and Proterozoic intrusive rocks

TDS

39.3

74.5

93

109.4

196

69.5

133.8

200.3

174

50.9

TDS/CI

133.8

84.7

166

155.5

144.6

141.5

222.2

58.1

714.6

131.5

Rock Composition

Tertiary basalts

Tertiary felsic ash flow tuff

Tertiary latitic lava and breccia

Tertiary andisites

Tertiary Sedimentary rock

Mesaverde Formation

Mancos Shale

Mesozoic Sedimentary rock

Paleozoic^ Sedimentary rock

Tertiary and Proterozoic intrusive rocks

Acid-Neutralizing

Alkalinity as mg/l HCO3

28

46

36

72

191

54

101

205

143

34

Capacity

Normalized Alk (Alk/CI)

97

52

64

103

136

110

168

59

572

87

Recalcula
39°

Moderately potential release of TDS (0.31)

Moderately low potential release of TDS (0.19-0.20))

0 10 Miles

Figure 17. Potential release of total dissolved solids (TDS) in stream and spring waters, 

Grand Mesa National Forest.

53
I

108°

Delta

Montrose

38

Area impacted by 

significant mining

High Potential for TDS (0.3) 

Moderate Potential for TDS (0.15-0.18) 

Low Potential for TDS (0.08) 

Not Determined

10 Miles

Figure 18. Potential for high total dissolved solids (TDS) in stream and spring waters, 

Uncomphagre National Forest, Colorado.

54
- 39°

10 Miles

Very High Potential for TDS (1.0)

Moderately High Potential for TDS (0.3)

Moderate Potential for TDS (0.15-0.18)

Low Potential for TDS (0.08)

Figure 19. Potential for total dissolved solids (TDS) in stream and spring waters, 

Gunnison National Forest, Colorado.

55
39°

Sightly Alkaline Mean pH value (7.41) 

Moderately Alkaline Mean pH value (8.24-8.3) 

Alkaline Mean pH value (8.50)

0 10 Miles

Figure 20. Mean pH values of stream and spring waters, Grand Mesa National Forest.

56
108°

. Delta f

Montrose

- 38

Area impacted by 

significant mining

n

Slightly Alkaline Mean pH (7.41-7.48) 

Moderate Alkaline Mean pH (7.82-7.99) 

Moderately High Alkaline Mean pH (8.20-8.31) 

Not Evaluated

10 Miles

Figure 21. Mean pH values of stream and spring waters, Uncomphagre National Forest.

57
10 Miles

Slightly Alkaline pH (7.41-7.48)

Moderately Low Alkaline pH (7.82-7.99)

Moderate Alkaline pH (8.20-8.31)

Alkaline pH (8.50)

Figure 22. Mean pH values for stream and spring waters, Gunnison National Forest.

58
39C

Moderately high acid-neutralizing capacity (0.29) 

Moderate acid-neutralizing capacity (0.24)

Moderately low acid-neutralizing capacity (0.17-0.19)

0 10 Miles

Figure 23. Acid-Neutralizing capacity to introduced acidity, Grand Mesa National Forest

59
108°

38

'Area impacted by 

significant mining

| Moderately High Acid-Neutralizing Capacity (0.24-0.29) 

 Moderately Low Acid-Neutralizing Capacity (0.15-0.19)

D Low Acid-Neutralizing Capacity (0.0.09-0.11)

0 

CH Not Determined

10 Miles

Figure 24. Acid-neutralizing capacity to introduced acidity, Uncomphagre National 

National Forest.

60
39°

High Acid-Neutralizing Capacity (1.0)

Moderately High Acid-Neutralizing Capacity (0.24-0.29)

Moderate Acid-Neutralizing Capacity (0.15-19) 

Low Acid-Neutralizing Capacity (0.09-0.11)

10 Miles

Figure 25. Acid-neutralizing capacity to introduced acidity, Gunnison National Forest.

61
dissolved solids to the waters by the dissolution of soluble salts containing Cl. The waters with 

the highest mean normalized alkalinity value are from areas underlain by Paleozoic sedimentary 

rocks, followed by the Mancos Shale and Tertiary sedimentary rocks (Table 15). The waters 

with the lowest mean normalized alkalinity values are from areas underlain by ash flow tuff. The 

normalized alkalinity value is a measure of the susceptibility of the watershed to resist introduced 

acidity.

Spacial maps are constructed showing acid-neutralizing capacity by recalculating the 

mean normalized alkalinity values. The highest mean normalized alkalinity value is from 

Paleozoic sedimentary rocks and is assumed to be one. The recalculated mean normalized 

alkalinity values for the remaining rock compositional types are calculated by dividing by the 

highest mean normalized alkalinity value. Rankings of acid-neutralizing capacities are shown in 

Table 16. Maps showing acid-neutralizing capacities are made for each of the three National 

Forests by plotting the recalculated mean normalized alkalinity values from Table 16 by rock 

compositional types. The maps of the three National Forests are shown in figs. 23-25.

Mean concentrations of silica in waters from areas underlain by the ten compositional 

rock types range from 11 mg/1 for Mesozoic sedimentary rocks to 35 mg/1 for Tertiary andesitic 

rocks (Table 14). Other high mean silica concentrations in waters are from areas underlain by 

Tertiary quartz latitic lava and breccia (31 mg/1) and ash flow tuff (29 mg/1). The high mean 

silica values are probably because these rocks contain fine-grained silicate minerals with high 

surface areas, particularly susceptible to the dissolution of silica. Conversely, the Mesozoic 

sedimentary rocks contain sandstone composed of larger sized and well crystallized mineral 

grains that have less surface areas. These grains are more resistant to silica dissolution.

Mean concentrations of waters from watersheds underlain by the ten rock types are all 

low in Cu, Zn, Co, Ni, Cr, Sb, Pb, and Be (Table 14). In addition, the mean values for Se are all 

< 0.2 ng/1 except for waters from areas underlain by Mesozoic sedimentary rocks, for which the 

mean is 0.27 ng/1. Thus the contribution of Se in these mountainous headwater watersheds is 

very low. The Mancos Shale is known to be a source for Se concentrations in water, in the lower 

valleys, particularly in areas of irrigation (Wright and Butler, 1993). In these mountainous 

headwater streams in areas underlain by the Mancos Shale, evaporation effects are minimal and 

Se concentrations in waters are low.

Mean concentrations for Mo are low, except for a slightly elevated mean value in waters 

from areas underlain by Tertiary sedimentary rocks (1.9 Hg/1). Mean concentrations for U are 

low, except for slightly elevated mean values in waters from areas underlain by Mesozoic 

sedimentary rocks (2.7 ng/1) and Tertiary sedimentary rocks (1.4 fig/1). Mean concentrations of 

As are low for waters from the three National Forests, except for waters from areas underlain by 

Tertiary sedimentary rocks (1.9 fig/1), Tertiary ash-flow tuff (1.2 Hg/1), and Mesozoic

62
sedimentary rocks (1.2 ^ig/1), all with slightly elevated mean values (Table 14).

Mean values for Al, Fe, and Mn are all low in waters from watersheds underlain by the 

ten rock compositional types except for elevated mean values for Al, Fe, and Mn in waters from 

areas underlain by Tertiary basaltic rocks ( 54, 91, and 15 jig/1, respectively), elevated Al and Fe 

from areas underlain by Tertiary quartz latitic lava and breccia (55 and 60 jig/1, and elevated 

mean Fe in waters from areas underlain by Tertiary ash flow tuff (65 \ig/\) (Table 14).

Sulfate, F, and U and are mobile as anionic species in alkaline waters. These elements 

will concentrate in waters, depending on the time of contact of water and rock and evaporation 

effects. The highest mean sulfate concentration is in waters from areas underlain by the 

Mesaverde Formation at 18 mg/1 (Table 14). The Mesaverde Formation contains coal with 

associated pyrite. The weathering of the pyrite is probably the source of the sulfate. To reduce 

the effects of evaporation and time of contact of water and rock, sulfate values are normalized by 

dividing by the Cl concentrations for each water sample and the means calculated. The highest 

mean normalized values for sulfate are waters from areas underlain by Paleozoic sedimentary 

rocks and the Mancos Shale followed by the Tertiary sedimentary rocks and the Mesaverde 

Formation (Table 15). The highest mean normalized sulfate value in waters from Paleozoic 

sedimentary rocks is probably due to the presence and dissolution of gypsum in the rocks. The 

high values in waters from the other rock compositional types are probably due to the weathering 

of pyrite, present in the sedimentary rocks.

The highest mean F concentration of 0.21 mg/1 is in water from areas underlain by 

Tertiary intrusive and Proterozoic rocks (Table 14). The high concentrations of F in waters is 

probably because of the high F content of the Tertiary and Proterozoic intrusive rocks. When F 

is normalized in a manner similar to sulfate, these rocks are even more anomalous compared to 

the other major rock compositional types (Table 15). Interestingly, the Tertiary basaltic rocks are 

next highest in normalized F, which suggest that the basaltic rocks are elevated in F.

The highest mean U concentrations (Table 14) are in waters from areas underlain by 

Mesozoic sedimentary rocks ( 2.7 jig/1), Tertiary sedimentary rocks (1.4 ^ig/1), and Tertiary 

intrusives and Proterozic rocks ( 0.78 |ig/l). When U is normalized, similar to sulfate, the highest 

values (Table 15) are in waters from areas underlain by Tertiary intrusive and Proterozoic rocks 

(2.00), Tertiary sedimentary rocks (1.00), and Mesozoic sedimentary rocks (0.77). These higher 

values suggest that these rock compositional types contain elevated concentrations of leachable 

U.

The highest mean Li values are in waters from areas underlain by Mesozoic sedimentary 

rocks with a mean of 12 |ig/l, which is high compared to the remaining rock compositional types 

(Table 14). Much of the high mean Li concentration is due to the longer time of contact of water 

and rock and the evaporation effects of these mostly spring waters. If Li is normalized in a

63
similar manner to that above, the waters with the highest mean normalized Li values are from 

Tertiary sedimentary rocks (5.14), followed by Tertiary intrusive and Proterozoic rocks (4.36), 

and Mesozoic sedimentary rocks (3.43) (Table 15).

When normalized so the effects of evaporation and time of contact of water and rock are 

minimized, the waters from watersheds underlain by Tertiary intrusive rocks and Proterozoic 

rocks are high in mean normalized F, U, and Li, compared to other rock compositional types in 

three National Forests. This suggests that these rocks are elevated in these elements, as would be 

expected for evolved felsic rocks.

To gain understanding of processes such as speciation of elements and identification of 

minerals that may control the concentration, mobility, and attenuation of elements in the stream 

waters, chemical modeling of the stream waters was carried out using PHREEQC (Parkhurst, 

1995). The modeling program assumes mineral-solution equilibrium. For some chemical 

reactions, particularly with slow kinetics, this may not be the case. Except for Al, the cations in 

the stream waters occur mostly as simple cations and the anions as chloride, sulfate, carbonate, 

and bicarbonate complexes (Table 17). In addition, the state of saturation of the waters with 

mineral phases were calculated. Saturation indexes were calculated for a suite of minerals to 

determine if concentrations of trace metals in water were controlled by mineral phases. The 

saturation index is a convenient means of expressing saturation states of minerals (Barnes and 

Clark, 1969 where:

SI=log, 0 IAP/KT.

In the expression, SI is the saturation index, IAP is the ion activity product, and KT is the 

equilibrium constant of the dissolution reaction at the temperature of the sample. Mineral phases 

are supersaturated at SI>0, saturated at SI=0, and undersaturated at SI<0.

The input for the modeling was the mean values for each rock compositional type shown 

in Table 14. The waters from areas underlain by Tertiary sedimentary rocks, the Mancos Shale, 

Mesozoic sedimentary rocks, and Paleozoic sedimentary rocks are supersaturated with respect to 

calcite and dolomite (Table 18). These are headwater streams and not streams in the valleys 

where secondary calcite is abundant. Therefore the waters are in contact with dissolving 

carbonate minerals, such as calcite and dolomite present in these rock units. Another mineral 

which has an influence on the control of species in water is chalcedony. Most of the waters from 

all the rock compositional types are saturated or slightly oversaturated with respect to chalcedony 

(Table 18), which appears to control the amount of dissolved silica in the waters. Waters from 

Tertiary sedimentary rocks are oversaturated with respect to sepiolite (Table 18), which appears 

to control Mg mobility and may reflect the weathering of dolomite as the source for Mg.

64
Table 17. Speciation of selected elements in waters from GMUG.

Element Specie

Ca Ca2+

Mg Mg2+

Na Na+

K K+

S SO42'

C HCO3-

Cl ClF FSi H4SiO40

Al AI(OH)4-

Fe Fe2+ 

Mn _________Mn2+ , except Tertiary sediments as MnCOs0

65
Table 18. Saturation indices for selected minerals for waters from GMUG.

Rock composition type

Tertiary basalt flows

Tertiary felsic ash-flow tuff

Tertiary quartz latitic lava, etc

Tertiary andesitic lava, etc.

Tertiary sedimentary rocks

Cretaceous Mesaverde Fm

Cretaceous Mancos Shale

Mesozoic sedimentary rocks

Paleozoic sedimentary rocks

Tertiary and Proterozoic intrusive

and metamorphic rocks

Calcite

-1.92

-1.42

-1.49

-0.57

0.78

-0.36

0.23

0.35

0.51

-1.34

Dolomite

-4.09

-3.54

-3.76

-1.73

1.28

-1.15

0.04

0.02

0.45

-3.28

Siderite

-1.47

-1.45

-1.6

-1.42

-0.69

-1.16

-0.95

-1.67

-0.89

-1.93

Rhodochrosite

-1.97

-2.51

-2.66

-2.65

-1.08

-1.8

-1.53

-2.27

-2.18

-3.46

Chalcedony

0.08

0.43

0.48

0.45

0.11

0

0.04

0.01

-0.24

0.14

Gypsum

-4.57

-3.68

-2.84

-3.38

-2.85

-3.34

-2.37

-2.89

-2.47

-3.68

Flu

-4

-3

-3

-3

-2

-3

-2

-2

-3

-2

Bold type indicates satuartion or supersaturation of the waters with respect to mineral phase

Os 

Os
Comparison of the Waters from the Ten Rock Compositional 

Types with Mineralized Rocks

No significant mineralization or mining has taken place in the watersheds sampled in the 

three National Forests. Significant mineralization has taken place in other watersheds in the 

three National Forests, particularly the upper Uncompahgre and San Miguel Rivers and around 

the Crested Butte area. These areas have been affected by the mining and the determination of 

natural baselines for these areas can not be done directly. Contamination from mining has 

altered the natural background of waters in watersheds where mining has taken place. Redcloud 

Peak area near Lake City is administered by the Bureau of Land Management (BLM) and is 

adjacent to the Gunnison and Uncompahgre National Forests. The area contains significant 

mineralization, but no significant mining has taken place. Water samples of streams from the 

Redcloud Peak area were collected in a prior study (Miller and McHugh, 1998). The water 

chemistry of this mineralized area can be compared to the waters from the ten rock compositional 

types in the GMUG area in order to evaluate the effects of significant mineralization on water 

chemistry. The waters from the Redcloud Peak area approximate, in a qualitative manner only, 

the natural baselines of waters from watersheds within the mined areas in the GMUG areas. This 

comparison is only to show trends of what the effect of mineralization is on water chemistry in 

watersheds containing significantly mineralized rocks, and not to determine the pre-mining 

natural geochemical baselines of waters from mined watersheds in the GMUG area. The 

Redcloud Peak area is located within the Lake City caldera. Samples of water were collected in 

July, 1994 from 19 headwater streams in watersheds underlain by the Sunshine Peak silicic 

alkalic rhyolite tuff. The tuff unit is a multiple-flow more than 1 km thick, densely welded and 

propylitically altered about 22.5 m.y. ago (Lipman, 1976). The chemical analyses of the 19 

stream waters are shown in the appendix 2. A summary of the ranges and means of selected 

species in stream waters from the Redcloud Peak area is shown in Table 19.

The relief of the Redcloud Peak area is high and the dominant vegetation is alpine tundra 

and subalpine forest. Annual precipitation ranges from 25 to 40 inches. The 19 sites are mostly 

Ca2+-SO42" type waters, which is in contrast to the GMUG waters which are mostly Ca2+- HGO3 " 

type waters. The waters are acidic to slightly alkaline in pH with moderately low conductivity 

values. Natural acid-drainage waters are present in the upper portions of several of the 

watersheds. Abundant Al hydroxides precipitate along several streams and at junctions with 

tributaries. Fe hydroxides are also precipitating, but are not as abundant as the Al hydroxides. 

The mineralized rocks contain disseminated pyrite and the oxidation and dissolution of the pyrite 

release acidity and sulfate to the waters (see Miller and others (1998) for details on these

67
Table 19. Nineteen waters from areas underlain by the mineralized Sunshine Peak rhyolitic ash-flow tuff, 

Lake City caldera.

Measurement1

Conductivity

IDS

pH

Ca

Mg

Na

K

SiO2

Alkalinity

SO4

Cl

F

Al

Fe

Mn

Cu

Zn

Mo

As

U

Li

Ba

Sr

Sc

Rb

Y

La

Range

Minimum

44

31.3

3.58

6.3

0.5

0.4

0.3

3

<1

6.9

<0.1

<0.5

<100

<10

<10

<1

<5

<1

<1

<0.1

<1

0.9

29

2

0.8.

<0.1

<0.1

Maximum

320

166.7

7.6

33

4.5

4.4

4.5

29

94

106

0.18

0.96

4400

450

2000

6

280

9

1

8.1

21

32

320

8.9

21

13

66

Mean2

110

66.4

6.09

12

1.6

1

1

8.4

3.9

30

0.12

0.17

420

30

40

1.2

11

1

<1

0.66

3.7

7.7

72

5.1

3.3

0.43

0.58

n TDS, Ca, Mg, Na, K,

in mg/l HCOa, conductivity

2AII variables are geometric

SO4, Cl, and F in mg/l, alkalinity

in uS/cm, remaining elements in ug/l.

means except for pH

68
processes for natural acid drainage in this area). Al is mobilized because of the low pH values. 

Values for pH range from 3.58 to 7.6 with a mean of 6.09 (Table 19). The mean pH value of 

waters from areas underlain by the mineralized Sunshine Peak Tuff is much lower than waters 

from areas underlain by the ten predominantly unmineralized rock types from the GMUG area 

(Table 20). Because of the low pH values, most of the alkalinity generated in the Rede loud Peak 

area is consumed by the acidity released by the weathering of pyrite. Alkalinity values range 

from 0 to 94 mg/1 as HCO3", with a mean of 3.9 mg/1. This is much lower than mean alkalinity 

values of waters from the GMUG area. If mean alkalinity values are normalized in a manner 

similar to that done for the waters from the GMUG area, the mean normalized alkalinity is also 

much lower than waters from the GMUG area (Table 21).

Values for conductivity for waters from the Redcloud Peak area range from 44 to 320 

p,S/cm, with a mean of 110 p,S/cm, which is moderately low and a reflection of the large input of 

runoff from melting snow, the short time of contact of waters with rocks, and the poor 

groundwater reservoir of this mountainous headwater area. Concentrations of Cl are very low 

with a mean of 0.12 mg/1, again suggesting a large input of runoff from melting snow. Mean 

TDS values of waters from the Sunshine Peak is 66.4 mg/1 (Table 20), which is lower than 8 of 

the rock compositional types from the GMUG area. If TDS is normalized in a manner similar to 

that done for the waters from the GMUG area, the mean normalized TDS is second only to 

waters from areas underlain by Paleozoic sedimentary rocks (552 vs. 715) (Table 21). Therefore 

the potential release of TDS from areas underlain by the mineralized Sunshine Tuff is higher 

than nine of the ten areas of predominantly unmineralized rocks in the sampled watersheds in the 

GMUG area.

Sulfate concentrations in waters from areas underlain by the Sunshine Peak Tuff range 

from 6.9 to 106 mg/1 with a mean of 30 mg/1 (Table 19). This mean value is much higher than 

the means of waters from the sampled GMUG watersheds, mainly because larger amounts of 

pyrite, which is the likely source of the sulfate, are present in the Sunshine Peak Tuff than 

sampled watersheds in the GMUG area. If the sulfate concentrations are normalized by dividing 

by Cl concentrations to reduce the effect of time of contact of water and rock and evaporation, 

the differences are even more striking (Table 21).

Mean value of F of waters from areas underlain by the Sunshine Peak Tuff is 0.17 mg/1 

(Table 19). Only waters from areas underlain by Tertiary intrusive and Proterozoic rocks in the 

GMUG areas have a higher mean F concentration of 0.21 mg/1. If the F concentration is 

normalized by dividing by the Cl concentration, the mean value of waters from areas underlain 

by the Sunshine Peak Tuff area is 1.41 compared to 0.54 from the Tertiary intrusive and 

Proterozoic rocks areas (Table 21). This suggests that the F content in the Sunshine Peak Tuff is 

higher than rocks in the GMUG study areas, including the Tertiary intrusive and Proterozoic

69
Table 20. Comparison of the geochemistry of waters from watersheds underlain by relatively unmin

areas to wates from mineralized Sunshine Peak tuff, Redcloud Peak area.

Rock composition type Number

GMUG area

Tertiary basalt flows and associated rocks

Tertiary felsic ash-flow tuff

Tertiary quartz latitic lava and breccia

Tertiary andesitic lava, breccia, tuff

Tertiary sedimentary rocks

Cretaceous Mesaverde Formation

Cretaceous Mancos Shale

Mesozoic sedimentary rocks

Paleozoic sedimentary rocks

Tertiary and Proterozoic intrusive and meta

4

5

4

9

7

8

11

5

15

8

Water Type

Ca, HCOs

Ca, HCOs

Ca, HCOs

Ca, HCOs

Ca, HCO3

Ca, HCO3

Ca, HCO3

Ca, HCOs

Ca, HCOs

Ca, HCOs

Temp 

°C

12.2

9.9

7.0

12.6

15.9

14.4

14.4

8.8

9.4

7.3

pH Condu

uS

7.41

7.43

7.48

7.94

8.50

8.31

8.24

7.94

8.30

7.82

6

1

1

15

3

1

29

4

35

8

Redcloud Peak Area

Sunshine Peak Tuff 19 Ca, SO4 9.7 6.09 1
Mg 

mg/l

2.1

1.7

1.8

2.8

12.0

3

8.6

10

11.0

1.7

Na 

mg/l

1.8

4.3

6.9

7.3

15

5.4

6.1

5.2

1.3

3.1

K

mg/l

0.37

1.3

1.1

1.6

1.4

0.49

0.45

1.8

0.47

0.55

SiO2 

mg/l

14.3

29.9

30.8

34.2

17.5

12.8

13.9

10.9

6.3

14.3

Alkalinity 

mg/l

28

46

36

67

191

54

104

205

143

34

SO4 

mg/l

0.65

2.7

16.6

4.1

8

5.3

24

4.7

13.5

3.5

Cl 

mg/l

0.29

0.88

0.56

0.65

1.4

0.49

0.80

3.4

<0.25

0.39

F 

mg/l

O.10

0.10

O.10

O.10

0.16

O.10

0.12

0.12

<0.1

0.21

Al 

ug/l

54

16

55

13

12

12

10

6.7

0.34

14

Fe 

ug/l

91

65

60

15

13

14

17

4.6

<20

13

1.6 1 1 8.4 3.9 30 0.12 0.17 420 30 
to

Co 

ug/l

<0.5

<0.5

0.06

<0.5

<0.5

<0.5

<0.5

<0.5

0.06

<0.5

Mo 

ug/l

<0.5

<0.5

0.41

<0.5

1.9

<0.5

0.77

<0.5

0.41

0.83

Ni 

ug/l

<2

<2

0.4

<2

<2

<2

<2

<2

1.2

<2

Cr As 

ug/l ug/l

<0.1 0.05

<0.1 1.2

<1 <3

<0.1 0.47

<0.1 1.9

<0.1 0.08

<0.1 0.16

<0.1 1.2

2.6 <3

<0.1 <0.03

U 

ug/l

0.07

0.06

0.14

0.08

1.4

0.14

0.35

2.7

0.56

0.78

Li 

ug/l

<0.5

1.5

3.6

1.2

7.2

1.4

2.0

12

2.1

1.7

Be 

ug/l

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

Ba 

ug/l

14

18

4.6

4.6

62

18

19

286

88.5

8.6

Sc 

ug/l

21

34

2.9

39

25

18

20

15

0.9

19

1.1 1.1 <0.2 <1 0.66 3.7 0.48 7.7 5.1 
Table 21. Normalized values for selected parameters and species of waters from relatively un

within GMUG compared to waters from watersheds underlain by mineralized Sunsh

caldera.

U)

Tertiary basalts

Tertiary ash flow tuff

Tertiary latitic lava and breccia

Tertiary andesites

Tertiary sediments

Cretaceous Mesaverde Fm

Cretaceous Mancos Shale

Mesozoic sediments

Paleozoic sediments

Tertiary and Proterozoic rocks

Chloride

0.29

0.88

0.56

0.65

1.4

0.49

0.8

3.4

O.25

0.39

TDS

39.3

74.5

93

109.4

196

69.5

133.8

200.3

174

50.9

TDS/CI

133.8

84.7

166

155.5

144.6

141.5

222.2

58.1

714.6

131.5

Alkalinity

28

46

36

72

191

54

101

205

143

34

Alkalin

9

5

6

10

13

11

16

5

57

8

Sunshine Peak Tuff 0.12 66.4 552.4 3.9 3

Total dissolved solids (TDS) in mg/l, chloride, sulfate, and fluoride in mg/l, alkalinity in mg/l HC

in ug/l.
F

0.07

0.1

<0.1

0.07

0.16

0.11

0.12

0.12

<0.1

0.21

F/CI

0.24

0.11

0.125

0.1

0.11

0.22

0.2

0.03

0.28

0.54

U

0.069

0.058

0.14

0.092

1.4

0.13

0.27

2.7

0.56

0.78

U/CI

0.24

0.07

0.25

0.13

1

0.27

0.45

0.77

2.24

2

Li

0.3

1.5

3.6

1.3

7.2

1.4

1.6

12

2.1

1.7

Li/CI

1.03

1.7

6.4

1.86

5.14

2.86

2.67

3.43

8.4

4.36

0.17 1.41 0.66 5.49 3.7 31
rocks.

Mean concentrations of Cu, Mo, and As are low in waters from areas underlain by the 

Sunshine Peak Tuff, which is similar to that of waters from the GMUG watersheds. Mean Zn 

concentration of 11 [ig/1 is high compared to the GMUG watersheds in which the highest mean 

concentration of Zn is 0.64 [ig/1 from the Tertiary intrusive and Proterozoic rocks (Table 20). 

Mean U concentration of 0.66 [ig/1 in waters from areas underlain by the Sunshine Peak Tuff is 

elevated probably because of the felsic rock type, but not as high as Mesozoic and Tertiary 

sedimentary rocks and Tertiary intrusive and Proterozoic rocks (Table 20). Mean concentrations 

of Al and Mn are higher in waters from areas underlain by the Sunshine Peak Tuff, with mean 

concentrations of 420 and 40 [ig/1 compared to the GMUG waters (Table 20). Within the 

GMUG area, waters from areas underlain by Tertiary basaltic rocks contained the highest mean 

Al concentration of 54 [ig/1, nearly an order of magnitude less than waters from areas underlain 

by the Sunshine Peak Tuff. The weathering of the pyrite, present in the Sunshine Peak Tuff, 

releases acidity which mobilizes the Al in the waters. Within the GMUG area, waters from areas 

.underlain by Tertiary sedimentary rocks contained the highest mean Mn concentration of 4.7 

[ig/1, nearly an order of magnitude less than waters from areas underlain by the Sunshine Peak 

Tuff (Table 20). Mean Fe concentration of waters from areas underlain by the Sunshine Tuff 

area is SO [ig/1, which is elevated in concentration compared to the GMUG watersheds, but - 

waters from Tertiary basaltic rocks (91 j-ig/ll) and Tertiary ash-flow tuff (65 |ig/l) contained 

higher mean concentration of Fe.

Summary and Conclusions

This study determines, for mountainous headwater areas, the range of baseline 

geochemistry of stream and spring waters that evolve within each often major rock 

compositional types present in the Gunnison, Uncompahgre, and Grand Mesa National Forests. 

Processes responsible for the control and mobility of elements in water were investigated. By 

comparing the geochemistry of the waters that evolve in each of the dominant rock 

compositional types, conclusions can be drawn characterizing the rock compositional types as to 

their acid-neutralizing capacities and potential release of TDS or chemical weathering rates for 

each of the different rock compositional types. For each of the three National Forests, map plots 

showing potential release of TDS, mean pH values, and acid-neutralizing capacities, are made for 

each of the ten major rock compositional types. Also, processes responsible for the control and 

mobility of elements in water were investigated. In addition, the geochemistry of waters from 

the sampled watersheds in the GMUG, which are underlain by rocks that are relatively 

unmineralized, are compared to waters from the Redcloud Peak area, an adjacent area

75
administered by the BLM which has been mineralized and probably contains significant mineral 

deposits. The following are the most significant conclusions based on these results:

* 1 . The baseline geochemistry of stream and spring waters evolving in the mountainous 

headwater areas depends on the chemical composition of the underlying rock type. 

Within each rock compositional type, a unique range of water compositions evolve. 

Other factors such as annual precipitation, temperature, topographic setting, character of 

minerals, such as grain size and crystallinity, and biotic activity can be important, but 

mainly influence the rates of chemical reactions and not the type of elements present in 

the waters.

» 2. The waters that evolve in these headwater areas in GMUG are generally Ca2+- HCO3" 

type waters, with alkaline pH values, low to moderate total dissolved solids, and 

generally are of good chemical quality, with low concentrations of elements such as Cu, 

Zn, Mo, As, U, Al, Fe, and Mn. Some waters may have slightly elevated concentrations 

of some of these elements because of the presence of minerals such as pyrite. Dominant 

species present in most of the water samples are Ca2+, Mg 2+, Na+ , 1C, SO42~, HCO3 ', Cl~, 

F-, H4Si04°, A1(OH)4 -, Fe2+, and

3. Chloride concentrations of most of the waters from the three National Forest are 

generally low, which indicates considerable snowmelt component of stream waters. 

These mountainous headwater areas have shallow soil zones with minimal groundwater 

reservoirs. Therefore, except for the Mesozoic and Tertiary sedimentary rocks, the time 

of contact of water with the rocks is short and evaporation processes are minimal.

4. TDS values, which are measures of the chemical weathering rates, indicate that waters 

with the highest TDS values evolves from watersheds underlain by Mesozoic and 

Tertiary sedimentary rocks. Waters with the lowest TDS values evolve from watersheds 

underlain by Tertiary basaltic rocks and Tertiary intrusives and Proterozoic rocks. If TDS 

values are normalized by dividing by Cl concentrations and reducing the effects of time 

of contact of water and rock and evaporation processes, the rocks with the highest 

potential release of TDS are Paleozoic sedimentary rocks followed by the Mancos 

Formation, Tertiary sedimentary rocks, and the Mesaverde Formation. Potential release 

of TDS does not take into account the amount of precipitation of an area.

5. S.ulfate concentrations of waters from areas underlain by Paleozoic sedimentary rocks

76
reach up to several hundred mg/1. The high concentration of sulfate is probably due to 

the dissolution of gypsum present in the Permian and Pennsylvanian rocks. The 

Evaporite Facies to the north of the Gunnison National Forest contains gypsum and 

intertongues with the Minturn and Lower Maroon Formations (Tweto, 1979) present in 

the sampled watersheds.

6. Alkalinity is measure of the acid-neutralizing capacity of waters to introduced 

acidification. Waters from Mesozoic and Tertiary sedimentary rocks have the highest 

mean alkalinity values. The waters with the lowest mean alkalinity values and the most 

susceptible to introduced acidity are from the top of Grand Mesa, which is underlain by 

basaltic rocks, and areas underlain by Tertiary intrusive and Proterozoic rocks. When . 

alkalinity is normalized by dividing by Cl to reduce the effects of evaporation and time of 

contact of water and rocks, the waters with the highest mean normalized alkalinity are 

from watersheds underlain by Paleozoic sedimentary rocks followed by the Mancos Shale 

and Tertiary sedimentary rocks. The higher normalized alkalinity values of waters from 

watersheds underlain by these rocks are probably because of the presents of carbonate 

rocks and local calcareous zones present within these units. The watersheds underlain by 

these rock types have the greatest acid-neutralizing capacities and are the most resistant to 

introduced acidification from processes such as^ acid-mine drainage or dry fallout from 

coal-burning power plants. The waters with the lowest mean normalized alkalinity values 

are watersheds underlain by Tertiary ash-flow tuff and Tertiary intrusive and Proterozoic 

rocks, which are the most susceptible to introduced acidification.

7. The Tertiary sedimentary rocks contain oil shales which outcrop in some of the 

sampled watersheds. These rocks contain pyrite, generally with elevated metals. Sulfate 

is present in waters, up to 25 mg/1, from these watersheds, which probably indicates some 

weathering of pyrite, but enough calcareous material is present to generate alkalinity and 

consume the generated acidity. The higher pH values ensure that trace metals present as 

cations will form hydroxides or are adsorbed, so that their concentrations remain low. 

Arsenic, which is present as an anionic specie, is slightly elevated (up to 5.8 p.g/1), but 

overall, there is only slight impact of the oil shale on the chemical water quality in these 

mountainous headwater areas.

8. The Mesaverde Formation contains extensive coal deposits which contain pyrite. 

Sulfate is present in waters from these watersheds (up to 19 mg/1), probably from the 

weathering of pyrite, but pH values are alkaline, indicating any generated acidity is being

77
buffered by the alkalinity. The mean alkalinity value is moderately low at 54 mg/1 as 

HCO3 ", probably because of the acidity generated from weathering pyrite consumes some 

of the alkalinity. In addition, less calcareous material is probably present in the 

Mesaverde Formation to contribute alkalinity, compared to the other sedimentary rock 

units in the GMUG area. Overall, the chemical quality of the water from areas underlain 

by the Mesaverde Formation is good, but the unit is more susceptible to introduced 

acidification than the other sedimentary rock units in GMUG.

» 9. The Mancos Shale is marine in origin and contains black shale and associated pyrite 

and elevated trace metal values. Locally, calcareous-rich zones are present and high 

alkalinity is generated in waters from areas underlain by these rocks. The high alkalinity 

buffers any acidity generated by the oxidizing pyrite and reduces the mobility of trace 

metal cations because of the higher pH values. Se, present in the Mancos Shale, is known 

to reach elevated concentrations downstream from the headwater areas. Se 

concentrations in water are low (mean Se <0.2 |ig/l) in these sampled mountainous 

headwater watersheds underlain by the Mancos Shale. The high Se concentrations in 

waters in lower, more arid areas underlain by the Mancos Formation outside of the 

GMUG area are probably concentrated by evaporation effects. The waters from these 

mountainous headwater areas are well buffered and good in overall chemical quality.

* 10. The Mesozoic sedimentary rocks contain uranium concentrations which have been 

mined adjacent to the GMUG area, along the western flank of the Uncompahgre plateau. 

Waters from these rocks contain only slightly elevated concentrations of uranium (up to 

5.8 |ig/l) and represent no problem to water quality.

» 11. Cattle are heavily grazed in portions of the GMUG area. The cattle tend to

concentrate in wetlands of watersheds where their hoofs muddy and disturb the wetland 

surface. This physical disturbance, along with the cattle wastes, decrease the oxygen 

content of the water and cause more reducing conditions. One impact on water quality 

appears to be the increased mobility of Fe due to the more reducing conditions. But 

overall, the chemical quality of the waters is not significantly impacted.

The unique geochemical baselines from the ten rock compositional types demonstrates 

the importance of rock composition in determining the types of waters that are evolving in these 

mountainous headwater areas. These geochemical baselines provide a range of values that

78
approximate the natural background geochemistry of the stream and spring waters in these 

watersheds for each of the ten major rock composition types. In addition, the comparison of 

these geochemical baselines with future baselines will allow the recognition of any significant 

changes in water quality that may occur in the future.

79
References Cited

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implications on water quality, Upper Colorado River Basin, Colorado and Utah: WaterResources Investigations Report 95-4263, 33 p.

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encrustation effects on wells: U.S. Geol. Survey Professional Paper 498-D, 58 p.

Benci, J.F and McKee, T.B., 1977, Colorado monthly temperature and precipitation summary for 

period 1951-1970: Fort Collins, Colorado State University, Climatology Report 77-1, 

300 p.

Benedict, A.D., 1991, The Southern Rockies: Sierra Club Books, San Francisco, 578 p.

Bradley, W. H., 1964, Geology of the Green River Formation and associated Eocene rocks in 

southwestern Wyoming and adjacent parts of Colorado and Utah: U. S. Geological 

Survey Professional Paper 496-A, 86 p.

Colorado Climate Center, 1984, Colorado average annual precipitation 1951-1980: Compiled by 

Colorado Climate Center, Dept. Atmospheric Science, Colorado State Univ., Fort 

Collins, scalel:500,000.

Edwards, T. K. and Glysson, G. D., 1988, Field methods for measurement of fluvial sediment: 

U.S. Geological Survey Open-File Report 86-531, 118 p.

Fishman, M.J. and Pyen, G., 1979, Determination of selected anions in water by ion 

chromatography: U.S. Geol. Survey Water Resources Invest. 79-101, 30 p.

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Verlag, 486 p.

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River Formation oil shale, Wyoming, Utah, and Colorado: in Geochemical, 

biogeochemical, and sedimentological studies of the Green River Formation, Wyoming,

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Utah, and Colorado, edit, M..L. Tuttle, U.S. Geological Survey Bulletin 1973, Dl- D18.

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Geological Survey Water-Supply Paper 2254, 263 p.

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Freeman and Company, 725 p.

Lipman, P.W., 1976, Geologic map of the Lake City caldera area, western San Juan Mountains, 

southwestern Colorado: U.S. Geological Survey Miscellaneous Investigations Series Map 

1-962, scale 1:48,000.

Livingstone, D.A., 1963, Chemical composition of rivers and lakes: 6th ed., U.S. Geological 

Survey Professional Paper 440-G, p.

Miller, W.R. and McHugh, J.B., 1998, Geochemical baselines and processes affecting surface 

water, Redcloud Peak area, Colorado: U.S. Geological Survey Open-File Report 98-35, 

20 p.

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Parkhurst, D.L., 1995, User's guide to PHREEQC - a computer program for speciation, reactionpath, advective-transport, and inverse geochemical calculations: U.S. Geological Survey 

Water-Resources Investigations Report 95-4227, 143 p

Roehler, H. W., 1974, Depositional environments of rocks in the Piceance Creek basin,

Colorado: in Energy resources of the Piceance Creek basin, Colorado, edit, D. K. Murray, 

Twenty-fifth field conference, Rocky Mountain Association of Geologist, p. 57-69.

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River Formation, Wyoming, Utah, and Colorado: U.S. Geological Survey Bulletin 1973 

A-G,A1-A5.

Tweto, O, 1976, Preliminary geologic map of the Montrose 1° x 2 ° quadrangle, southwestern 

Colorado: Misc. Field Studies Map MF-761, 1:250,000.

81
Tweto, 1979, Geologic map of Colorado: U.S. Geological Survey Publication, scale 1:1,500,000. 

U. S. Department of Agriculture, 1972, Natural vegetation , Colorado, scale 1:1,500,000.

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City, Utah, Management of Irrigated and Drainage System, p. 770-777.

82
Appendix 1. Chemical analyses of stream and spring waters from watersheds underlain by the ten dominant rock co

Gunnison, Grand Mesa, and Uncompahgre National Forests

00 

U)

Sample No.

Deg.

Latitude

Min. Sec. Deg.

Longitude

Min. Sec.

D

' Tertiary basalt

G14

G15

G16

G17

39

39

39

38

1

0

0

0

58

34

3

7

108

108

108

108

10

11

10

9

34

29

36

41

basalti

basalti

basalti

basalti

Tertiary ash flow tuff

G45

G46

G56

G57

G58

38

38

38

38

38

12

10

8

4

6

6

20

29

56

12

106

106

106

106

106

50

51

48

50

49

53

15

23

2

30

Tertiary quartz latite

C12

C13

C14

C15

38

38

38

38

0

0

1

1 -

31

38

15

20

107

107

107

107

2

2

2

2

13

23

18

23

quartz 

quartz 

quartz 

quartz 

Tertiary andesite

G47

G48

G49

G50

G51

G52

G54

G55

38

38

38

38

38

38

38

38

38

36

35

34

34

33

32

30

49

23

11

39

25

35

45

42

106?

107

107

107

107

107

107

107

19

19

20

19

20

19

19

18

17

58

14

59

1

43

19

53

andesit

andesit

andesit

andesit

andesit

andesit

andesit

andesit
00

Tertiary sedimentary rock

G01

G02

G03

G04

G05

G06

G07

39

39

39

39

39

39

39

17

14

20

20

199

12

1

46

26

19

12

17

18

107

107

107

107

107

107

107

34

41

50

50

57

55

48

501

336

105

46

cla

cla

shale, sa

shale, sa

shale, oil s

oil shale

shale, sa

G32

G33

G34

G35

G36

G37

G38

G39

38

38

38

38

38

38

38

38

48

48

48

50

50

52

55

55

45

49

43

37

36

38

17

44

Cretaceous

107

107

108

107

107

107

107

107

Mesaverde

18

18

18

19

19

20

20

20

Formation

45

44

207847

18

s

s

s

s

s

s

s

s

Cretaceous Mancos

G19

G20

G24

G25

G26

G27

G28

G29

G30

G31

38

38

37

37

37

37

37

37

37

37

48

48

55

53

53

54

54

54

54

53

178

41

31

178

32

103

29

107

107

108

108

108

108

108

108

108

108

33

33

12

12

11

14

10

1097

Shale

29

56

200

520

45

30

310
oo

Mesozoic sedimentary rock

G09

G10

G11

G12

G13

38

38

38

38

38

44

44

40

38

35

41

48

598

25

108

108

108

108

108

32

33

41

41

38

59

23

25

22

56

sandstone, siltst

sandstone, siltst

sandstone, s

sands

sands

C01

C02

COS

C04

COS

C06

C07

COS

C09

C10

C11

C16

C17

C18

C19

38

38

38

38

38

38

38

38

38

38

38

38

38

38

38

49

50

51

52

53

53

57

57

56

55

54

51

49

49

49

31

44

32

175

38

55

37

58

50

37

23

54

32

10

Paleozoic

106

106

106

106

106

106

106

106

106

106

106

106

106

106

106

sedimentary

50

49

48

47

47

46

46

46

46

46

46

42

43

43

44

rock

54

13

19

52

25

55

11

13

18

10

56

42

10

42

17

sandstone, gr

andstone, cong, 

sandston

sandston

sandston

sandston

sandston

sandston

sandston

sandston

sandstone, grit

sandstone, grit

sandstone, grit

carbonate, san

Tertiary and Proterozoic

G21

G22

G23

G40

G41

G42

G43

G44

38

38

38

38

38

38

38

38

26

31

31

34

34

35

37

37

31

46

57

10

466

36

42

106

106

106

106

106

106

106

106

21

24

24

33

32

32

25

24

rock

47

199

35

32

18

19

22

granite, q

granite , int

granite , int

felsi

granite, q

granite, q
oo

Water Type Flow Comments Temperature

deg.C

PH 

Tertiary basalt

unnamed stream

Coal Ck

unnamed stream

unnamed stream

2 pt/min

2 qt/sec

2-3 cfs

2-4 gal/sec

nearly dry

some cows

yell, ting, from wetlands

from wetlands, good sample

13.6

13.1

9.5

12.7

7.09

7.37

7.67

7.49

Tertiary ash flow tuff

spring

Blue Ck

spring

Perfecto Ck

Pauline Ck

1-2 pt/sec

1-2 gal/sec

1/2 -1 pt/sec

1/2 -2 cfs

5-7 cfs

clear, drift - pH

v. hard to filter, wetlands, si. sed.

steel pipe, clear

si yell bn color, mod hard to filter, old cattle signs, + drift

si yell color, hard to filter

8.7

13.1

6

10.6

10.9

7.40

8.02

6.89

7.37

7.46

Tertiary quartz latite

Mineral Creek

small stream

small stream

small stream

1 00 gal/sec

0.25 gal/sec

4gal/sec

4 gal/sec

nearly clear, some sediments in water, hard to filter

sediments, hard to filter, rain

silt, hard to filter, rain

silty from raising stream, rain

7.4

7

5.7

7.7

7.4

7.35

7.4

7.75

Tertiary andesite

W. Soap Ck

Lion Gulch

unnamed stream

unnamed stream

unnamed stream

unnamed stream

Oregon Gulch

Chance Gulch

2-4 cfs

1 pt/sec

1 pt/sec

1 gal/sec

1-2 pt/sec

2 pt/sec

5-1 0 gal/sec

1 gal/sec

clear

clear

flow intermid. in bed

clear

clear but hard to filter

clear

clear, + drift

si hard to filter, + drift, si orange color

12.4

12.3

16.2

11.8

10.9

12.4

11.4

13.5

7.49

8.20

8.53

7.93

7.97

8.06

7.90

7.86
oc

Tertiary sedimentary rock

Hightower Ck?

unnamed stream

W. Bush Ck

E. Bush Ck

Kimball Ck

unnamed stream

Park Ck

1-2qt/sec

2-4 pt/sec

2cfs

3-4 cfs

!4-1 gal/sec

2 cfs

3-5 cfs

hard to filter, cattle

si. sed, cattle

v. si. sed, cattle

min. cattle

si. hard to filter

21.6

23.5

16

14.8

9.1

12.9

13.4

8.46

8.69

8.51

8.65

8.47

8.16

8.55

Cretaceous Mesaverde Formation

Coal Ck

Robenson Ck

spring

Cliff Ck

Coal Ck

Coal Ck

Coal Ck

5-10 cfs

1-2 cfs

1 pt/sec

10 cfs

10-1 5 cfs

25 cfs

25-30 cfs

8-10 cfs

si. murky w/ sed.

v. si. murky w/ sed.

v. clear

clear

mod. sed., hard to filter

si. murky

mod. clear, drift +

drift + pH

11.1

15.7

11.3

11.9

13.3

14

17.7

20

8.36

8.57

8.00

8.10

8.30

8.36

8.26

8.54

Cretaceous Mancos Shale

spring

springs

unnamed stream

W. Fk Beaver Ck

E. Fk Beaver Ck

unnamed stream

unnamed stream

Beaver Ck

Spring Ck

McCullach Ck

qt/sec

2-3 qt/sec

2 cfs

1-2 cfs

2-3 cfs

1-2 gal/sec

2-4 qt/sec

1 gal/sec

1/2 -1 gal/sec

2 gal/sec

series of springs, cattle

series of springs, cattle in area

mod. hard to filter, si. sed

clear

cleat

v. clear

drainage from wetlands, some cattle, prob. good sampi

cattle impacted, meadows

clear

clear

11.4

9.7

13.5

13.4

7.6

8.6

20.2

22

16.1

11.8

7.46

8.17

8.14

8.26

8.26

8.16

8.22

8.48

8.58

8.29
oo 

oo

Mesozoic sedmentary rock

Big Dominquez Ck

spring

spring

spring

California Spring

3cfs 1/2 -1 pt/sec

1-2 gal/sec

1 qt/sec

1 qt/sec

galv. pipe coated w/ carb.

good sample

good sample

pvc pipe

13.7

11.4

7.2

6.6

4.9

8.53

8.25

7.74

7.48

7.71

Paleozoic sedimentary rock

Walrod Gulch

small stream

small stream

small stream

small stream

small stream

Upper Cement Ck

small stream

small stream

small stream

small stream

small stream

spring

small stream

Deadman Gulch

5 gal/sec

2 gal/sec

4 gal/sec

10 gal/sec

7 gal/sec

7 gal/sec

1 gal/sec

0.75 gal/sec

10 gal/sec

5 gal/sec

8 gal/sec

1 0 gal/sec

1 gal/sec

2 gal/sec

25 gal/sec

some silt

abund. cream coatings

some silt

clear, Marron Fm

Marron Fm

clear, Marron Fm, some igneous float

mine above, Is, qtzite, igneous

wet land, sh, cong float

silicious sed otc

silicious sed otc, some igneous float

clear, abund igneous float, also sed

sed and igneous float, pH drifting up

coming from wetland, pH drifting up

clear, sed float, pH drifting up

clear, pH drifting up

8.6

12.4

8.8

7.6

7.2

8.1

11.2

11.5

9.4

7.39

5.7

10.7

11.5

11.5

8.33

8.23

8.36

8.13

8.25

8.4

8.14

8.17

8.44

8.38

8.39

8.2

7.97

8.47

8.59

Tertiary and Proterozoic rock

spring

unnamed stream

Spring Ck

unnamed stream

unnamed stream

unnamed stream

Fitz patrick Gulch

Tunnel Gulch

2-4 gal/min

2 gal/sec

1 gal/sec

1 qt/sec

1 pt/sec

1 qt/sec

1-2cfs

1 cfs

steel pipe

clear

clear

clear

clear

clear

clear

clear

7.7

11.29

12.1

10.3

10.8

6.5

7.3

6.89

7.63

7.79

8.14

8.18

8.18

8.00

7.75
Ca

mg/L

Mg

mg/L

Na

mg/L

K

mg/L

Si02

mg/L

Alkalinity SO4 Cl

mg/L HCO3 mg/L mg/L

F

mg/L

N (nitrate)

mg/L

H

Tertiary basalt

4.05

5.89

6.10

5.65

1.77

2.24

2.29

2.13

1.5

1.92

2.02

1.92

0.2

0.4

0.5

0.4

10.9

13.7

19.0

14.9

24

30

30

30

1.60 0.31

0.378 0.60

0.638 <0.25

0.453 <0.25

<0.10

<0.10

<0.10

<0.10

O.125

O.125

O.125

O.125

Tertiary ash flow tuff

16.5

13.3

14.4

5.30

8.44

2.80

1.71

2.03

0.826

1.63

5.12

7.86

3.7

3.47

3.1

1

2

1

1

0.9

39.6

41.2

32.6

20.8

19.2

70

52

54

32

34

3.85 1.9

5.96 1.3

2.13 1.1

1.37 0.55

2.07 0.37

0.14

0.13

0.11

<0.10

<0.10

0.172

<0.125

<0.125

<0.125

<0.125

Tertiary quartz latite

15.7

8.74

14.5

12.7

2.58

0.78

2.94

1.92

3.67

13

7.94

6.14

1.17

2.19

0.688

0.878

9.49

26.1

12.3

14.2

29

35

44

36

27.9 <0.25

10.4 1.50

17.1 0.56

15.2 0.58

<0.1

<0.1

<0.1

<0.1

<0.1

<0.1

<0.1

<0.1

7

3

5

5

Tertiary andesite

19.3

9.95

11.4

22.2

21.5

14.8

16.5

18.9

3.32

1.74

1.66

7.72

4.20

2.84

3.03

2.33

7.28

14.8

4.91

12.4

5.68

11.1

5.55

5.54

2

1

0.8

2

2

2

2

2

39.4

31.6

21.9

34.7

29.5

35.0

47.4

48.1

32 14.0 0.34

102 22.5 0.82

84

80

68

82

72

78

5.16 0.70

1.88 0.70

2.74 0.76

2.58 0.71

1.36 0.81

0.757 0.99

<0.10

<0.10

0.11

<0.10

0.14

<0.10

0.10

<0.10

<0.125

<0.125

<0.125

O.125

0.136

O.125

<0.125

O.125
Tertiary sedimentary rock

62.3

42.7

31.4

44.5

56.1

18.2

37.0

11.4

36.9

6.61

11.5

12.6

7.84

10.2

20.5

45.1

9.31

14.1

32.2

5.21

7.25

4

3

0.7

0.6

0.8

2

1

6.5

19.6

17.2

19.8

26.8

26.1

16.9

250

352

160

182

242

92

160

14.0

5.34

7.39

10.3

25.4

3.36

4.82

8.3

3.4

0.63

0.69

1.3

0.75

0.72

0.51

0.17

0.11

0.14

0.21

0.07

0.15

<0.125

<0.125

<0.125

<0.125

<0.125

<0.125

<0.125

12.9

30.5

23.8

7.67

13.5

10.6

10.8

8.83

2.86

7.85

8.29

1.31

3.06

2.16

2.22

1.67

4.43

8.41

13.4

4.25

4.22

4.39

4.88

3.8

0.5

0.8

0.3

0.4

0.5

0.4

0.4

0.6

13.8

10.7

13.1

14.5

11.9

12.8

12.7

12.6

Cretaceous

44

122

112

34

52

40

42

40

Mesaverde

8.71

19.2

7.81

1.48

8.46

4.65

4.81

1.67

Formation

0.33

1.0

0.99

0.25

0.40

0.37

0.49

0.57

<0.10

0.16

0.11

<0.10

<0.10

<0.10

<0.10

<0.10

<0.125

<0.125

<0.125

<0.125

<0.125

<0.125

<0.125

<0.125

2

Cretaceous Mancos Shale

27.4

50.3

48.2

41.9

12.0

32.3

32.4

33.6

47.0

22.0

6.42

13.3

10.6

7.64

2.26

11.1

5.23

8.32

10.6

7.18

6.61

12.8

3.99

3.46

2.71

3.01

4.87

6.97

5.91

2.53

0.2

0.2

0.7

0.5

0.2

0.2

1

0.5

0.5

0.4

21.6

27.1

12.0

8.6

9.5

12.1

9.5

15.7

16.2

9.5

88

162

168

120

30

106

84

144

180

58

17.5

27.2

16.1

25.9

13.9

29.0

34.7

6.06

6.16

36.5

0.97

1.9

0.59

0.40

0.26

0.45

0.38

1.0

1.0

0.31

0.10

0.14

0.15

0.16

<0.10

<0.10

0.19

0.13

0.14

<0.10

<0.125

<0.125

<0.125

<0.125

<0.125

<0.125

<0.125

<0.125

<0.125

<0.125
43.5

60.6

83.8

73.1

43.6

7.43

13.5

10.8

11.3

9.14

3.38

10.3

3.51

2.02

14.9

2

2

1

2

3

6.9

16.9

9.1

7.8

19.0

Mesozoic

152

214

262

246

172

sedmentary rock

2.50 2.5

7.94 6.1

5.16 5.8

3.17 1.6

7.05 3.5

0.12

0.13

0.15

0.15

<0.10

O.125

O.125

0.316

0.153

0.445

55.3

51.2

44.2

40.6

44.1

47.2

63.4

57.4

101

63.7

44.5

44.3

64.3

47

44.4

20.4

25

14.2

2.94

3.29

4.17

16.3

17

19.5

20.1

10.6

4.83

17.6

12.9

11.3

5.38

1.21

1.66

0.945

1.59

1.73

0.609

0.61

0.742

0.773

1.18

1.49

2.07

1.68

0.977

1.33

0.79

0.574

0.201

0.288

0.496

0.231

0.108

0.598

0.723

0.451

0.603

0.626

1.13

0.371

6.29

6.89

7.02

4.88

7.23

7.27

4.71

4.41

3.72

4.86

5.99

9.60

8.62

11.64

5.88

Paleozoic

180

194

148

110

120

138

178

165

118

138

139

112

169

138

135

sedimentary rock

33.5 1.69

32.4 0.44

8.0 0.2

0.8 0.2

1.6 0.2

1.1 0.2

52.0 0.2

40.4 0.2

203.6 0.2

102.2 0.2

6.1 0.2

3.8 0.2

47.4 0.2

17.2 0.2

7.8 0.2

0.2

<0.1

0.1

0.1

0.1

O.1

O.1

O.1

O.1

O.1

O.1

0.1

0.1

O.1

O.1

0.2

0.2

O.1

O.1

0.1

O.1

O.1

O.1

O.1

O.1

O.1

O.1

O.1

O.1

O.1

1

<

0

4

<

<

0

<

0

<

0

<

7

<

0

Tertiary and Proterozoic rock

5.89

6.41

11.8

9.38

10.3

9.70

5.81

7.05

1.24

1.13

4.09

2.86

3.93

4.03

0.555

0.507

5.01

3.23

3.59

3.03

5.27

5.05

1.58

1.15

0.6

0.8

0.6

0.7

0.6

0.6

0.4

0.2

22.3

15.9

21.3

13.2

19.4

16.9

9.0

6.1

28

20

42

50

50

48

26

26

4.09 0.90

9.83 0.27

14.7 0.36

3.58 0.49

2.38 0.55

2.70 0.54

1.03 O.25

1.56 <0.25

O.10

O.10

O.10

0.69

1.8

2.2

O.10

O.10

O.125

O.125

O.125

O.125

O.125

O.125

O.125

O.125
Ba Be Cd Co Cu Li Ni Sr Ti Zn V 

ng/L ng/L ng/L ng/L ng/L ng/L ng/L |ig/L ng/L ng/L ng

17

14

10

15

<0.05

<0.05

<0.05

<0.05

<0.5

<0.5

<0.5

<0.5

<0.5 <1

<0.5 <1

<0.5 <1

<0.5 <1

<0.5

<0.5

<0.5

<0.5

Tertiary

<2

<2

<2

<2

basalt

29

39

38

37

4

2

<2

<2

0.4

0.5

0.4

0.3

<0

<0

0.5

<0

Tertiary ash flow tuff

25

19

32

10

12

<0.05

<0.05

<0.05

<0.05

0.06

<0.5

<0.5

<0.5

<0.5

<0.5

<0.5 <1

<0.5 <1

<0.5 <1

<0.5 <1

<0.5 <1

2

3

2

0.9

0.9

<2

<2

<2

<2

<2

107

109

79

47

72

<2

<2

<2

<2

<2

0.3

0.2

<.2

0.3

0.3

<0

3.3

2.3

0.7

1.2

Tertiary quartz latite

13.2

3.54

2.59

3.81

<0.05

0.1

<0.05

<0.05

<0.5

<0.5

<0.5

<0.5

0.07 0.76

0.09 0.74

0.04 < 0.5

0.05 0.60

1.7

10.0

3.0

3.4

0.4

0.4

0.3

0.4

171

57.6

163

109

0.5

7.6

1.9

1.4

0.6

1

0.5

<0.5

0.

1.

1.

1.

Tertiary andesite

6

1

3

5

9

6

8

8

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

<0.5

<0.5

<0.5

<0.5

<0.5

<0.5

<0.5

<0.5

<0.5 <1

<0.5 <1

<0.5 <1

<0.5 <1

<0.5 <1

<0.5 <1

<0.5 <1

<0.5 <1

1

1

0.8

3

1

0.9

1

2

<2

<2

<2

<2

<2

<2

<2

<2

112

60

62

97

149

121

100

92

<2

<2

<2

<2

<2

<2

<2

<2

<.2

<2

0.2

0.3

0.4

0.3

<.2

0.2

0.8

2.0

2.6

2.3

2.9

2.6

2.6

2.6
Tertiary sedimentary rock

208

118

42

36

44

32

69

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

<0.5

<0.5

<0.5

<0.5

<0.5

<0.5

<0.5

<0.5

<0.5

<0.5

<0.5

<0.5

<0.5

<0.5

21

<1

<1

<1

<1

<1

3

2559

171

12

<2

<2

<2

<2

<2

<2

<2

348

718

202

326

452

114

337

<2 0.5

<2 0.3

<2 <.2

<2 <2

<2 <.2

<2 0.2

<2 0.3

1.5

4.1

3.1

4.4

5.5

2.1

1.2

Cretaceous Mesaverde Formation

11

49

35

11

14

12

14

29

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

<0.5

<0.5

<0.5

<0.5

<0.5

<0.5

<0.5

<0.5

<0.5

<0.5

<0.5

<0.5

<0.5

<0.5

<0.5

<0.5

<1

<1

<1

<1

<1

<1

<1

<1

152

0.7211

0.8

<2

<2

<2

<2

<2

<2

<2

<2

82

226

364

52

89

70

74

75

<2 0.3

<2 0.3

<2 <.2

<2 0.2

<2 0.2

<2 0.3

<2 0.2

<2 0.4

<0

<0

<0

0.7

<0

<0

<0

0.7

14

35

35

2075

26

21

29

16

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

<0.5

<0.5

<0.5

<0.5

<0.5

<0.5

<0.5

<0.5

<0.5

<0.5

<0.5

<0.5

<0.5

<0.5

<0.5

<0.5

<0.5

<0.5

<0.5

<0.5

<1

<1

<1

<1

<1

<1

<1

<1

<1

<1

2222

0.9

<0.5 6121

Cretaceous

<2

<2

<2

<2

<2

<2

<2

<2

<2

<2

Mancos Shale

241

581

192

141

39

190

174

176

194

111

<2 0.5

<2 0.2

<2 0.2

<2 0.2

<2 <.2

<2 <2

<2 0.4

<2 <.2

<2 <.2

<2 <.2

0.7

0.7

<0

<0

<0

<0

<0

<0

1.7

<0
257

227

439

274

274

<0.05

<0.05

<0.05

<0.05

<0.05

<0.5

<0.5

<0.5

<0.5

<0.5

<0.5

<0.5

<0.5

<0.5

<0.5

1

<1

<1

<1

<1

8

11

20

15

11

Mesozoic

<2

<2

<2

<2

<2

sedmentary rock

161 <2

241 <2

192 <2

205 <2

535 <2

0.3

0.2

0.3

<.2

0.3

0.5

2.7

1.0

<0

<0

108

61.3

72.9

99.0

169

264

64.0

55.7

54.6

53.5

134

84.5

73.7

85.3

102

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

-

-

-

-

-

0.06

0.05

0.06

0.05

0.05

0.06

0.07

0.07

0.10

0.06

0.06

0.04

0.12

0.06

0.06

0.63

<0.5

<0.5

<0.5

<0.5

<0.5

<0.5

<0.5

0.72

0.52

<0.5

<0.5

<0.5

<0.5

<0.5

Paleozoic

14.5 1.2

4.5

2.6

0.6

1.0

1.6

1.2

1.5

1.8

2.0

1.6

2.3

3.5

3.4

1.2

1.2

0.9

1.0

1.0

1.1

1.5

1.4

2.3

1.6

,1.1

0.9

1.6

1.1

'1.0

sedimentary rock

142 0.7

129 0.6

56.2 0.1

25.5 <0.1

47.0 <0.1

94.5 <0.1

123 0.8

143 0.7

793 3.1

419 1.6

70.0 0.1

38.0 <0.1

246 1.1

133 0.2

47.5 <0.1

1

0.5

0.5

<0.5

<0.5

0.6

0.9

0.7

0.7

0.8

0.6

<0.5

4.7

<0.5

<0.5

1

0.

0.

0.

1

1

0.

0.

0.

0.

1

0.

0.

0.

0.

Tertiary and Proterozoic rock

5

13

9

11

29

20

3

3

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

<0.5

<0.5

<0.5

<0.5

<0.5

<0.5

<0.5

<0.5

<0.5

<0.5

<0.5

<0.5

<0.5

<0.5

<0.5

<0.5

<!

<1

<1

<1

<1

<1

1

<1

6

2

2

0.7

2

1

1

1

<2

<2

<2

<2

<2

<2

<2

<2

36 <2

48 <2

36 <2

36 <2

31 <2

28 <2

37 <2

45 <2

0.6

4

5

0.4

0.3

0.2

0.3

0.3

<0

 <0

<0

<0

0.5

<0

0.5

<0
As Se Br Rb Y Zr Mo Sn Sb I C

(ig/L (ig/L (ig/L (ig/L (ig/L (ig/L (ig/L (ig/L ng/L (ig/L ^g

Tertiary basalt

<0.03

0.7

<0.03

<0.03

<0.2

<0.2

<0.2

<0.2

<3

<3

<3

<3

0.294

0.350

1.340

0.438

0.31

0.44

0.53

0.38

0.282

0.431

1.027

0.277

0.53 <0.05

<0.5 1.913

<0.5 <0.05

<0.5 <0.05

<0.01

0.22

<0.01

<0.01

<0.2

19.64

2.05

<0.2

<0.0

<0.0

<0.0

<0.0

Tertiary ash flow tuff

0.9

2.2

1.5

0.9

0.8

<0.2

<0.2

<0.2

<0.2

<0.2

33

<3

<3

<3

<3

0.764

2.248

0.327

3.118

1.609

0.08

0.08

0.05

0.14

0.18

0.220

0.843

8.512

0.124

0.178

<0.5 <0.05

0.60 <0.05

<0.5 <0.05

<0.5 <0.05

<0.5 <0.05

0.09

0.13

<0.01

<0.01

<0.01

7.82

5.17

3.51

<0.2

2.51

<0.0

<0.0

<0.0

<0.0

<0.0

Tertiary quartz latite

-

_

- -

3.05

1.51

0.85

1.07

0.10

1.49

0.28

0.24

- 0.08

1.4

0.3

0.3

0.26

0.82

1.08

0.37

<0.1

< 0.1

< 0.1

<0.1

_

-

-

0.0

0.0

0.0

0.1

Tertiary andesite

0.4

0.7

0.6

0.6

1.3

0.8

0.5

1.0

<0.2

<0.2

<0.2

<0.2

<0.2

<0.2

<0.2

<0.2

<3

<3

<3

<3

<3

<3

<3

<3

1.420

1.712

2.122

3.165

2.032

2.759

3.717

3.705

0.07

0.07

0.10

0.11

0.07

0.06

0.05

0.05

0.171

0.426

0.277

0.153

0.256

0.374

0.227

0.449

<0.5 <0.05

<0.5 <0.05

<0.5 <0.05

<0.5 <0.05

0.53 <0.05

0.59 <0.05

<0.5 <0.05

<0.5 <0.05

<0.01

<0.01

0.07

0.06

<0.01

<0.01

<0.01

<0.01

<0.2

<0.2

<0.2

<0.2

<0.2

<0.2

<0.2

2.16

<0.0

<0.0

<0.0

<0.0

<0.0

<0.0

<0.0

<0.0
Tertiary sedimentary rock

1.3

1.4

2.4

4.1

5.8

0.6

1.3

<0.2

<0.2

<0.2

<0.2

<0.2

<0.2

<0.2

90

182

<3

<3

<3

<3

<3

0.658

0.840

0.569

0.490

0.600

0.733

0.403

0.17

0.06

0.07

0.06

0.05

0.10

0.12

1.256

0.762

0.182

0.685

0.220

0.139

0.628

0.53

2.10

3.28

2.51

7.48

1.54

0.82

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

0.17

0.26

0.13

0.26

0.29

0.09

<0.01

35.69

24.76

2.45

<0.2

<0.2

<0.2

2.27

0.00

<0.0

<0.0

<0.0

<0.0

<0.0

<0.0

Cretaceous Mesaverde Formation

<0.03

0.3

<0.03

<0.03

2.4

<0.03

0.6

<0.03

<0.2

<0.2

<0.2

<0.2

<0.2

<0.2

<0.2

<0.2

<3

<3

<3

<3

<3

<3

<3

<3

0.398

0.306

0.136

0.350

0.447

0.429

0.365

0.279

0.04

0.04

<0.03

0.03

0.04

0.04

0.06

0.12

0.623

0.116

0.241

0.485

<0.05

<0.05

0.057

0.500

<0.5

<0.5

<0.5

<0.5

<0.5

<0.5

0.63

<0.5

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

<0.01

<0.01

<0.01

<0.01

<0.01

<0.01

<0.01

<0.01

<0.2

<0.2

<0.2

<0.2

<0.2

<0.2

<0.2

<0.2

<0.0

<0.0

<0.0

<0.0

<0.0

<0.0

<0.0

<0.0

0.4

0.3

0.5

0.4

<0.03

<0.03

<0.03

0.5

0.3

<0.03

<0.2

<0.2

<0.2

<0.2

<0.2

<0.2

<0.2

<0.2

<0.2

<0.2

<3

<3

<3

<3

<3

<3

<3

<3

<3

<3

0.071

0.078

0.227

0.249

0.153

0.052

0.653

0.230

0.238

0.163

0.04

0.04

0.04

0.09

0.06

0.03

0.13

0.05

0.05

0.06

0.415

<0.05

0.141

<0.05

0.069

0.070

0.064

0.073

0.055

<0.05

Cretaceous

0.80

0.72

0.80

0.81

<0.5

<0.5

1.35

1.28

1.74

<0.5

Mancos Shale

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

-0.01

0.01

0.07

0.14

0.06

<0.01

0.01

<0.01

<0.01

<0.01

2.32

3.63

3.85

<0.2

<0.2

<0.2

<0.2

3.24

<0.2

<0.2

<0.0

<0.0

<0.0

<0.0

<0.0

<0.0

<0.0

<0.0

<0.0

<0.0
Mesozoic sedimentary rock

2.8

2.0

1.8

0.3

0.6

<0.2

<0.2

2.71

<0.2

<0.2

<3

78

51

<3

<3

1.508

2.741

4.048

3.455

1.466

0.03

<0.03

<0.03

<0.03

0.20

0.241

0.083

0.440

0.232

<0.05

0.65

<0.5

<0.5

<0.5

<0.5

<0.05

<0.05

<0.05

<0.05

<0.05

0.01

<0.01

0.09

<0.01

0.06

2.67

5.53

2.78

<0.2

<0.2

<0.0

0.2

0.3

0.1

0.0

Paleozoic sedimentary

_

-

-

-

-

-

-

-

-

-

-

_

-

-

-

-

-

-

-

-

-

-

-

_

-

-

-

-

-

-

-

-

-

-

-

-

3.05

0.88

0.53

0.18

0.16

0.32

0.05

0.11

0.49

0.61

0.21

3.13

1.02

2.10

0.39

0.02

<0.01

0.02

0.08

0.04

0.05

0.03

0.02

0.10

0.03

0.04

0.05

0.04

0.03

0.04

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

0.68

0.91

0.48

<0.2

<0.2

<0.2

0.73

0.66

0.84

1.46

0.26

<0.2

0.45

0.51

0.25

-

-

-

-

-

-

-

rock

0.20

<0.1

<0.1

<0.1

<0.1

<0.1

<0.1

<0.1

<0.1

<0.1

<0.1

<0.1

<0.1

<0.1

<0.1

-

-

-

-

-

-

-

0.1

<0.0

<0.0

<0.0

<0.0

<0.0

<0.0

<0

<0.0

<0.0

<0.0

0.0

<0.0

<0.0

<0.0

Tertiary and

<0.03

<0.03

<0.03

<0.03

<0.03

<0.03

<0.03

<0.03

<0.2

<0.2

<0.2

<0.2

<0.2

<0.2

<0.2

<0.2

<3

<3

<3

<3

<3

<3

<3

<3

0.121

1.489

0.720

0.187

0.247

0.182

0.336

0.636

0.77

0.17

<0.03

0.65

0.37

0.77

0.03

0.04

0.571

0.084

0.175

0.366

0.110

0.085

12.503

0.678

<0.5

<0.5

0.72

1.26

1.40

2.90

<0.5

2.21

Proterozoic

<0.05

<0.05

<0.05

<0.05

1.475

<0.05

<0.05

<0.05

rock

<0.01

<0.01

<0.01

<0.01

0.13

<0.01

<0.01

0.15

3.16

<0.2

<0.2

<0.2

<0.2

<0.2

<0.2

<0.2

<0.0

<0.0

<0.0

<0.0

<0.0

<0.0

<0.0

0.03
OO

Nd

H9/L

Sm

H9/L

Eu

ng/L

Gd

ng/L

Tb

ng/L

Dy

ng/L

Ho Er

ng/L \igii

Tm

ng/L

Yb

H9/L

Lu

ng/

Tertiary basalt

0.331

0.425

0.314

0.335

0.053

0.063

0.040

0.053

0.025

0.037

0.031

0.017

0.132

0.105

0.136

0.060

<0.001

0.014

0.021

<0.001

0.048

0.088

0.078

0.037

<0.001 0.036

<0.001 0.057

0.019 0.043

<0.001 0.029

<0.001

<0.001

<0.001

<0.001

0.027

0.033

0.041

<0.001

<0.0

<0.0

<0.0

<0.0

Tertiary ash flow tuff

0.054

<0.004

<0.004

0.143

0.123

-0.001

-0.001

0.012

O.001

<0.001

<0.001

<0.001

<0.001

<0.001

<0.001

0.020

0.026

0.027

0.038

0.038

0.001

<0.001

<0.001

<0.001

<0.001

0.011

O.001

<0.001

0.011

0.022

<0.001 <0.001

<0.001 <0.001

<0.001 <0.001

<0.001 0.011

<0.001 0.014

0.001

<0.001

<0.001

<0.001

<0.001

<0.001

<0.001

0.014

0.021

0.024

<0.0

0.0

<0.0

<0.0

<0.0

Tertiary quartz latite

0.06

0.67

0.14

0.17

0.01

0.13

0.02

0.03

0.005

0.03

< 0.005

0.006

0.009

0.19

0.04

0.04

< 0.005

0.03

0.006

< 0.005

0.02

0.17

0.04

0.03

< 0.005 0.01

0.04 0.16

0.009 0.03

0.008 0.02

< 0.005

0.02

< 0.005

< 0.005

0.01

0.17

0.03

0.02

_

-

-

Tertiary andesite

0.054

<0.004

0.074

0.087

<0.004

<0.004

0.043

<0.004

<0.001

<0.001

<0.001

0.018

0.011

<0.001

0.012

<0.001

<0.001

<0.001

<0.001

<0.001

<0.001

<0.001

<0.001

<0.001

0.020

O.001

0.026

O.001

0.026

0.044

0.033

0.039

<0.001

<0.001

<0.001

<0.001

<0.001

<0.001

<0.001

<0.001

O.001

O.001

<0.001

<0.001

<0.001

<0.001

0.023

<0.001

<0.001 <0.001

<0.001 0.027

<0.001 0.011

<0.001 0.030

<0.001 0.014

<0.001 <0.001

<0.001 <0.001

<0.001 <0.001

<0.001

<0.001

<0.001

<0.001

<0.001

<0.001

<0.001

<0.001

<0.001

<0.001

<0.001

0.014

<0.001

O.001

0.021

<0.001

<0.0

<0.0

<0.0

<0.0

<0.0

<0.0

<0.0

<0.0
Tertiary sedimentary rock

0.138 0.028

0.153 0.027

0.064 <0.001

0.082 0.022

0.040 0.016

0.083 0.016

0.059 <0.001

0.153

0.071

0.025

<0.001

0.030

0.015

0.048

0.054

0.088

<0.001

<0.001

0.037

<0.001

0.025

0.041

0.019

O.001

O.001

O.001

O.001

O.001

0.040 0.027

0.024 0.018

0.032 O.001

O.001 O.001

O.001 O.001

0.025 O.001

0.025 O.001

0.038

O.001

0.013

O.001

0.011

0.021

0.016

0.026

0.018

O.001

O.001

O.001

O.001

O.001

0.045

0.026

O.001

0.023

O.001

O.001

0.017

0.03

0.02

O.00

O.00

O.00

O.00

O.00

Cretaceous Mesaverde Formation

0.047 <0.001

<0.004 <0.001

O.004 <0.001

0.044 <0.001

<0.004 <0.001

<0.004 <0.001

0.058 <0.001

0.145 0.013

<0.001

<0.001

0.010

<0.001

0.012

<0.001

<0.001

<0.001

0.014

<0.001

<0.001

0.021

0.021

0.022

0.029

0.016

O.001

O.001

O.001

O.001

<0.001

O.001

O.001

O.001

0.001 O.001

0.020 O.001

O.001 O.001

O.001 O.001

O.001 O.001

O.001 O.001

O.001 O.001

0.020 O.001

O.001

O.001

O.001

O.001

O.001

O.001

O.001

O.001

O.001

O.001

O.001

O.001

O.001

O.001

O.001

O.001

O.001

O.001

O.001

O.001

O.001

0.001

O.001

O.001

O.00

O.00

O.00

0.00

0.00

0.00

0.00

O.00

0.055 O.001

<0.004 <0.001

0.063 0.025

<0.004 <0.001

0.042 <0.001

<0.004 <0.001

<0.004 0.012

<0.004 0.012

0.063 <0.001

0.081 0.001

<0.001

<0.001

<0.001

<0.001

<0.001

<0.001

<0.001

<0.001

<0.001

<0.001

0.014

0.001

0.001

O.001

O.001

0.014

0.034

O.001

0.015

0.021

O.001

O.001

O.001

O.001

O.001

O.001

O.001

O.001

O.001

O.001

Cretaceous

0.001 0.001

0.001 O.001

O.001 O.001

0.001 O.001

0.001 O.001

0.001 O.001

O.001 O.001

O.001 O.001

O.001 O.001

0.011 O.001

Mancos Shale

O.001

O.001

O.001

O.001

O.001

O.001

0.001

O.001

O.001

O.001

O.001

O.001

O.001

O.001

O.001

O.001

O.001

O.001

O.001

O.001

0.021

O.001

O.001

O.001

O.001

0.014

O.001

O.001

O.001

O.001

0.00

O.00

O.00

O.00

O.00

O.00

O.00

O.00

O.00

O.00
o 

o

Mesozoic sedmentary rock

0.052

<0.004

O.004

<0.004

0.072

<0.001

<0.001

<0.001

<0.001

0.023

0.142

0.109

0.258

0.116

0.110

0.013

0.025

<0.001

0.031

0.032

<0.001

<0.001

<0.001

<0.001

<0.001

<0.001 <0.001 0.011

<0.001 <0.001 <0.001

<0.001 <0.001 <0.001

<0.001 <0.001 <0.001

0.010 <0.001 <0.001

<0.001

O.001

<0.001

<0.001

O.001

<0.001

<0.001

<0.001

<0.001

0.031

<0.0

<0.0

<0.0

<0.0

<0.0

<0.01

<0.01

<0.01

0.02

0.02

0.02

0.01

<0.01

<0.01

<0.01

0.01

<0.01

0.01

0.01

<0.01

<0.01

<0.01

<0.01

0.01

<0.01

<0.01

<0.01

<0.01

<0.01

<0.01

<0.01

<0.01

<0.01

<0.01

<0.01

0.007

0.005

0.008

0.01

0.02

0.02

< 0.005

< 0.005

< 0.005

< 0.005

0.01

0.006

0.007

0.009

0.008

< 0.005

< 0.005

0.005

0.006

< 0.005

< 0.005

< 0.005

< 0.005

< 0.005

< 0.005

< 0.005

< 0.005

< 0.005

< 0.005

< 0.005

< 0.005

< 0.005

< 0.005

< 0.005

< 0.005

< 0.005

< 0.005

< 0.005

< 0.005

< 0.005

< 0.005

< 0.005

< 0.005

< 0.005

< 0.005

Paleozoic sedimentary

0.006 < 0.005 < 0.005

< 0.005 < 0.005 < 0.005

< 0.005 < 0.005 < 0.005

0.01 < 0.005 < 0.005

< 0.005 < 0.005 < 0.005

< 0.005 < 0.005 < 0.005

< 0.005 < 0.005 < 0.005

< 0.005 < 0.005 < 0.005

< 0.005 < 0.005 < 0.005

< 0.005 < 0.005 < 0.005

< 0.005 < 0.005 < 0.005

< 0.005 < 0.005 < 0.005

0.005 < 0.005 < 0.005

< 0.005 < 0.005 < 0.005

< 0.005 < 0.005 < 0.005

rock

< 0.005

< 0.005

< 0.005

< 0.005

< 0.005

< 0.005

< 0.005

< 0.005

< 0.005

< 0.005

< 0.005

< 0.005

< 0.005

< 0.005

< 0.005

< 0.005

< 0.005

< 0.005

0.01

< 0.005

< 0.005

< 0.005

< 0.005

< 0.005

< 0.005

< 0.005

0.006

< 0.005

< 0.005

< 0.005

_

-

-

-

-

-

-

-

-

-

0.658

0.163

0.043

0.236

0.209

0.332

<0.004

<0.004

0.170

0.011

<0.001

0.087

0.027

0.081

0.029

-0.001

0.029

0.014

O.001

O.001

0.015

O.001

0.015

<0.001

0.186

0.026

<0.001

0.101

0.081

0.127

0.037

0.026

0.018

<0.001

<0.001

<0.001

<0.001

<0.001

0.001

<0.001

Tertiary and Proterozoic

0.170 0.031 0.098

0.027 <0.001 0.027

<0.001 O.001 0.012

0.072 0.015 0.027

0.059 O.001 0.035

0.088 0.014 0.054

<0.001 0.011 0.021

<0.001 O.001 0.014

rock

O.001

<0.001

O.001

<0.001

<0.001

O.001

O.001

<0.001

0.087

0.017

<0.001

0.015

0.027

0.027

<0.001

<0.001

0.01

<0.00

<0.00

<0.00

<0.00

0.01

0.01

0.01
Tl Pb Bi Th U

|ig/L |ig/L |ig/L |ig/L (ig/L

Tertiary basalt

<0.005

<0.005

<0.005

<0.005

<0.1 <0.005 0.069

1.42 O.005 0.100

<0.1 <0.005 0.092

<0.1 <0.005 0.073

0.15

0.07

0.06

0.04

Tertiary ash flow tuff

0.054

0.059

<0.005

<0.005

<0.005

<0.1 <0.005 0.567

1.10 O.005 0.501

<0.1 <0.005 0.072

<0.1 <0.005 0.097

<0.1 <0.005 0.130

0.19

0.20

0.06

0.02

0.01

Tertiary quartz latite

_

-

< 0.05 < 0.005 0.007

0.06 0.007 0.15

< 0.05 < 0.005 0.04

< 0.05 < 0.005 0.02

0.08

0.32

0.17

0.09

Tertiary andesite

<0.005

<0.005

<0.005

<0.005

<0.005

<0.005

<0.005

<0.005

<0.1 <0.005 0.297

<0.1 O.005 0.365

<0.1 <0.005 0.280

<0.1 <0.005 0.160

<0.1 <0.005 0.176

<0.1 <0.005 0.124

<0.1 <0.005 0.122

<0.1 <0.005 0.172

<0.001

0.10

0.28

0.19

0.24

0.13

0.20

0.23
o

K)

Tertiary sedimentary rock

0.062

<0.005

<0.005

<0.005

<0.005

<0.005

<0.005

<0.1 1.028

1.19 <0.005

2.87 <0.005

<0.1 <0.005

<0.1 <0.005

<0.1 <0.005

<0.1 <0.005

1.517

0.841

0.301

0.225

0.248

0.204

0.183

2.29

8.84

1.22

0.95

1.70

0.39

0.68

<0.005

<0.005

<0.005

<0.005

<0.005

<0.005

<0.005

0.054

Cretaceous Mesaverde

<0.1 <0.005

<0.1 <0.005

<0.1 <0.005

<0.1 <0.005

<0.1 <0.005

<0.1 <0.005

<0.1 <0.005

<0.1 <0.005

Formation

0.0015

0.023

0.0015

0.0015

0.0015

0.0015

0.0015

0.021

0.09

0.27

0.51

0.08

0.12

0.08

0.09

0.13

<0.005

<0.005

O.005

<0.005

<0.005

<0.005

0.055

<0.005

<0.005

<0.005

Cretaceous Mancos

<0.1 <0.005

<0.1 <0.005

<0.1 <0.005

<0.1 <0.005

<0.1 <0.005

<0.1 <0.005

<0.1 <0.005

<0.1 <0.005

<0.1 <0.005

<0.1 <0.005

Shale

0.040

0.041

0.037

0.031

0.062

0.020

0.049

0.021

0.022

0.022

0.35

0.58

0.45

0.22

0.12

0.27

0.14

0.34

0.52

0.12
Mesozoic sedimentary rock

<0.005

<0.005

<0.005

<0.005

<0.005

<0.1

1.66

<0.1

<0.1

<0.1

<0.005

<0.005

<0.005

<0.005

<0.005

0.094

0.077

0.065

0.079

0.045

1.43

2.33

5.78

2.12

3.70

Paleozoic sedimentary rock

_

-

-

-

-

-

-

-

-

-

-

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

0.005

< 0.005

< 0.005

< 0.005

< 0.005

< 0.005

< 0.005

< 0.005

< 0.005

< 0.005

< 0.005

< 0.005

< 0.005

< 0.005

< 0.005

0.02

0.007

0.006

< 0.005

0.005

< 0.005

0.006

0.006

0.01

0.01

0.005

0.005

0.008

0.006

< 0.005

0.84

1.22

0.69

0.13

0.26

0.49

1.08

0.76

0.54

0.70

0.28

0.70

0.74

0.61

0.48

<0.005

O.005

<0.005

<0.005

O.005

<0.005

0.052

0.068

Tertiary

1.31

1.07

<0.1

<0.1

1.02

<0.1

<0.1

<0.1

and Proterozoic rock

<0.005

O.005

<0.005

<0.005

<0.005

<0.005

<0.005

<0.005

0.079

0.046

0.023

0.033

0.071

0.050

0.375

0.333

7.27

0.62

0.59

0.17

0.98

1.36

0.37

0.63
Appendix 2. Chemical analyses of 19 stream waters from watersheds underlain by the Sunshine Peak Tuff, Lake 

Redcloud Peak area.

Site

RW02

RW10

RW11

RW12

RW14

RW15

RW16

RW17

RW21

RW22

RW23

RW24

RW25

RW26

RW27

RW30

RW31

RW32

RW33

Latitude 

Deg Min

37

37

37

37

37

37

37

38

37

37

37

37

37

37

37

37

37

37

37

58

56

56

56

56

56

56

0

54

54

54

54

55

56

54

58

58

57

57

Sec

59

40

37

54

56

46

28

12

29

26

24

44

5

9

20

22

24

53

19

Longitude 

Deg Min Sec

107

107

107

107

107

107

107

107

107

107

107

107

107

107

107

107

107

107

107

29

28

28

26

26

26

27

21

22

22

25

26

26

27

24

26

26

27

27

7

42

9

19

25

39

13

45

31

49

55

27

51

30

33

33

36

4

50

Type

Unnamed stream

Rock Creek

Cooper Creek

So. Fk. Silver Creek

Unnamed stream

Unnamed stream

Unnamed stream

Alpine Gulch

Unnamed stream

Bent Creek

Unnamed stream

Unnamed stream

Unnamed stream

Silver Creek

Unnamed stream

Unnamed stream

Upper Cooper Creek

Unnamed stream

Unnamed stream

Flow

15 gal/sec

5 gal/sec

10 gal/sec

20 gal/sec

1 gal/sec

1 qt/sec

3 qt/sec

18 gal/sec

low

mod

low

low

low

mod

low

low

low

low

low

Co

no p

Slig

Al oxide c

Al oxide c

Abundant rec

Slight 

Slight 

Slightly mu
PH

7.09

6.73

5.17

4.92

3.58

6.08

4.177

6.917

7.42

7.6

7.57

6.06

7.05

4.42

6.4

3.9

6.6

Cond 

pS/cm

110

117

117

127

320

70

148

128

93

94

121

210

87

129

44

140

55

194

47

Ca 

mg/l

15

14

12

12

22

7.8

11

15

12

12

18

33

11

14

6.3

12

7.6

14

6.7

Mg 

mg/l

1.7

2.5

1.52

4.5

1.22

2.4

1.4

1.4

1.62

1.2

2.4

0.5

1.4

0.7

2.3

0.7

Na

mg/l

0.7

0.41

0.6

2.2

0.6

0.52

1.2

1.2

2.3

4.4

1.1

1.1

0.9

1.2

0.4

1.1

0.4

K

mg/l

0.5

0.9

1.2

1.9

4.5

1.7

3.6

0.9

0.7

0.7

0.3

1.21

1.7

0.5

1.2

0.4

2.3

0.5

SiO2 

mg/l 36

109

29

16

25

1066788

106

103

174

Alkalinity 

mg/l

29

12

15

0.1

0.1

13

0.1

18

29

15

45

94

13

0.1

23

0.1

15

0.1

20

SO4 

mg/l

32

42

45

49

106

23

53

43

23

23

16

24

24

50

6.9

52

13

74

10

Cl 

mg/l

0.15

0.07

0.07

0.15

0.14

0.14

0.15

0.1

0.13

0.11

0.15

0.17

0.11

0.13

0.13

0.07

0.18

0.17

0.07

m

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0
o

ON

Mn 

mg/l

0.007

0.007

0.5

0.522

0.007

1.2

0.02

0.007

0.007

0.007

0.007

0.007

0.26

0.007

0.67

0.007

0.53

0.007

Fe 

mg/l

0.02

0.01

0.04

0.007

0.45

0.02

0.07

0.27

0.01

0.03

0.02

0.02

0.01

0.03

0.04

0.07

0.01

0.04

0.02

Cu 

M9/I

0.7

0.7143

0.73

0.7

0.7

0.7

0.7

0.7

0.73

0.72

0.76

0.7

Zn 

M9/I 27

90

110

280

10

83522222

1002

1302

932

Co 

M9/I

0.7

0.71

0.7

12

0.742

0.7

0.7

0.7

0.7

0.71

0.73

0.73

0.7

Ni

M9/I

0.7

0.7227

0.731

0.7

0.7

0.7

0.7

0.72

0.72

0.7

0.7

0.7

Mo 

M9/I 1

0.7

0.7

0.7

0.7

0.7

0.71

0.7

0.7691

0.72

0.7

0.7

0.7

0.7

As 

M9/I

0.7

0.7

0.7

0.7

0.7

0.7

0.7

0.7

0.7

0.7

0.7

0.7

0.7

0.7

0.7

0.7

0.71

0.7

U 

M9/I

0.1

0.07

2.6

6.6

3.4

0.2

3.5

0.07

0.3

0.2

2.1

8.1

0.1

2.6

0.6

5.2

0.07

4.6

0.07

Li 

M9/I 3335

162

8.7243

11

2124

4.73

0.7

5.7

0.7

B

M

0

0

1

2

6

0

4

0

0

0

0

0

0

2

0

3

0

0
Rb 

M9/I

1.5

4.1

3.6

6.8

21

6.2

18

1.9

1.9

1.8

1.2

2.4

2.1

6.6

1.84

0.8

9.5

1.1

Sr 

M9/I

120

55

54

39

56

29

35

160

140

140

190

320

38

110

39

49

42

44

79

Y

M9/I

0.07

0.07

8.8

9.2

9.2

0.2

3.5

0.07

0.07

0.07

0.07

0.07

0.074

0.1

13

0.07

13

0.07

Cs 

M9/I

0.2

0.15

0.15

0.15

1.8

0.15

2.5

0.15

0.15

0.15

0.2

0.4

0.15

0.2

0.7

0.15

0.15

1.1

0.2

Ba 

M9/I

3.4

4.9

14

8.9

6.5

7.5

26

18

4.3

4.1

2.4

32

5.1

14

0.9

14

13

7.2

14

La 

M9/I

66

0.27

5.8

2.9

0.21

0.2

0.07

0.07

0.1

0.07

0.2

2.2

0.07

9.8

0.2

4.1

0.07

Ce 

M9/I

0.07

0.07

14

10

6.7

0.07

2.1

0.07

0.07

0.07

0.07

0.07

0.1

3.5

0.1

21

0.07

13

0.1

Pr 

M9/I

0.07

0.07

2.2

1.71

0.07

0.4

0.07

0.07

0.07

0.07

0.07

0.07

0.6

0.07

2.8

0.072

0.07

Nd 

M9/I

0.07

0.07

8.7

5.8

4.7

0.1

1.6

0.07

0.07

0.07

0.07

0.07

0.1

2.4

0.07

10

0.29

0.07

Sm 

M9/I

0.07

0.07

1.8

1.4

1.2

0.07

0.3

0.07

0.07

0.07

0.07

0.07

0.07

0.5

0.07

2.2

0.07

2.1

0.07

Eu 

M9/I

0.07

0.07

0.2

0.2

0.2

0.07

0.07

0.07

0.07

0.07

0.07

0.07

0.07

0.07

0.07

0.2

0.07

' 0.3

0.07