Substrate Geochemistry and Soil Development 

in Boreal Forest and Tundra Ecosystems in the 

Yukon–Tanana Upland and Seward Peninsula, 

Alaska 

U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2008–5010
Cover. View of the middle reaches of the Tibbs Creek drainage in the Big Delta B-1 quadrangle, looking west-northwest. 

Soils in this area of the Yukon-Tanana Upland are mainly Inceptisols that lack permafrost, contain Quaternary loess, and 

are derived from the weathering of Paleozoic metamorphic and Early Cretaceous granitic rocks. (Photograph by L.P. Gough, 

U.S. Geological Survey)
Substrate Geochemistry and Soil 

Development in Boreal Forest and Tundra 

Ecosystems in the Yukon–Tanana Upland 

and Seward Peninsula, Alaska 

By L.P. Gough, J.G. Crock, B. Wang, W.C. Day, D.D. Eberl, R.F. Sanzolone, and 

P.J. Lamothe 

Scientific Investigations Report 2008–5010

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

DIRK KEMPTHORNE, Secretary

U.S. Geological Survey

Mark D. Myers, Director

U.S. Geological Survey, Reston, Virginia: 2008

For product and ordering information:

World Wide Web: http://www.usgs.gov/pubprod

Telephone: 1-888-ASK-USGS

For more information on the USGS—the Federal source for science about the Earth, its natural and living resources, 

natural hazards, and the environment:

World Wide Web: http://www.usgs.gov

Telephone: 1-888-ASK-USGS

Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the 

U.S. Government.

Although this report is in the public domain, permission must be secured from the individual copyright owners to 

reproduce any copyrighted materials contained within this report.

Suggested citation:

Gough, L.P., Crock, J.G., Wang, B., Day, W.C., Eberl, D.D., Sanzolone, R.F., and Lamothe, P.J., 2008, Substrate geochemistry and soil development in boreal forest and tundra ecosystems in the Yukon–Tanana Upland and Seward 

Peninsula, Alaska: U.S. Geological Survey Scientific Investigations Report 2008–5010, 18 p. 
iii

Contents

Abstract ..........................................................................................................................................................1

Objective..........................................................................................................................................................1

Introduction.....................................................................................................................................................2

Landscape Setting................................................................................................................................2

Soils.........................................................................................................................................................2

Geology...................................................................................................................................................4

Methods...........................................................................................................................................................5

Results and Discussion.................................................................................................................................5

Soil Weathering — Major Element Ratios........................................................................................5

Soil Weathering — Soil Bulk Mineralogy........................................................................................7

Chemistry of Soil Sequential Extraction Leachates......................................................................10

Soil Loess and Geochemical Signatures ........................................................................................14

Summary........................................................................................................................................................16

Acknowledgments.......................................................................................................................................16

References Cited..........................................................................................................................................16

Figures

1. Index map showing the location of the soil sampling areas in the Yukon-Tanana 

Upland (YTU) and the Seward Peninsula (SP), Alaska...........................................................3

2. Photograph showing typical well-drained boreal forest Inceptisol developed 

over granite....................................................................................................................................4

3A. Box plots showing the ratios of K2O/TiO2, CaO/TiO2, and Fe2O3/TiO2 from soils 

(three horizons) developed over two generalized rock types in boreal forest 

and tundra ecosystems ...............................................................................................................6

3B. Box plots showing the ratios of Cd/Ti and Zn/Ti from soils (three horizons) 

developed over two bedrock types in boreal forest and tundra ecosystems ....................7

4. Graphs showing simple regression between muscovite, total clay, and loss on 

ignition (organic matter) and the concentration of cadmium (Cd) and zinc (Zn) 

in soil samples from the Yukon-Tanana Upland and the Seward Peninsula, Alaska......11

5. Graphs showing results of the sequential extraction for cadmium and zinc of 

three soil horizons (A, B, and C) using seven different soil profiles and six 

extractants...................................................................................................................................12

6. Plots showing CaO versus MgO and Al2O3 versus Fe2O3 in three soil horizons 

segregated by bedrock type .....................................................................................................15
iv

Tables

1. Analytical methodology for parameters reported for soils, soil leachate, 

and rocks........................................................................................................................................5

2. Bulk mineralogy (quantitative XRD) and site characteristics for tundra soils 

developed from bedrock and loess, Yukon-Tanana Upland and Seward 

Peninsula, Alaska .........................................................................................................................8

3. Ratio of quartz to major soil minerals (calculated on a weight percent basis) in 

A, B, and C horizon soil samples from three sites in the Yukon-Tanana Upland 

(YTU) and three sites in the Seward Peninsula (SP)...............................................................9

4. Yukon-Tanana Upland soil samples used in the sequential extraction results 

shown in figure 5.........................................................................................................................13

5. Chemistry and targeted soil fraction of six (I-VI) sequential extractants of soil 

samples from the Yukon-Tanana Upland, Alaska..................................................................13

Multiply By To obtain

Length

centimeter (cm) 0.3937 inch (in.)

millimeter (mm) 0.03937 inch (in.)

meter (m) 3.281 foot (ft) 

kilometer (km) 0.6214 mile (mi)

Mass

gram (g) 0.03527 ounce, avoirdupois (oz)

kilogram (kg) 2.205 pound avoirdupois (lb)

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows:

°F=(1.8×°C)+32

Abbreviations used in this report

Ka - thousand years before present

M - molar

Ma - million years before present

mL - milliliter

μm - micrometer

n - number of samples

N - normal

NIST - National Institute of Standards and Technology

R2

 - square of the correlation coefficient

USGS - U.S. Geological Survey 

Conversion Factors and Abbreviations
Abstract 

We report on soil development as a function of bedrock 

type and the presence of loess in two high latitude ecosystems 

(boreal forest and tundra) and from two regions in Alaska—

the Yukon-Tanana Upland (YTU, east-central Alaska) and the 

Seward Peninsula (SP, far-west coastal Alaska). This approach 

to the study of “cold soils” is fundamental to the quantification 

of regional geochemical landscape patterns. Of the five state 

factors in this study, bedrock and biota (ecosystem; vegetation 

zone) vary whereas climate (within each area) and topography 

are controlled. The influence of time is assumed to be controlled, as these soils are thousands of years old (late Quaternary to Holocene). 

The primary minerals in soils from YTU, developed over 

loess and crystalline bedrock (metamorphic and intrusive), are 

quartz, plagioclase, and 2:1 clays; whereas in the SP, where 

loess and metasedimentary bedrock (schist and quartzite) 

predominate, they are quartz and muscovite. The A horizon of 

both regions is rich in peat. Examination of the ratio of mobile 

(K2

O, CaO, and Fe2O3) to immobile (TiO2) major oxides, 

within each region, shows that very little difference exists in 

the chemical weathering of soils developed between the two 

ecosystems examined. Differences were observed between 

tundra soils developed in the two regions. These differences 

are most probably due to the dissimilarity in the geochemical 

importance of both loess and bedrock. 

A minimal loss of cadmium with soil depth is seen for 

soils developed over YTU crystalline bedrock in the boreal 

forest environments. This trend is related to the mobility of 

cadmium in these soils as well as to its biogenic cycling. 

Major differences were observed in the proportion of cadmium 

and zinc among the A, B, and C horizon material sequestered 

in various soil fractions as measured by sequential soil extractions. These trends followed such variables as the decrease 

with depth in organic matter, the change in clay minerals, and 

the change in the proportion of oxides/hydroxides. An analysis 

of the bulk soil mineralogy and the relation between CaO and 

MgO and Al2

O3 and Fe2O3 indicates that the silty textured soils 

of the YTU are predominantly eolian (that is, of late Tertiary 

or Quaternary age) but not broad-regional in origin. Their 

composition instead is probably the result of locally derived 

dusts as well as input from long-term, in-place bedrock weathering. 

Objective

The objective of the study was to test two alternative 

hypotheses about high latitude soil weathering: (1) Soils developed from combined loess and uniform bedrock units have 

different geochemical signatures, depending on the ecosystem where they are formed, versus (2) soils developed where 

weathering rates are too slow, ecosystem processes are too 

indistinguishable, or the presence of loess material confounds 

meaningful differences in the soil geochemical signatures of 

ecosystems (or vegetation zones). The ecosystems investigated 

were the boreal forest and tundra (which included Arctic, open 

alpine, and shrub-tundra).

The following processes and (or) physical characteristics could influence geochemical signatures: (1) bedrock 

type, (2) age of soil, (3) physical, chemical, and biological 

weathering rates versus loess deposition rates (Muhs and 

others, 2004), (4) vegetative cover and organic acid illuviation, (5) aspect and altitude, and (6) depth to permafrost (and 

drainage efficiency). Through site selection within each region 

we controlled as many of these variables as possible while 

varying the bedrock and biota (ecosystem). We realize, however, that some local climatic differences were evident owing 

to the presence or absence of permafrost and to dissimilarities observed in the depth, thickness, and characteristic of the 

weathering profiles.

Substrate Geochemistry and Soil Development in 

Boreal Forest and Tundra Ecosystems in the 

Yukon–Tanana Upland and Seward Peninsula, Alaska 

By L.P. Gough, J.G. Crock, B. Wang, W.C. Day, D.D. Eberl, R.F. Sanzolone, and P.J. Lamothe 
2 Substrate Geochemistry and Soil Development in Boreal Forest and Tundra Ecosystems in Alaska

Introduction

Landscape Setting

Several processes affect the development of high latitude 

(cold) soils and their resultant regional landscape geochemical 

patterns. We focused on the development of soils over crystalline (metamorphic and intrusive) and metasedimentary (schist 

and quartzite) bedrock. If ecosystem differences result in soil 

development differences, then, over time, system perturbations 

(climate change) could alter regional geochemical landscape 

patterns. The study areas were the Yukon-Tanana Upland 

(YTU) located in the Big Delta B-1 and B-2 quadrangles 

about 200 kilometers (km) east-southeast of Fairbanks and 

the Seward Peninsula (SP), located in the Nome and Solomon 

quadrangles in far western Alaska.

The YTU study area (fig. 1) is characterized by rounded, 

low mountains with scattered sparsely vegetated to barren 

high peaks. Nowacki and others (2002) classify the area as 

the Intermontane Boreal Ecoregion. The boreal forest vegetation is composed of closed spruce-hardwood forest containing 

white and black spruce, paper birch, aspen, and balsam poplar. 

The tree line is at about 900 meters (m), and above it the 

alpine tundra zone is composed of low shrubs (willow, birch, 

blueberry, crowberry) and a ground cover of grasses, forbs, 

mosses, and lichens. Lightening-caused wildfires are common, and most of our study sites, especially those in forested 

areas, showed evidence of past fire disturbance. The climate 

of the area is typical of continental interior Alaska, which is 

characterized by warm, dry summers, very cold, dry winters, 

daylight hours that vary from about 4.5 hours in December to 

19.5 hours in June, and broad fluctuations in ambient temperature (Van Cleve and Yarie, 1986).

The SP landscape is treeless and rolling with vegetated 

arctic tundra dominated by shrubs (willow, blueberry, crowberry), herbs, grasses, forbs, lichens, and mosses. The region 

sampled is characterized by a much lower elevation than 

YTU (maximum of about 400 m) and possesses short cool, 

wet summers and cold, dry winters. Soils of this region are 

less influenced by loess than in the YTU (Muhs and others, 

2003a). Nowacki and others (2002) classify this area as the 

Bering Tundra Ecoregion. The latitude (64° N.) is the same for 

both SP and YTU (fig. 1).

Soils

The factors that control soil formation (climate, biota, 

parent material, topography, and time) (Jenny, 1980) are the 

same factors that have been used by Van Cleve and others 

(1991) to model the structure and function of the boreal forest 

biome in Alaska. Except for permafrost areas (Ferrians, 1965), 

these soils are ice free for only a few months during the summer, and uppermost horizon temperatures seldom exceed 5° to 

10° C. Both chemically and biologically mediated weathering 

are slow (Campbell and Claridge, 1992). Boreal forest and 

tundra vegetation produce organic acids, through organic matter decomposition, that accelerate certain soil formation processes (for example, the release of metal cations from silicate 

minerals and their co-precipitation with Al, Fe, and Mn oxides 

and hydroxides). An even colder environment, with slower 

soil microbial activity and less vegetative cover, occurs at 

higher elevations and latitudes. In these environments the soils 

usually have fewer organic acids and consequently have even 

slower soil formation processes. The principal proton donor in 

these systems is carbonic acid, the product of root respiration 

(Campbell and Claridge, 1992), which becomes even more 

soluble in water as temperatures decrease.

The study area soils are late Quaternary to Holocene in 

age (Muhs and others, 2003b) and developed from both loess 

and a wide variety of predominantly crystalline and metasedimentary bedrock types (see Geology section below). Soils 

collected were either Inceptisols (mainly Cryepts or Gelepts) 

(fig. 2) or Gelisols (mainly Orthels). Spodosols were observed 

but not collected. These latter soils have abundant organic carbon within the spodic horizon and were usually found only in 

well-drained areas in white spruce forests. Greater than 30 percent of our sites were near saturation at the time of collection, 

and permafrost, when present, was commonly observed from 

15 to 50 centimeters (cm) below the surface. Our soils can be 

described broadly as those with and those without permafrost 

or evidence of permafrost. Those with permafrost were most 

commonly in areas of tundra overlain with a thick O horizon. 

The O horizon was composed of cryptogams and abundant 

plant debris that became more sapric with depth and overlaid 

the silty loam to fine sandy loam mineralized A1 soil horizon. 

The A horizon was usually <10 cm in thickness and dark 

brown in color (indicative of abundant organic matter), with 

numerous roots, and a few possessed an eluviation (E) horizon 

(fig. 2). The typical B horizon was usually about as thick as 

the A horizon, lighter and more reddish in color, and contained 

moderate root volume. Yellowish C-horizon soils commonly 

extended below 20 to 40 cm in depth and consisted of silt and 

fine-to-coarse sand with small blocks of angular bedrock and 

few roots.

Although boreal and tundra areas differ greatly in the 

degree of cryoturbation, snow accumulation depths, and 

vegetative composition, we attempted to maintain consistency 

within the two major areas sampled (YTU and SP). This consistency resulted in fairly uniform soil horizontal characteristics. What did vary among the sites, however, was the abundance of loess, the presence and amount of bedrock inclusions, 

and the ranges in soil moisture.
Introduction 3

Figure 1. Location of the soil sampling areas in the Yukon-Tanana Upland (YTU) and the Seward 

Peninsula (SP), Alaska.

0

0

100 200 MILES

200 400 KILOMETERS

144° 162°

70°

66°

62°

58°

Barrow

Nome Fairbanks

RUSSIA

CANADA

UNITED STATES

UNITED STATES

Seward

Peninsula

 ( S P )

YukonTanana

Upland

(YTU)

Anchorage

ARCTIC

PACIFIC OCEAN

BERING SEA

K u s k o k w i m

R i v e r

K o b u k R i v e r

K o y u k u k R i v e r

Y u

k o n

R i v e r

OCEAN

Areas of soil collection reported in this study.
4 Substrate Geochemistry and Soil Development in Boreal Forest and Tundra Ecosystems in Alaska

Geology

The oldest geologic units within YTU are composed of a 

series of biotite-sillimanite gneiss, quartzofeldspathic biotite 

gneiss, and a sequence of metagraywacke that is locally interlayered with quartzite and metapelite. The protoliths for these 

metasedimentary units included epiclastic to pelitic sediments. 

The region experienced two major episodes of plutonism, one 

during the Devonian (~365 million years before present, Ma) 

and another during the Cretaceous (~104–113 Ma). In addition 

to soils developed over the metasediments, some of the soils 

we collected in YTU were developed over the plutonic/intrusive rocks and included the Goodpaster granite, the Swede 

Peak granite, granodioritic dikes, and various granodioritic 

to granite stocks. For a thorough discussion of the geologic 

setting, deformational history, and age of mineralization for 

the YTU area, see Wilson and others (1985), Dusel-Bacon and 

Hansen (1992), Dusel-Bacon and others (2002), Dilworth and 

others (2002), Selby and others (2002), Day and others (2003), 

and Day and O’Neill (in press). 

Like the YTU, the Seward Peninsula (SP) study area 

(fig. 1) is predominantly a crystalline terrane. Our sites were 

located exclusively over metasedimentary bedrock of the 

Nome Group (Proterozoic to Paleozoic age) that has been 

subjected to blueschist-facies metamorphism (Werdon and 

others, 2005). Unlike YTU, however, the Nome Group rocks 

are composed of interlayered metasedimentary and igneous 

rocks, including chlorite-rich schist, mafic granofels, marble, 

impure marble quartzite, and metagraywacke (Bundtzen and 

others, 1994; Till and others, 1986; Till and Dumoulin, 1994; 

Werdon and others, 2005). The soils developed over the Nome 

Group rocks are of particular interest, as the schist can contain 

as much as 5 percent graphite and the quartzite 2 to 10 percent 

(Werdon and others, 2005). It is suspected that bedrock areas 

with high graphite content could also be high in total cadmium 

(John F. Slack, U.S. Geological Survey, personal commun., 

2004). In previous work, we became curious about the mobility and bioavailability of cadmium in these soils (Gough and 

others, 2001) and its bioaccumulation by willow (Gough and 

others, 2002).

Figure 2. Typical well-drained boreal forest Inceptisol developed over granite. The A horizon, held together by numerous plant 

roots, is overturned in this photograph to show its dark-brown color and the presence of a weak, ash-colored E horizon.

C horizon

B horizon A horizon

E horizon

numerous

roots
Results and Discussion 5

Methods

Soil samples were collected over crystalline (metamorphic and intrusive) bedrock between 1999 and 2005 from 

throughout the Big Delta B-1 and B-2 quadrangles of the YTU 

(Gough and others, 2005). In 2004 and 2005 we collected soils 

developed over metasediments (schist and quartzite) on the 

SP. An effort was always made to collect mature, residual soils 

whenever possible. The presence of loess in the YTU soils 

was ubiquitous but variable; in SP soils the presence of loess 

was ubiquitous and uniformly less in volume than in the YTU 

soils. Sites were located well above contemporary flood levels 

on slopes that did not exceed a 15 percent grade. Cryoturbated 

soils were observed but these sites were purposely avoided; 

most commonly they were demonstrated by the mixing of soil 

horizon boundaries and by the presence of frost boils at the 

surface. 

Soil study sites were selected on the basis of the following landscape and soil criteria: (1) soils developed over 

known lithologic units were targeted, (2) peaty soils were 

avoided, (3) permafrost where present was at a depth >30 cm, 

and (4) soils were mature, having recognizable soil-horizon 

development. Sites were also selected on the basis of the following ecosystem criteria: (1) sites were in boreal forests and 

in open tundra or shrub-tundra, (2) sites were selected that had 

not been recently burned (within the past 30–50 years based 

on tree-ring examination), and (3) sites were as well drained 

as possible for the area (usually with a southerly or ridge 

crest exposure). Commonly the sites were well drained if they 

lacked permafrost. 

At least one soil pit was dug at each study site. Where 

available, samples of A1, B, and C soil horizon material 

(about 1 kilogram (kg) of each) were collected using a spade, 

mixed separately using a plastic spatula and bucket, placed 

in paper U.S. Geological Survey (USGS) soil sample bags, 

and stored at room temperature. In the laboratory the soils 

were dried (ambient temperature, forced air), mechanically 

disaggregated, and sieved to pass 10 mesh (2 millimeters, 

mm), and the <10-mesh material was further ground to pass a 

100-mesh sieve (150 micrometers, μm). The ground material 

was digested and subjected to chemical analyses to determine 

elemental content (table 1).

extraction solution for each of six treatments (fractions). A 

modification of the methods of Hall and others (1996a; 1996b) 

and Chao (1984) was used as follows: Fraction I—(1 molar 

(M) sodium acetate), target: easily exchangeable and carbonate-sorbed mineral phases. Fraction II—(0.1M sodium phosphate brought to pH 10 using nitric acid), target: labile component associated with organic matter. Fraction III—(0.25 M

hydroxylamine hydrochloride in 0.25 normal (N) HCl), 

target: amorphous Fe- and Mn-oxides. Fraction IV—(1 M

hydroxylamine hydrochloride in 25 percent acetic acid), 

target: crystalline Fe-, Mn-, and Al-oxides, secondary sulfides, monosulfides, plus the edges of some silicate minerals. 

Fraction V—(1 g potassium chlorate and 10 mL HCl), target: 

sulfide minerals. Fraction VI—(four-acid “total” dissolution 

of residue (HF, HCl, HClO4 and HNO3)), target: silicate and 

some resistate minerals. 

Quantitative bulk soil mineralogy was determined by 

powder X-ray diffraction analysis for a selected subset of 

unground samples of the A, B, and C horizon soils from both 

study areas. For details of this method, using the RockJock 

computer program coupled with a Cu-Kα radiation diffractometer, see Eberl (2003; 2004). 

Table 1 lists the laboratory methodologies used in 

the analysis of rocks, soils, and soil leachate samples. The 

complete geochemistry of area bedrock associated with the 

YTU soils is found in Gough and others (2005) and in Day 

and O'Neill (in press). Details of the quality assurance-quality 

control protocols of the Denver laboratories of the USGS are 

given in Crock and others (1999) and Taggart (2002). These 

methods incorporate the periodic analysis of blanks, laboratory-made duplicates, and several USGS and National Institute of Standards and Technology (NIST) standard reference 

materials for quality control purposes.

Results and Discussion

Soil Weathering — Major Element Ratios

Muhs and others (2004) used selected major element 

ratios (mobile-to-immobile elements) as a proxy for examining mineral depletions due to chemical weathering in soils 

from south-central Alaska. They examined CaO/TiO2 (plagioclase and hornblende), K2

O/TiO2 (mica and potassium 

feldspar), and Fe2O3/TiO2 (“podzolization,” or downward 

migration of organic matter, Fe, and Al), reasoning that a loss 

of these mobile oxides in surface soil horizons could demonstrate weathering. Figure 3A shows the percentile box plots 

for the ratio of these major oxides in A, B, and C horizon 

soils. The plots are segregated by ecosystem (soils developed 

in boreal forests and tundra) and by bedrock type (crystalline: 

metamorphic and intrusive (YTU), and metasediments: schist 

and quartzite (SP)). Of the 52 soil profiles that these data 

represent, 45 were developed over metamorphic and intrusive 

bedrock (YTU) and 7 were over schist and quartzite (SP). Two 

of the soil profiles from YTU lacked a recognizable B horizon. 

Table 1. Analytical methodology for parameters reported for 

soils, soil leachate, and rocks. The methods follow those detailed 

in Crock and others (1999), Taggart (2002), and Eberl (2003; 2004). 

Parameter Method

Element concentrations Inductively coupled plasma-mass 

spectrometry (ICP-MS)

Ash yield of soil Gravimetric

Quantitative bulk mineralogy 

of soil

Powder X-ray diffraction using 

RockJock computer program 

(Eberl, 2003) 

Sequential partial extraction of soils used 1 gram (g) of 

bulk soil material sieved to <2 mm and 25 milliliters (mL) of 
6 Substrate Geochemistry and Soil Development in Boreal Forest and Tundra Ecosystems in Alaska

Figure 3A. Box plots of the ratios of K2O/TiO2, CaO/TiO2, and Fe2O3/TiO2 from soils (three horizons) 

developed over two generalized rock types in boreal forest and tundra ecosystems. Soils 

developed over crystalline rocks are from the Yukon-Tanana Upland, whereas soils developed over 

metasediments are from the Seward Peninsula, Alaska (table 2). 

Crystalline (n=45),

Yukon-Tanana Upland

Metasediment (n=7),

Seward Peninsula

EXPLANATION

Generalized rock type >90th

90th

75th

25th

10th

<10th

Median

(Percentiles)

A horizon A horizon

B horizon

C horizon

B horizon

C horizon

A horizon

B horizon

C horizon

1

10

100

0.1

1

10

100

1

10

100

0.1

1

10

100

1

10

100

0.1

1

10

100

K2O/TiO2 K2O/TiO2 K2O/TiO2CaO/TiO2 CaO/TiO2 CaO/TiO2

ECOSYSTEM ECOSYSTEM ECOSYSTEM

1

10

100

Fe2O3/TiO2 Fe2O3/TiO2 Fe2O3/TiO2 1

10

100

1

10

100

A

Boreal forest Tundra Boreal forest Tundra Boreal forest Tundra
Results and Discussion 7

Figure 3B. Box plots of the ratios of Cd/Ti and Zn/Ti from soils 

(three horizons) developed over two bedrock types in boreal forest 

and tundra ecosystems. Soils developed over crystalline rocks 

are from the Yukon-Tanana Upland, whereas soils developed over 

metasedimentary rocks are from the Seward Peninsula, Alaska 

(table 2).

The ratios for K2O/TiO2 and Fe2O3/TiO2 are generally greater, 

however, in soils developed over SP schist and quartzite compared to soils from YTU. In addition, the ratios for K2

O/TiO2

and possibly Fe2O3/TiO2 show a slight loss in the A horizon, 

compared to samples at greater depth (especially for soils over 

schist and quartzite). This could be interpreted as demonstrating the downward migration of these oxides in soils over this 

bedrock type. As stated above, we do not have control over 

time (of soil development) and this presents some uncertainty 

to the comparison of geochemical signatures. 

Figure 3B presents plots for total cadmium (Cd) and 

zinc (Zn) normalized to total titanium (Ti) in the A, B, and 

C horizon of soils developed in the same two ecosystems as 

above. Although, in general, the geochemistry of Cd and Zn 

in soils is similar, Cd and Zn behave differently in the soils of 

this study. Some loss in Cd with depth is seen for YTU soils 

in the boreal forest environment. Little change in Cd is noted 

with depth in the tundra soils. Zinc shows little or no change 

with depth among bedrock types or among ecosystems. The 

trends for Cd are related in part to the biogenic cycling of Cd 

(Gough and others, 2001; Gough and others, 2002) and its 

probable association with organic matter (McArthur and others, 2001). Cadmium is bioavailable in this environment and is 

being absorbed by plants, taken up into leaf tissue (especially 

willows), and then redeposited on the soil surface through 

leaf drop. Zinc does not demonstrate this type of biogenically 

mediated enrichment.

Soil Weathering — Soil Bulk Mineralogy

The degree of chemical weathering of these soils can also 

be examined through the analysis of the relative abundance of 

primary and secondary minerals among soil horizons. Nine 

soil samples (three sites each with three horizons) in both 

YTU and SP were examined quantitatively for their bulk mineralogy using powder X-ray diffraction (table 2). 

There are major differences in the non-clay mineralogy of the soils from the two study areas with quartz as the 

most abundant non-clay mineral followed by peat (“mineral” 

peat as defined by X-ray diffraction) > plagioclase feldspar 

> goethite (table 2). These four primary minerals make up 

~60 weight percent of the bulk mineralogy in the YTU soils 

and ~50 weight percent in the SP soils. Both quartz and peat 

are about twice as abundant in the YTU soils, compared to 

the SP soils. Table 2 shows the dramatic and rapid decrease 

in peat with soil depth in the YTU soils; this pattern is not 

so pronounced in the Arctic tundra SP soils. The quantitative 

analysis of peat by X-ray diffraction correlates positively with 

total organic matter (as measured by loss on ignition) in a 

nearly1:1 relation (R2

 >0.96) for both area populations. Even 

after factoring out the influence of the dominant presence of 

quartz, a decreasing pattern of peat with depth is still not as 

dramatic for the SP soils (table 3). 

If one assumes that time is nearly the same for the development of these soils, figure 3A shows that very little difference exists, between the two ecosystems tested, in the median 

or variance for ratios of CaO/TiO2

, K2O/TiO2, or Fe2O3/TiO2. 

Crystalline (n=45),

Yukon-Tanana Upland

Metasediment (n=7),

Seward Peninsula

EXPLANATION

Generalized rock type >90th

90th

75th

25th

10th

<10th

Median

(Percentiles)

ECOSYSTEM ECOSYSTEM

Cd/Ti Cd/Ti Cd/Ti

Zn/Ti Zn/Ti Zn/Ti

A horizon A horizon

B horizon

C horizon

B horizon

C horizon

B

0.01

0.1

1

10

100

10

100

1,000

10,000

100,000

0.01

0.1

1

10

100

10

100

1,000

10,000

100,000

0.01

0.1

1

10

100

10

100

1,000

10,000

100,000

Boreal

forest

Boreal

forest

Tundra Tundra 
8 Substrate Geochemistry and Soil Development in Boreal Forest and Tundra Ecosystems in Alaska Table 2. Bulk mineralogy (quantitative XRD) and site characteristics for tundra soils developed from bedrock and loess, Yukon-Tanana Upland and Seward Peninsula, Alaska. [Crystalline (metamorphic and intrusive, YTU): Kgmh, Mount Harper granodiorite; Dag, Devonian augen gneiss; Metasediment (SP): 

O

sq, Ordovician to Precambrian mixed unit of the Nome Group 

(graphitic schist and quartzite); 

O

t, Precambrian mixed unit of the Nome Group (chlorite-rich schist and marble); --, mineral was not observed. Geologic units based on Werdon and others (2005)]

Sample 

identification Soil horizon Site elevation (meters) Rock unit

Weight Percent

Loss on 

ignition Quartz Potassium feldspar Plagio- clase Calcite Dolo- mite Amphi- bole Pyrite Goethite Apatite Rutile Peat Total non- clay 2:1 clay Chlorite Musco- vite Total clay

Yukon-Tanana Upland (YTU)

05AK33A

A 1,150 Kgmh 21 20 4.1 15 -- -- 0.2 -- 0.3 0.2 -- 24 64 16 9.4 11 36

05AK33B

B 13 24 5.7 17 -- -- -- 0.1 .4 -- 0.2 14 62 15 13 11 38

05AK33C

C 8.0 32 6.2 18 -- -- .5 -- .5 .2 -- 8.3 66 16 11 6.9 34

05AK35A

A 1,200 Kgmh 56 5.3 .7 3.9 -- -- -- -- .7 -- -- 63 73 13 4.3 9.5 27

05AK35B

B 13 27 7.6 21 -- -- -- -- .5 .5 -- 14 71 17 8.8 3.4 29

05AK35C

C 4.6 31 8.9 26 -- 0.1 .7 -- .2 .1 -- 6.3 74 12 9.4 5.0 26

05AK37A

A 1,050 Dag 72 8.7 .9 4.9 -- -- -- -- .6 -- -- 69 84 5.3 .5 9.9 16

05AK37B

B 16 28 6.2 15 -- -- .2 -- .8 .4 .1 14 65 14 8.4 13 35

05AK37C

C 6.9 27 4.5 18 -- -- 1.2 .1 .3 -- -- 14 65 15 10 10 35

Seward Peninsula (SP)

05AK011A

A 248

O

t 8.8 39 .4 2.3 -- -- -- -- 1.3 .1 .6 9.8 53 1.6 3.7 41 47

05AK011B

B 3.5 36 .8 1.5 -- .1 -- -- 2.3 .6 .5 3.5 45 2.2 5.3 48 55

05AK011C

C 4.2 35 .4 1.3 -- -- -- -- 3.7 -- .7 5.1 47 2.7 2.4 49 54

05AK021A

A 233

O

t 41 19 1.1 1.6 -- .2 -- .1 2.3 .2 .1 39 64 5.5 .5 30 37

05AK021B

B 3.5 44 2.5 2.1 0.2 -- -- -- 3.2 .3 .1 6.2 59 2.4 4.7 34 41

05AK021C

C 3.5 46 1.8 2.1 .2 -- -- -- 3.7 .3 .1 6.5 61 3.0 4.0 32 39

05AK131A

A 128

O

sq 10 45 1.6 2.1 -- -- -- -- 2.4 -- .2 17 68 5.9 9.1 17 32

05AK131B

B 8.8 47 2.0 2.2 -- -- -- .1 2.3 .1 -- 13 66 10 9.4 14 34

05AK131C

C 8.8 48 1.8 2.2 -- -- -- -- 2.5 .2 -- 12 67 6.5 13 15 34
Results and Discussion 

9

Table 3. Ratio of quartz to major soil minerals (calculated on a weight percent basis) in A, B, and C horizon soil samples from three sites in the Yukon-Tanana Upland (YTU) 

and three sites in the Seward Peninsula (SP).

Sample 

identification

Potassium 

feldspar

Plagiocase 

feldspar Goethite Peat

Total 

non-clay minerals

2:1 clay Chlorite Muscovite

Total 

clay 

minerals

Crystalline bedrock (YTU)

05AK33A 4.80 1.30 65.7 0.81 0.31 1.25 2.10 1.82 0.55

05AK33B 4.28 1.46 61.0 1.72 .40 1.61 1.94 2.32 .6405AK33C 5.16 1.75 64.0 3.86 .49 2.00 2.86 4.64 .9405AK35A 7.57 1.36 7.57 .08 .07 .41 1.23 .56 .2005AK35B 3.55 1.29 54.0 1.93 .38 1.57 3.07 7.94 .9205AK35C 3.51 1.20 156 4.95 .42 2.60 3.32 6.24 1.1805AK37A 9.67 1.78 14.5 .13 .10 1.64 17.4 .88 .5505AK37B 4.53 1.87 35.1 1.98 .43 2.01 3.35 2.20 .8005AK37C 5.96 1.49 89.3 1.94 .41 1.76 2.65 2.68 .76

Metasediment bedrock (SP)

05AK011A 97.3 16.9 29.9 3.97 .73 24.3 10.5 .94 .8305AK011B 44.5 23.7 15.5 10.2 .79 16.2 6.72 .75 .65

05AK011C 88.3 27.2 9.54 6.92 .76 13.1 14.7 .73 .66

05AK021A 16.8 11.6 8.04 .47 .29 3.36 37.0 .61 .51

05AK021B 17.8 21.1 13.9 7.16 .75 18.5 9.45 1.32 1.09

05AK021C 25.5 21.9 12.4 7.06 .76 15.3 11.5 1.43 1.17

05AK131A 28.4 21.6 18.9 2.72 .66 7.69 4.99 2.73 1.44

05AK131B 23.6 21.4 20.5 3.77 .71 4.71 5.01 3.27 1.39

05AK131C 26.5 21.7 19.1 3.94 .72 7.34 3.82 3.29 1.42
10 Substrate Geochemistry and Soil Development in Boreal Forest and Tundra Ecosystems in Alaska

Plagioclase feldspar and potassium feldspar show an 

increase with increasing soil depth in the YTU soils but not in 

the SP soils (table 2); however, the ratio of quartz to feldspar 

remains fairly constant with depth for both areas (table 3). 

Because the relative amount of plagioclase remains the same 

with depth, we cannot say that demonstrable feldspar weathering is occurring in these soils. This is in contrast to the findings of Legros (1992), who reports that feldspars in podzolized 

soils of the subalpine region of the Alps dissolved relatively 

quickly (tens of years) with calcic plagioclases less stable than 

sodic, which are less stable than potassic feldspar.

Our soils, however, are greatly influenced by the presence 

of loess (YTU more so than SP), and the ratio of quartz to 

muscovite does not change radically with soil depth (table 3). 

This uniformity means that the ratios are independent of soil 

horizon and therefore of weathering intensity (Evans, 1992). 

The age, source, and weathering of loess versus bedrock, and 

of their relative importance to soil geochemistry, need further 

study.

The clay minerals in these soils are distinctive between 

the two areas (table 2). Soils in the YTU, derived from the 

weathering of metamorphic and intrusive bedrock, possessed 

an abundance of 2:1 clays (smectite and illite) and muscovite 

(together ~20 weight percent). In contrast, the SP soils, developed over schist and quartzite, were dominated by muscovite 

(40 weight percent) with lesser amounts of 2:1 clay and chlorite. The amount of muscovite in these latter soils is indeed 

large and may represent either a source of layered silicates 

or, more probably, a much-reduced rate of soil weathering 

(Nagy, 1995). Little variability with depth is noted for the clay 

minerals for either area (table 2); however, table 3 shows that 

the YTU soils have less muscovite (and total clay) relative 

to quartz with depth. The abundance and distribution of clay 

minerals indicates that some clay formation is occurring in the 

upper horizons of the YTU soils; there is no indication that 

this is occurring in the SP soils.

The simple regression between muscovite, total clay, and 

loss on ignition (peat) (all in weight percent) to the concentration (parts per million, ppm) of Cd and Zn, in the nine soil 

samples (table 2) each from YTU and SP, is shown in figure 4. 

In general, the nine samples from YTU possess lower concentrations of both elements compared to the nine samples from 

the SP, and the values for the two areas comprise two distinct 

populations. Neither Cd nor Zn is significantly correlated with 

loss on ignition in either area (low R2

 values coupled with the 

disproportional influence of a few outlier sample points). Both 

Cd and Zn, however, are strongly and positively correlated 

with muscovite and total clay in the SP samples (fig. 4). These 

differences may be due to fluctuating redox potentials in these 

soils due to differences in seasonal saturation. This major difference in the concentration of Cd and Zn and in the relation 

of Cd and Zn to muscovite and total clay between the two 

regions suggests different sources of the metals. The Zn/Cd 

ratios (around 250) suggest that, for the SP soils, the source of 

Cd and Zn is sphalerite in the loess.

In summary, these data show that although the nine 

samples from the three soil horizons from the YTU and from 

the SP represent similar ecosystems (herbaceous tundra), 

major differences exist between their bulk mineralogy due 

to geology, presence of loess, and the weathering (or lack 

thereof) of primary minerals. Little evidence exists for the 

weathering of feldspar or muscovite. In addition to geology, 

soil formation differences in these two areas are affected by 

differences in climate, elevation, and possibly time (table 2). 

These differences appear to affect the sequestration of Cd and 

Zn, with total clay and muscovite being important to these elements in soils from both areas. In this limited data set, twice as 

much peat was measured in the A and B horizons of the YTU 

samples, as in the SP samples whereas both areas have nearly 

equal amounts of total clay (table 2). SP soils, however, had 

very high values for the clay mineral muscovite. Soil sequential extraction was employed to further elucidate the mode of 

occurrence and potential bioavailability of Cd and Zn.

Chemistry of Soil Sequential Extraction 

Leachates

Figure 5 shows the results for Cd and Zn of the sequential extraction of 20 soil samples from 7 YTU soil profiles. 

Descriptions of the soils used in figure 5 are given in table 4. 

Three of the seven profiles were well-drained silty Inceptisols 

developed over granodiorite bedrock, whereas four of the 

seven were poorly drained silty Gelisols developed over both 

granodiorite and augen gneiss. In addition, five of the sites 

were within the tundra zone and one each in a floodplain and a 

boreal forest zone. The analytical scheme uses extractants that 

increase in the severity with which they attack soil exchange 

sites and mineral structure (table 5). Such schemes provide a 

gradient for the physicochemical association strength between 

elements and solid phases (Chao, 1984). Element solubility in 

such schemes can be related to availability and mobility in the 

environment.

Considerable differences in the proportion of Cd and Zn 

associated with the various extraction leachates is seen in the 

plots (fig. 5). Differences, although not necessarily major, are 

also evident among the three soil horizons. Most of the Cd 

(>50 percent) is easily to conditionally available and is associated with the I, II, and III fractions. Differences among the soil 

horizons are especially evident when comparing the Cd associated with these same fractions in all seven soil profiles shown. 
Results and Discussion 11

Figure 4. Simple regression between muscovite, total clay, and loss on ignition (organic matter) and the concentration (parts per 

million) of cadmium (Cd) and zinc (Zn) in soil samples from the Yukon-Tanana Upland and the Seward Peninsula, Alaska.

Cd, IN PARTS PER MILLION Zn, IN PARTS PER MILLION

Seward Peninsula

Yukon-Tanana Upland

Seward Peninsula

Yukon-Tanana Upland

0 400 800 1200 1600

0

10

20

30

40

50

60

70

80

0 1 2 3 4 5 6 7 8

LOSS ON IGNITION, IN PERCENT

10

20

30

40

50

60

MUSCOVITE, IN PERCENT

0 1 2 3 4 5 6 7 8

0

0 400 800 1200 1600

TOTAL CLAY, IN PERCENT

0 1 2 3 4 5 6 7 8 0 400 800 1200 1600

R2 = 0.96 R2 = 0.94

R2 R2 = 0.62 = 0.90

0

10

20

30

40

50

60

0

10

20

30

40

50

60

70

80

10

20

30

40

50

60

0

10

20

30

40

50

60

0
12 Substrate Geochemistry and Soil Development in Boreal Forest and Tundra Ecosystems in Alaska

Figure 5. Results of the sequential extraction for cadmium and zinc of three soil horizons (A, B, and C) using seven different soil 

profiles and six extractants (see text for explanation and table 4 for soil sample descriptions). All samples are from the Yukon-Tanana 

Upland.

% I % II % III % IV % V % VI

Six sequential soil extractions (top to bottom): 

EXPLANATION

Seven soil profiles: 1, 2, 3, 4, 5, 6, 7. Three soil horizons: A, B, C. 

Zinc

Cadmium

05AK32A

05AK32B

05AK32C

05AK33A

05AK33B

05AK33C

05AK35A

05AK35B

05AK35C

05AK36A

05AK36C

05AK37A

05AK37B

05AK37C

05AK39A

05AK39B

05AK39C

05AK41A

05AK41B

05AK41C

0

20

40

60

80

100

1 2 3 4 5 6 7

05AK41A

05AK41B

05AK41C

05AK37C

05AK39A

05AK39B

05AK39C

05AK32A

05AK32B

05AK32C

05AK33A

05AK33B

05AK33C

05AK35A

05AK35B

05AK35C

05AK36A

05AK36C

05AK37A

05AK37B

0

20

40

60

80

100

PERCENT OF ELEMENT CONCENTRATION EXTRACTED

 TO THE TOTAL OF ALL EXTRACTANTS

PERCENT OF ELEMENT CONCENTRATION EXTRACTED

 TO THE TOTAL OF ALL EXTRACTANTS

1 2 3 4 5 6 7

I

II

III

IV

V

VI
Results and Discussion 13

Total Cd concentrations in the seven soil profiles used 

in the sequential soil extraction analysis had median values 

of 0.12, 0.07, and 0.07 ppm for the A, B, and C horizons, 

respectively, and median Zn values of 56, 71, and 80 ppm. 

None of the bedrock types over which these soils developed 

had measurable Cd (all <1.0 ppm1

); median Zn concentrations1

were as follows: granitoids, 35 ppm; metasediments, 94 ppm; 

diorite-tonalite, 79 ppm; augen gneiss, 52 ppm (Gough and 

others, 2005). 

Cadmium, associated with the I, II, III, and IV soil 

extraction fractions (easily exchangeable, organic, amorphous and crystalline Fe-, Mn-, and Al-oxides/hydroxides) is 

fairly evenly divided among these four fractions and follows 

a general decreasing trend with depth (A-C horizons; fig. 5). 

In addition, a majority of the soil Cd is tied up in these four 

fractions, with commonly <25 percent associated within the 

1

 Estimated crustal abundances of Cd and Zn are 0.11 and 75 ppm, respectively (Emsley, 1991).

IV and V fractions combined. Except for possibly sample 

05AK37 (soils developed over augen gneiss), no meaningful 

differences are observed in figure 5 in the distribution of Cd or 

Zn among the sequential extraction fractions for the two bedrock types examined. Unlike Cd, a majority of the Zn is tied 

up in primary soil minerals (fractions V and VI); in a majority 

of the soil profiles, <20 percent of the Zn appears to be readily 

or conditionally bioavailable.

One additional element of note is calcium (Ca). It is 

highly mobile in northern forests; however, a vast majority of the Ca pool is recycled and reused (Foth, 1990). In 

our sequential extraction study, Ca was found to be mostly 

associated with the I fraction (easily exchangeable as well as 

carbonate) and VI fraction (residual). The Ca in these soils 

that is bioavailable (mobile) generally follows the trend: 

A horizon > B horizon > C horizon. The ratio of CaO/TiO2, 

Table 4. Yukon-Tanana Upland soil samples used in the sequential extraction results shown in figure 5.

Sample 

identification

Soil 

horizons

Soil 

classification

Location Elevation 

(meters)

Ecosystem Geology

Latitude Longitude

05AK32 A, B, C Inceptisol 64.3392 -144.2573 1,050 Tundra Granodiorite

05AK33 A, B, C Inceptisol 64.3394 -144.2506 1,150 Tundra Granodiorite

05AK35 A, B, C Inceptisol 64.3435 -144.2517 1,200 Tundra Granodiorite

05AK36 A, C Gelisol 64.2903 -144.2537 1,030 Floodplain Granodiorite

05AK37 A, B, C Gelisol 64.2913 -144.2603 1,050 Tundra Augen gneiss

05AK39 A, B, C Gelisol 64.3620 -144.2915 1,120 Tundra Augen gneiss

05AK41 A, B, C Gelisol 64.4428 -144.2750 675 Boreal Forest Granodiorite

Table 5. Chemistry and targeted soil fraction of six (I-VI) sequential extractants of soil samples from the Yukon-Tanana Upland, 

Alaska. (Extractions performed using modifications of the method of Hall (1996a; 1996b) and Chao (1984).) 

M, molar; N, normal; g, gram; mL, milliliter]

Extractant Chemistry Targeted soil fraction

I 1 M sodium acetate (pH 5) Easily exchangeable component (adsorbed as well as 

carbonate)

II 0.1 M sodium phosphate (pH 10) Labile organic component

III 0.25 M hydroxylamine hydrochloride and 0.25 N

hydrochloric acid

Amorphous Fe- and Mn-oxide and some amorphous 

Al-oxide component

IV 1 M hydroxylamine hydrochloride and 25 percent 

acetic acid

Crystalline Fe-oxide; monosulfide and secondary 

sulfide component

V 1 g potassium chlorate and 10 mL hydrochloric acid Sulfur-bound component 

VI Four-acid digestion (hydrofluoric, hydrochloric, 

perchloric, and nitric)

Total residual component
14 Substrate Geochemistry and Soil Development in Boreal Forest and Tundra Ecosystems in Alaska

discussed above for figure 3A, was also higher in the A horizon than deeper in the soil profile. Although the I fraction 

would release Ca from soil carbonates, these low pH soils 

(pH 3.8 – 6.3) have an abundance of both organic acids and 

carbonic acid in the A and B horizons that would affect carbonate dissolution. In addition, the bulk mineralogy for these 

soils (table 2) showed only fractions of a weight percent of 

calcite and dolomite. Further, we did not observe caliche in 

these soils. Van Cleve and others (1991) report that caliche can 

form (especially in interior Alaska floodplain soils) because of 

high summer temperatures that accompany low precipitation 

(300–400 millimeters per year, mm y-1) and relatively high 

evapotranspiration (>450 mm y-1).

Soil Loess and Geochemical Signatures

Soils of both the Yukon-Tanana Upland (YTU) and 

Seward Peninsula (SP) have a silty to silty-loam texture, 

especially in the A and B horizons. An important question is 

whether the silt fraction is predominantly eolian dust (Quaternary to Holocene, modern, or a mixture) or the result of in situ 

physical processes of rock shattering and cryoturbation. This 

distinction is important in the interpretation of soil geochemistry because loess deposition and soil weathering can be interpreted as competing processes (Muhs and others, 2004), and 

geochemical signatures related to bedrock thus are potentially 

confounded. These authors state that major loess deposition in 

central Alaska took place in the late Quaternary to Holocene 

(<50 – 30 thousand years ago, Ka) and that modern deposition 

in the inland area of the YTU and SP, sampled in this study, is 

now occurring at very low rates. 

The samples in this study were not geochemically 

analyzed on the basis of particle size fractionation, so geochemical data on just the silt-sized portion are not available. 

Instead, the soils were sieved to <10 mesh and then ground to 

<100 mesh prior to analysis.

Figure 6 presents plots of CaO versus MgO and Al2O3

versus Fe2O3 in soils developed over both the YTU and 

SP bedrock types. The correlation between CaO and MgO is 

poor, which is expected in soils low in carbonate and developed from metamorphic and intrusive rocks (YTU) and from 

metasedimentary rocks (SP). In addition, the two bedrock 

types (metamorphic and intrusive and metasediments) are 

moderately well segregated in plots based on CaO and MgO 

(fig. 6). 

A linear correlation exists between Al2O3 and Fe2O3 in the 

A horizon for both bedrock types; this relation is not present in 

the B and C horizon soils. This correlation implies that Fe and 

Al are coupled in the upper soil horizon and is reflective of the 

presence of oxides and (or) hydroxides. As discussed above, 

Cd is one element closely associated with soil oxides and (or) 

hydroxides. The absence of any correlation between our plots 

of CaO and MgO and of Al2

O3 and Fe2O3 with the geochemical signatures reported by Muhs and others (2003b) for central 

Alaskan late Quaternary loess (shown by the shaded ovals in 

fig. 6) suggests that the silty material in our soils is probably 

more locally derived dust as well as the product of in-place 

bedrock shattering. 
Results and Discussion 15

Figure 6. Plots of CaO versus MgO and Al2O3 versus Fe2O3 in three soil horizons segregated by bedrock type. Also plotted are the 

values for central Alaska loess of late Quaternary age (estimated from Muhs and others, 2003b). n, number of samples. 

EXPLANATION

Central Alaskan 

Loess Signature

(estimated from Muhs and others, 2003b)

Generalized rock type

Crystalline (n=45)

Metasediment (n=7)

CaO, IN PERCENT

MgO, IN PERCENT MgO, IN PERCENT MgO, IN PERCENT

Al2O3, IN PERCENT

Fe2O3, IN PERCENT Fe2O3, IN PERCENT Fe2O3, IN PERCENT

0

4

5

5

0 0

1

2

3

0

1

2

3

4

0 1 2 3 4

1

2

3

4

5

1

3

5

7

9

11

1

3

5

7

9

11

1

3

5

7

9

11

0 5 10 15 20

A horizon A horizon

B horizon B horizon

C horizon

1 2 3 4

0 1 2 3 4

0 5 10 15 20

0 5 10 15 20

C horizon
16 Substrate Geochemistry and Soil Development in Boreal Forest and Tundra Ecosystems in Alaska

Summary

Studies of silty textured soils developed over crystalline 

bedrock terrane (metamorphic and intrusive from the YukonTanana Upland and schist and quartzite from the Seward 

Peninsula) were examined for their differences in chemical 

weathering and for possible landscape geochemical patterns. 

Chemical weathering signature differences were also examined on the basis of the ecosystem within which the soils 

developed (boreal forest and tundra). 

There are major differences in the nonclay and clay mineralogy of the soils from the two study areas. Of the nonclay 

minerals, quartz was the most abundant followed by peat 

(“mineral”) > plagioclase feldspar > goethite. The absolute 

amount of plagioclase and potassium feldspar increases with 

increasing depth in the YTU soils, but the relative amount 

of feldspar to quartz does not. This trend would suggest, 

therefore, that very little weathering of feldspar is occurring 

in these soils. Of the clay minerals, soils in the YTU, developed over metamorphic and intrusive bedrock, possessed an 

abundance of 2:1 clays and muscovite, whereas the SP soils, 

developed over metasediments, were dominated by muscovite 

with lesser amounts of 2:1 clay and chlorite. In the YTU soils, 

the relative amount of total clay to quartz did decrease with 

soil depth (more clays in the upper soil horizons), which also 

suggests little weathering in these soils.

Examination of the ratio of mobile (K2

O, CaO, and 

Fe2O3) to immobile (TiO2) major oxides showed that very little 

difference exists in the chemical weathering of soils developed 

among the ecosystems tested (hypothesis 2). This means that 

in the short-term, changes in weathering signatures due to 

climate change may be too subtle to be easily detected using 

these methods. Differences were observed among the bedrock 

types, especially when comparing soils developed over schist 

and quartzite with soils developed over metamorphic and 

intrusive bedrock. We assume that the age of these soils is late 

Quaternary to Holocene; however, it is impossible to say for 

certain that geochemical differences are due exclusively to differences in bedrock geochemistry or to differences in weathering history. 

A loss of Cd with soil depth is seen for soils developed 

over metamorphic and intrusive bedrock in the boreal forest. 

This trend is related to the mobility of Cd in these soils as 

well as to its biogenic cycling. Zinc does not display similar 

biogenically mediated trends and is less bioavailable than Cd. 

Sequential partial extraction results on these soils support this 

distinction between the relative bioavailability of Cd versus 

Zn. 

Comparison of the relation between CaO and MgO and 

Al2

O3 and Fe2O3 for A, B, and C horizon soils with values 

for late Quaternary loess from central Alaska (Muhs and 

others, 2003b) shows that the silty material in our soils does 

not match the loess signature and is most likely younger 

and more locally derived. Finally, major differences were 

observed in the proportion of most elements among the A, B, 

and C horizon material sequestered in various soil fractions as 

measured by sequential soil extractions. These trends followed 

such variables as the decrease in organic matter, the change in 

clay minerals, and the change in the proportion of oxides and 

hydroxides with depth.

In this study we controlled the major factors that influence soil development except time. We assume that these soils 

are all approximately the same age, and their general uniformity in physical appearance, mineralogy, and chemistry lends 

support to this assumption. This uniformity underscores the 

slow nature of soil development in cold regions and the long 

periods of time that are required to affect observable changes. 

Should changes in the climate of the subarctic accelerate 

(specifically, permafrost melting and the attendant oxidation of 

trapped organic matter), changes in the mineralogical and geochemical soil development processes could also be expected to 

accelerate (Keller and others, 2007). 

Acknowledgments

We thank Sumatomo Metal Mining Co., Limited, and 

Teck Cominco Limited for their logistical support at the 

Pogo Mine camp, Jim Vohden and the Alaska Department of 

Natural Resources Division of Mining, Land and Water for 

contributing helicopter and logistical support, and the Alaska 

Department of Natural Resources Division of Forestry for use 

of their helipad at Delta Junction. Chemical analyses were performed in the USGS Denver Laboratories by Monique Adams, 

Alan Meier, Zoe Ann Brown, and Cathy Ager. Extremely 

helpful critical reviews were contributed by Daniel Muhs, 

Ruth Wolf, and Gilpin Robinson, USGS, and Mark Clark, 

Natural Resources Conservation Service, Alaska.

References Cited

Bundtzen, T.K., Reger, R.D., Laird, G.M., Pinney, D.S., 

Clautice, K.H., Liss, S.A., and Cruse, G.R., 1994, Progress 

report on the geology and mineral resources of the Nome 

Mining District: State of Alaska Department of Natural 

Resources, DGGS Public-Data File 94–39, 19 p. plus map.

Campbell, I.B., and Claridge, G.G.C., 1992, Soils of cold 

climate regions, in Martini, I.P., and Chesworth, W., 

eds., Weathering, soils and paleosols: London, Elsevier, 

p. 183–224.

Chao, T.T., 1984, Use of partial dissolution techniques in geochemical exploration: Journal of Geochemical Exploration, 

v. 20, p. 101–135.
References Cited 17

Crock, J.G., Arbogast, B.F., and Lamothe, P.J., 1999, Laboratory methods for the analysis of environmental samples, 

in Plumlee, G.S., and Logsdon, M.J., eds., Reviews in 

Economic Geology Volume 6A, The Environmental Geochemistry of Mineral Deposits, Part A—Processes, Techniques, and Health Issues: Society of Economic Geologists, 

p. 265–287.

Day, W.C., Aleinikoff, J.N., Roberts, Paul, Smith, Moria, 

Gamble, B.M., Henning, M.W., Gough, L.P., and Morath, 

L.C., 2003, Geologic map of the Big Delta B-2 quadrangle, 

east-central Alaska: U.S. Geological Survey Geologic 

Investigations Series I-2788, 1:63,360 scale, map with interpretations (http://pubs.usgs.gov/imap/i-2788/i-2788.pdf).

Day, W.C., and O’Neill, J.M., in press, Geochemical analyses 

for bedrock and mineralized rocks, geologic field notes, and 

field photographs from the Big Delta B-1 quadrangle, eastcentral Alaska: U.S. Geological Survey Open-File Report 

2008–1115.

Day, W.C., O’Neill, J.M., Aleinikoff, J.N., Green, G.N., Saltus, R.W., and Gough, L.P., 2007, Geologic map of the Big 

Delta B-1 quadrangle, east-central Alaska: U.S. Geological 

Survey Scientific Investigations Map 2975 (http://pubs.usgs.

gov/sim/2007/2975/).

Dilworth, Katherine, Ebert, Shane, Mortensen, J.K., Rombach, C.S., and Tosdal, R.M., 2002, Reduced granites and 

gold veins in the Pogo area, east-central Alaska: Geological 

Society of America, Abstracts with Programs, v. 34, no. 6, 

p. 114.

Dusel-Bacon, Cynthia, and Hansen, V.L., 1992, High-pressure 

amphibolite-facies metamorphism and deformation within 

the Yukon-Tanana and Taylor Mountain terranes, eastern 

Alaska, in Bradley, D.C., and Dusel-Bacon, Cynthia, eds., 

Geological studies in Alaska by the U.S. Geological Survey, 

1991: U.S. Geological Survey Bulletin 2041, p. 140–159.

Dusel-Bacon, Cynthia, Lanphere, M.A., Sharp, W.D., Layer, 

P.W., and Hansen, V.L., 2002, Mesozoic thermal history and 

timing of structural events for the Yukon-Tanana Upland, 

east-central Alaska—40Ar/39Ar data from metamorphic and 

plutonic rocks: Canadian Journal of Earth Sciences, v. 39, 

no. 6, p. 1013–1051.

Eberl, D.D., 2003, User guide to RockJock—A program for 

determining quantitative mineralogy from X-ray diffraction 

data: U.S. Geological Survey Open-File Report 2003–078, 

36 p. (ftp://brrcrftp.cr.usgs.gov/pub/ddeberl/RockJock).

Eberl, D.D., 2004, Quantitative mineralogy of the Yukon River 

system—changes with reach and season, and determining sediment provenance: American Mineralogist, v. 89, 

no. 11–12, p. 1784–1794.

Emsley, John, 1991, The elements: Oxford, UK, Clarendon 

Press, 251 p.

Evans, L.J., 1992, Alteration products at the earth’s surface—

the clay minerals, in Martini, I.P., and Chesworth, W., eds., 

Weathering, soils and paleosols: London, UK, Elsevier, 

p. 107–125.

Ferrians, O.J., Jr., 1965, Permafrost map of Alaska: 

U.S. Geological Survey Miscellaneous Investigations 

Series Map I–445.

Foth, H.D., 1990, Fundamentals of soil science: New York, 

John Wiley and Sons, 360 p.

Gough, L.P., Crock, J.G., and Day, W.C., 2002, Cadmium 

accumulation in browse vegetation, Alaska—implication for 

animal health, in Skinner, H.C.W., and Berger, A.R., eds., 

Geology and health—Closing the gap: Oxford University 

Press, p. 77–78.

Gough, L.P., Crock, J.G., Day, W.C., and Vohden, Jim, 2001, 

Biogeochemistry of arsenic and cadmium, Fortymile River 

watershed, east-central Alaska, in Gough, L.P., and Wilson, 

F.H., eds., Geologic studies in Alaska by the U.S. Geological Survey: U.S. Geological Survey Professional 

Paper 1633, p. 109–126 (http://pubs.er.usgs.gov/usgspubs/

pp/pp1633).

Gough, L.P., Day, W.C., Crock, J.G., Gamble, B.M., Henning, M.W., Ager, C.M., Meier, A.L., Briggs, P.H., Brown, 

Z.A., and Adams, M., 2005, Regional geochemical results 

from the analyses of rock, soil, and vegetation samples—

Big Delta B-2 quadrangle, Alaska: U.S. Geological Survey 

Open-File Report 2005–1431, 12 p. plus 12 tables 

(http://pubs.usgs.gov/of/2005/1431/).

Hall, G.E.M., Vaive, J.E., MacLaurin, A.I., 1996a, Analytical 

aspects of the application of sodium pyrophosphate reagent 

in the specific extraction of the labile organic component of 

humus and soils: Journal of Geochemical Exploration, v. 56, 

p. 23–36.

Hall, G.E.M., Vaive, J.E., Beer, R., Hoashi, M., 1996b, Selective leaches revisited with emphasis on the amorphous Fe 

oxyhydroxide phase extraction: Journal of Geochemical 

Exploration, v. 56, no. 1, p. 59–78.

Jenny, Hans, 1980, The soil resource: Origin and behavior: 

New York, Springer-Verlag, 377 p.

Keller, K., Blum, J.D., and Kling, G.W., 2007, Geochemistry 

of soils and streams on surfaces of varying ages in arctic 

Alaska: Arctic, Antarctic, and Alpine Research, v. 39, no. 1, 

p. 84–98.

Legros, J.P., 1992, Soils of alpine mountains, in Martini, I.P., 

and Chesworth, W., eds., Weathering, soils and paleosols: 

New York, Elsevier, p. 155–181.
18 Substrate Geochemistry and Soil Development in Boreal Forest and Tundra Ecosystems in Alaska

McArthur, D.F.E., Huang, P.M., and Kozak, L.M., 2001, 

Impact of long-term cultivation on the status of organic matter and cadmium in soil: Canadian Journal of Soil Science, 

v. 81, no. 3, p. 349–355.

Muhs, D.R., Ager, T.A., Been, Josh, Bradbury, J.P., and Dean, 

W.E., 2003a, A late Quaternary record of eolian silt deposition in a maar lake, St. Michael Island, western Alaska: 

Quaternary Research, v. 60, no. 1, p. 110–122.

Muhs, D.R., Ager, T.A., Bettis, A.E. III, McGeehin, J.P., Been, 

J.M., Begét, J.E., Pavich, M.J., Stafford, T.W., Jr., and Stevens, DeAnne S.P., 2003b, Stratigraphy and palaeoclimatic 

significance of late Quaternary loess—palaeosol sequences 

of the Last Interglacial-Glacial cycle in central Alaska: Quaternary Science Reviews, v. 22, no. 18–19, p. 1947–1986.

Muhs, D.R., McGeehin, J.P., Beann, Jossh, Fisher, Eric, 2004, 

Holocene loess deposition and soil formation as competing 

processes, Matanuska Valley, southern Alaska: Quaternary 

Research, v. 61, no. 3, p. 265–276.

Nagy, K.L., 1995, Dissolution and precipitation kinetics of 

sheet silicates, in White, A.F., and Brantley, S.L., eds., 

Chemical weathering rates of silicate minerals: Mineralogical Society of America, Reviews in Mineralogy, v. 31, 

p. 173–233.

Nowacki, G.J., Spencer, Page, Fleming, Michael, Brock, Terry, 

and Jorgenson, Torre, 2002, Unified ecoregions of Alaska, 

2001: U.S. Geological Survey Open-File Report 2002–297, 

1:4,000,000-scale map.

Selby, David, Creaser, R.A., Hart, C.J.R., Rombach, C.S., 

Thompson, J.F.H., Smith, M.T., Bakke, A.A., and Goldfarb, 

R.J., 2002, Absolute timing of sulfide and gold mineralization—A comparison of Re-Os molybdenite and Ar-Ar mica 

methods from the Tintina gold belt, Alaska: Geology, v. 30, 

no. 9, p. 791–794.

Taggart, J.E., ed., 2002: Analytical methods for chemical analysis of geologic and other materials, U.S. Geological Survey: U.S. Geological Survey Open-File Report 

2002-223 (available online at http://pubs.usgs.gov/of/2002/

ofr-02–0223/).

Till, A.B., and Dumoulin, J.A., 1994, Geology of Seward Peninsula and Saint Lawrence Island, in Plafker, George, and 

Berg, H.C., eds., Geology of Alaska: Boulder, Colo., Geological Society of America, The Geology of North America, 

v. G–1, p. 141–152.

Till, A.B., Dumoulin, J.A., Gamble, B.M., Kaufman, D.S., 

and Carroll, P.I., 1986, Preliminary geologic map and fossil 

data, Solomon, Bendeleben, and southern Kotzebue quadrangles, Seward Peninsula, Alaska: U.S. Geological Survey 

Open-File Report 86–276, 71 p. plus 3 plates.

Van Cleve, K., Chapin, F.S. III, Dryness, C.T., and Viereck, 

L.A., 1991, Element cycling in Taiga forests—State-factor 

control: BioScience, v. 41, no. 2, p. 78–88.

Van Cleve, Keith, and Yarie, J., 1986, Interaction of temperature, moisture, and soil chemistry in controlling nutrient 

cycling and ecosystem development in the Taiga of Alaska, 

in Van Cleve, K., Chapin, F.S. III, Viereck, L.A., Dyrness, C.T., and Flanagan, P.W., eds., Forest ecosystems in 

the Alaskan taiga—A synthesis of structure and function: 

Springer-Verlag, New York, p. 160–189.

Werdon, M.B., Stevens, D.S.P., Newberry, R.J., Szumigala, 

D.J., Athey, J.E., and Hicks, S.A., 2005, Explanatory 

booklet to accompany geologic, bedrock, and surficial maps 

of the Big Hurrah and Council areas, Seward Peninsula, 

Alaska: State of Alaska Department of Natural Resources, 

DGGS Report of Investigations 2005–1, 24 p.

Wilson, F.H., Smith, J.G., and Shew, Nora, 1985, Review 

of radiometric data from the Yukon Crystalline Terrane, 

Alaska and Yukon Territory: Canadian Journal of Earth Sciences, v. 22, no. 4, p. 525–537. 

Gough and others—Substrate Geochemistry and Soil Development in Boreal Forest and Tundra Ecosystems in Alaska —Scientific Investigations Report 2008–5010

Printed on recycled paper

ISBN