Holocene palaeoenvironmental record preserved in a paraglacial alluvial fan, Sunwapta Pass, Jasper National Park, Alberta, Canada

CATENA ELSEVIER

Catena 22 (1994) 227-248

Holocene palaeoenvironmental record preserved in a paraglacial alluvial fan, Sunwapta Pass, Jasper National Park, Alberta, Canada A l w y n n e B. B e a u d o i n a, R o g e r H. K i n g b aArchaeological Survey, Provincial Museum of Alberta, 12845 - 102nd Avenue, Edmonton, Alta., T5N OM6, Canada bDepartment of Geography, University of Western Ontario, London, Ont., N6A 5C2, Canada

Abstract The soil stratigraphy of a 1.5 m section in the distal portion of a paraglacial alluvial fan in Sunwapta Pass, Jasper National Park, has been examined as part of a long-term investigation into Holocene palaeoenvironments of the area. The section is complex and its characteristics are a result of both episodic sediment inputs and pedogenesis. A series of sediments comprising debris-flows and aeolian material including three discrete tephra layers (Mazama, St. Helens Yn, Bridge River) underlie the present day soil. Multiple criteria, including stratigraphy, radiocarbon dates, glass shard morphology, and electron microprobe analysis of glass and titanomagnetite composition, confirmed the identity of the tephras. Most fan development occurred before deposition of Mazama tephra. Pedogenesis has been active on the fan throughout the Holocene. Soils have formed between phases of sediment deposition during periods of greater relative site stability. Soil horizonation is best developed where tephric material has influenced soil chemistry and clay mineralogy leading to the formation of Brunisols. The sequence of events inferred from the Icefield Fan's stratigraphy accord well with the Holocene palaeoenvironmental history inferred from other sites in the Canadian Rockies.

I. Introduction Numerous well developed alluvial fans in the Canadian Rockies represent important storage areas for geomorphic material and attest to a previous phase of landscape development in which high sediment aggradation rates were associated with an abundant debris supply. In contrast, present rates of aggradation on these hillslopes are relatively low and many of the fans show features of incision and degradation. The term "paraglacial" has previously been used to describe nonglacial processes and a time when the landscape, having been conditioned by glaciation, contained detrital 0341-8162/94/$07.00 © 1994 Elsevier Science B.V. All rights reserved S S D I 0 3 4 1-8 16 2 ( 9 4 ) E 0 0 2 4 - T

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material in amounts far in excess of more normal material supply by subaerial weathering processes (Church and Ryder, 1972). The poorly-sorted bouldery nature of many of the deposits found in the alluvial fans suggest that debris-flows have played a signifcant role in their formation. However, the low frequency of such flows under present conditions suggests that the fans are largely relict features in the present-day landscape, In the south central Canadian Rockies the presence of Mazama ash dated at 6800 yr BP (Bacon, 1983) at depths of not more than 2 m in the fans indicates that most fan deposition occurred earlier and that the fans have been relatively stable since that time. In instances where streams have incised the fans or where highway construction has exposed sections, the sequence of deposits revealed is invariably complex. In addition to debris-flow deposits, fluvial, and aeolian deposits also occur. Volcanic ashes, when present, provide invaluable marker beds and the presence of buried soils bear witness to the episodic nature of past sediment accumulation. These fans are believed to contain some of the most complete stratigraphic records of Holocene environmental change in the Canadian Rockies. Although the palaeoenvironmental records preserved in lake sediments and peat bogs are probably more continuous, the alluvial fans give a different perspective in that they include a palaeosol record and provide evidence of the pedogenic response to environmental change. This paper examines the stratigraphic record preserved in the Icefield Fan in Sunwapta Pass, Jasper National Park (Fig. 1). The paper focuses on the sequence of deposits present at this location and the pedogenic response to the radical changes in parent materials that have occurred during the lifetime of the fan.

2. Study area and site The Icefield Section (informal name) (latitude 52°13~9" N, longitude 117°12t23" W, elevation ca. 2010 masl) is in a road-cut through the toe of a large alluvial fan in Sunwapta Pass, upvalley from the Athabasca Glacier (Bowyer, 1978) (Fig. 1). Sunwapta Pass is in the upper subalpine ecozone (Holland and Coen, 1982) characterized by forest, predominantly of Engelmann spruce and subalpine fir (Picea engelmannii and Abies lasiocarpa). Open vegetation on the lower slopes of alluvial fans, including the Icefield Fan (Fig. 2), is dominated by shrub willows (Salix spp.), with other shrubs including dwarf birch (Betula glandulosa) and cinquefoil (Potentilla spp.). The almost treeless Sunwapta Pass valley floor contains a series of wetlands, vegetated mainly by sedges ( Cyperaceae). Only discontinuous and limited climate data (5-13 years' record for different parameters) are available from the Columbia Icefield area. These data show short summers with mean July temperatures of 9.1 °C. Winters are long, cold (mean January temperatures o f - 14.2°C) and snowy. Total annual precipitation is 930 mm, of which 70% falls as snow (Atmospheric Environment Service, 1982). At this elevation (about 2035 m at the Park Boundary), the growing season is short (Janz and Storr, 1977).

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229

Fig. 1. Location of the Sunwapta Pass area (ll), Jasper National Park, Alberta, and other localities mentioned in the text. 3. Materials and methods

A total of 19 separate layers were identified in the Icefield Section and described according to established procedures (Dumanski, 1978). Two of the layers were too thin and discontinuous to be sampled. Volumetric samples were taken from the other 17 layers and stored in labelled polyethylene bags. All samples were initially air dried and fractionated using a 2 mm sieve. Particle size analysis was performed using the pipette method (Day, 1965). Chemical pretreatments were employed for the removal of organic matter, secondary carbonates and amorphous iron oxyhydroxide coatings (Jackson, 1956; Kittrick and Hope, 1963; Mehra and Jackson, 1960). Sand sizes were fractionated by dry-sieving and the fine clay fraction ( < 0.2 #m) determined by centrifugation (Jackson, 1956). Total carbonates were determined gasometrically using the modified Chittick apparatus (Dreimanis, 1962). pH was determined on a 1 : 2 soil to 0.01 M CaC12 suspension using a combination electrode system (Sheldrick, 1984). Organic carbon was determined using a modified Walkley-Black technique (Hesse, 1971). Organic

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230

',X_,,(fz Ah

S

St HelensY

~/)

M

Mazama

~.. ~

Charcoal/Ah

L-... :~] Mainly silt

B

Tephra BridgeRiver

~

C~

Stones Debrisflow/colluviurn

Fig. 2. Photograph and profile sketch of the Icefield Section. Photographed by R.H.K. in 1977.

matter content was estimated by multiplying the organic carbon values by the conventional Van Bemmelen constant (1.724). Organic carbon was also determined using a modified Walkley-Black procedure on sodium pyrophosphate extracts (Bascomb, 1968) and humic and fulvic acids fractionated using Kononova's method (Kononova, 1966). Clay minerals were identified using X-ray diffraction analysis performed on clay fractions following centrifugation using a General Electric XRD-5 X-ray diffractometer with a nickel-filtered Cu Kc~ radiation source and a scanning speed of 2 ° 20/ rain. Oriented clay mounts were prepared on porous ceramic plates using filtration. Five pretreatments were employed, including Mg-saturated clay (air-dried at 0% relative humidity; ethylene glycol solvated) and K-saturated clay (air-dried at 0% relative humidity; heated for 1 h at 300°C; heated for l h at 550°C). An X-ray diffraction analysis was also performed on samples from the silt (63-2 #m) and

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231

fine sand (106-63 #m) fractions that had been attached to petrologic glass slides using clear nail polish. The diffractograms were interpreted by standard methods (Brindley and Brown, 1980) and the clay minerals expressed as relative amounts as a function of diffraction peak intensity. With each X-ray scan a quartz standard was run to ensure accurate diffraction peaks. Amorphous clay was investigated by selective dissolution using NaOH (Hashimoto and Jackson, 1960). Selective dissolution of various forms of Fe and A1 known to be pedogenically active were performed using solutions of sodium citrate-bicarbonate-dithionite, following the procedure of Mehra and Jackson (1960), acid (pH 3.0) ammonium oxalate, following a 4 hour extraction in the dark using a soil : solution ratio of 1 : 40 and sodium pyrophosphate (Sheldrick, 1984), on oven-dried soil ground to pass a 100-mesh sieve (150 #m). Cation exchange capacity (C.E.C.) was determined using Na + as the index ion (Hesse, 1971). Exchangeable Ca 2+ and Mg 2+ were determined on a 2 N sodium chloride extract (Sheldrick, 1984). Fe, A1, Ca, Mg and Na concentrations in the extracts were determined by atomic absorption spectrophotometry using appropriate lamps, flame conditions and calibration standards. Optical microscopy was used to examine volcanic glass shards within the fine sand fraction of selected samples. At least 200 shards were identified per sample, classified by morphology and subsamples mounted, polished and carbon coated prior to electron microprobe analysis. Glass-encased titanomagnetites were also removed from the fine sand fractions of selected samples and prepared for electron microprobe analysis. Compositional analyses were performed using a Materials Analysis Corporation Model 400 electron microprobe equipped with three wavelength dispersive spectrometers. The operating conditions and calibration standards used were identical to those used by King et al. (1982). In addition, charcoal samples from the Icefield Section and from another nearby section (IF-80) were dated by conventional radiocarbon dating. The ages are quoted in uncalibrated radiocarbon years and the errors represent 68.3% confidence limits.

4. Results

4.1. Stratigraphy Roadwork over a number of years has exposed a number of sections through the distal portion of the fan which permit a reconstruction of the sequence of sedimentation. The most complete record is provided by the Icefield Section (Table 1; Fig. 2) which exposes the top 1.5 m of the fan's stratigraphy. It shows a sequence of silty textured deposits interdigitated with gravelly deposits, the latter probably representing episodic debris-flows. A number of thin discrete organic layers, often containing charcoal fragments, are also distributed throughout the section. A series of radiocarbon dates (Fig. 3) based on charcoal from layers in the Icefield Section and an adjacent section, IF-80, previously described by King (1984), provide chronologic control for the stratigraphy. Essentially, the Icefield Section comprises nine deposits. Two deposits, identified as

232

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Table 1 Profile description of the Icefield Section Horizon

Depth (cm)

Description

Ahk

0-16

Dark greyish brown (2.5Y4/2); silt loam; structureless; abundant roots; few stones; clear smooth boundary; moderately alkaline; Sample 1.

Bhk

16- 32

Very dark greyish brown (10YR3/2); silt loam; structureless; abundant roots; few stones; clear smooth boundary; moderately alkaline; Sample 2.

IIAh

32-34

Black (10YR2.5/1); silty clay; structureless; plentiful fine roots; few stones; abrupt, smooth boundary; moderately alkaline; Sample 3.

IIBm

34-40

Very dark greyish brown (10YR3/2); clay loam; structureless; abundant roots; few stones; abrupt irregular boundary; moderately alkaline; Sample 4.

IIIAh

40-42

Very dark grey (10YR3/1); silty clay loam; structureless; few roots; few stones; abrupt irregular boundary; moderately alkaline; Sample 5.

IIIBml

42-45

Bridge River tephra. Olive brown (2.5Y4/4); silt loam; structureless; few roots; stoneless; abrupt, smooth boundary; moderately alkaline; Sample 6.

IVBm2

45-56

Dark greyish brown (2.5Y4/2); silt loam; medium blocky; few roots; few stones; clear, smooth boundary; moderately alkaline; Sample 7.

VAh

56

Some areas contain a thin dark coloured layer, probably a buried Ah. Not sampled.

VBh

56-64

Olive brown (2.5Y4/4); silt loam; medium blocky; few roots; few stones; clear smooth boundary; moderately alkaline; Sample 8.

VIBm

64-66

St. Helens Yn tephra. Dark yellowish brown (10YR4/4); silt loam; structureless; few roots; few stones; abrupt smooth boundary; moderately alkaline; Sample 9.

VIIAh

66-68

Dark brown (10YR3/3); silty clay loam; structureless; few roots; few stones; abrupt smooth boundary; moderately alkaline; Sample 10.

VIIBm

68-72

Dark yellowish brown (10YR4/4); silty clay loam; structureless; few roots; few stones; gradual smooth boundary; moderately alkaline; Sample 11.

VIICk

72-104

Olive brown (2.5Y4/4); loam; structureless, few roots; stones common, gravelly; abrupt irregular boundary; moderately alkaline; Sample 12.

VIIIAh

104-106

Very dark greyish brown (2.5Y5/2); loam; structureless; few roots; stoneless; abrupt irregular boundary; moderately alkaline; Sample 13.

VIIIBm

106-110

Mazama tephra. Yellowish brown (10YR5/8); silt loam; structureless; very few roots; stoneless; abrupt wavy boundary; moderately alkaline; Sample 14.

IXAh

110-111

Thin charcoal layer (not sampled).

IXBm

111 - 113

Light olive brown (2.5Y5/6); silt loam; medium blocky; very few roots; few stones; clear smooth boundary; moderately alkaline; Sample 15.

IXCk I

113-116

Olive brown (2.5Y4/4); loam; structureless; very few roots; stones common, gravelly; clear smooth boundary; moderately alkaline; Sample 16.

IXCk 2

116-150+

Olive (5Y4/4); silt loam; structureless; very few roots; stones common, gravelly; moderately alkaline; Sample 17.

Terminology follows Dumanski (1978).

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233

separate debris-flows, comprise numerous poorly sorted angular clasts of the local Lower Paleozoic bedrock in a calcareous silt/silt loam matrix. The remaining deposits in the section are silty loam to silty clay in texture, generally structureless, moderately alkaline with pH values ranging from 7.4 to 7.7, and with variable carbonate contents, ranging from 1.0 to 38.6%. Their silty nature suggests that they may be aeolian in origin. However, the presence of stones in these deposits indicates either a more complex origin or post-depositional modification. Deposits beneath the Icefield Section appear to comprise a continuous sequence of poorly differentiated debris-flows. Boundaries between the various deposits in the Icefield Section are generally clear and smooth, occasionally abrupt and wavy, and frequently associated with dark coloured layers containing charcoal fragments. Layering within individual deposits is common, with colour, texture and structure changes apparently reflecting soil development.

4.2. Tephra identification Identification of the tephras in the section is important because of their utility as stratigraphic markers of local and regional significance and because of their role in soil development. Although the radiocarbon dates (Fig. 3) from the Icefield Fan support the identification of the three tephra layers as Mazama, St. Helens Yn and Bridge River tephra, tephric material is clearly distributed through a number of the deposits in the Icefield Section. In the field, the tephras range in colour from olive brown to dark yellowish brown (Table 1). Field criteria for tephra identification tend to be insufficient because carbonate-rich bedrock in the area may weather to produce light-coloured horizons and podzolization may lead to bleached horizons. King (1984) observed that light-coloured Bridge River tephra in near-surface situations may be confused with Ae horizons (Valentine et al., 1987). The tephra layers in the Icefield Section are characterized (Tables 2 and 3) by their high silt content and their relatively low carbonate and organic matter contents. The Bridge River tephra has a higher sand content than either of the others, probably because this site is closer to its source. Petrographic examination allowed the distinction of tephras by their high proportion of glass shards (Table 2). The non-glass component of these samples consist mainly of calcite, quartz and opaque fragments, possibly derived from the local sediments and thus a contaminant to the tephra. The thinnest tephra layer (Sample 9) contained the greatest proportion of such material (Table 4). Other samples in the section also showed considerable quantities of volcanic glass, up to 51.5% in Sample 13 (Table 2). This suggests that, although the tephras may have been deposited rapidly in discrete layers, they were redistributed by geomorphic processes. Because the tephras are in the distal areas of their plumes and therefore are predominantly silt-sized, they are particularly susceptible to reworking by aeolian activity and cryoturbation. Some near-surface soil horizons contain considerable quantities of glass shards suggesting that some tephra is continuing to be redistributed in the landscape.

234

A.B. Beaudoin, R.H. King / Catena 22 (1994) 227 248 Sample number

Depth (cm) --0

Ahk

",.e ( ;r,:d*'. ;.e ~.,\- Jt

Odhic Melanic Brunisol

-20

Bhk IIAh dBm IIIAh IlIBm~

40 : • ...

60

8 9 10

~.:. : • ". . . .

~" ~ ~ ' ~

11

~

12

f'i

- 80

Palaeosol B Orlhic Eutric Brunisol

VAh

(~

~ ~ / - - " ,

Palaeosol A Orthic Eulric Brunisol

~.ij

VBh

Palaeosol C Orthic Eutric Brunisol

VIIBm D~ c~

Palaeosol

c;,l VllCk OrPhiReg°sol c

100 VIIIAh VIIIBm IXAh IXBm

13 14 15 16

IXCkl

- 120

IXCk2

17

Ah

~

Charcoal/Ah

Mainlysilt

[~

Debrisflow

Tephras

B BridgeRiver 8 St HelensYn M Mazama

a b e

Palaeosol E OrlhicRegosol Palaeosol F Orlhic Regosol

~r~

Tephra

Locationof radio-carbon-datedmaterials

Fig. 3. Schematic diagram of the Icefield Section, showing the sampled layers with horizon and profile designations, and dating control. Radiocarbon dates: (a) 1465 + 100 yr BP (BGS-634) from similar stratigraphic level in IF-80 (King, 1984); (b) 3370 3z 110 yr BP (Beta-4676, King, 1984); (c) 6170-4- 100 yr BP (GSC-2459, Bowyer, 1978 and this paper). Shard m o r p h o l o g y , particularly vesicularity and the presence o f inclusions, m a y help to distinguish tephras with different eruptive histories because it is related to the p r i m a r y characteristics o f the glass (Heiken, 1974) rather than resulting f r o m postdepositional weathering or alteration (Westgate and G o r t o n , 1981). We devised a

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235

Table 2 Selected physical and chemical data for samples from the Icefield Section Sample

Horizon

%Sand

%Silt

%Clay

%Total glass

pH

%Total carb.

Exch. Ca 2+

Exch. Mg 2+

C.E.C.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

Ahk Bhk IIAh IIBm llIAh IllBm~ IVBm2 VBh VIBm VIIAh VIIBm VIICk VIIIAh VIIIBm IXBm IXCkl IXCk 2

24,0 9.5 5,0 21,9 9.5 31.4 26,1 8,1 13.9 12.4 13.1 49.3 30.9 12.4 6.2 47.6 44.4

64.9 63.9 46.5 38.8 56.0 68.6 61.7 70.0 60.9 58.6 57.2 42.9 49.4 79.6 81.4 39.0 52.7

11.1 26.6 48.5 39.3 34.5 0.0 12.2 21.9 25.2 29.0 29.7 7.8 19.7 8.0 12.4 13.4 2.9

9.5 29.0 23.5 8.5 36.5 88.0 4.0 7.0 77.7 41.5 11.5 4.5 51.5 96.5 15.5 6.5 1.5

7.7 7.6 7.4 7.5 7.5 7.7 7.6 7.6 7.5 7.4 7.4 7.6 7.5 7.6 7.4 7.6 7.7

38.6 10.6 1.8 2.8 1.8 1.4 34.4 21.4 1.8 1.0 2.4 37.0 8.4 1.8 3.0 40.2 62.0

8.8 17.0 35.0 14.5 24.0 5.3 8.5 11.0 12.5 19.0 15.7 5.5 20.0 10.0 17.0 8.0 3.3

0.8 1.5 2.9 1.2 1.7 0.3 0.9 1.2 1.0 1.6 1.4 1.7 1.8 0.9 1.6 0.7 0.4

12.7 30.7 77.5 32.8 55.7 8.2 11.7 17.7 18.0 37.6 36.9 8.9 33.7 21.3 35.0 9.0 2.6

Particle sizes: Sand (2 m m - 6 3 #m), silt (63-2 #m), clay (< 2 #m). %Total glass, percentage of identifiable glass shards in subsamples from the 106-63 #m fraction; exchangeable cations, calcium and magnesium, in cmol kg-l; C.E.C., cation exchange capacity in cmol kg -1. Data from Bowyer (1978).

simple shard morphology classification scheme to aid in the identification of these tephras (Table 4). Clear glass shards form 48% of the identifiable glass in Mazama tephra (Sample 14) and often have a characteristic "Y" or curved shape, indicating formation by breaking of larger vesicles (Heiken, 1974). In contrast, Bridge River and St. Helens Yn tephras are vesicular; some vesicles may be elongated. Such "stretched" shards are particularly common in Bridge River tephra whereas St. Helens Yn tephra contains a greater amount of fine vesicular glass. This morphological analysis confirmed that Mazama tephra can be distinguished from the others based on shard morphology. Electron microprobe analysis of shards showed compositional variation between the tephras (Table 5). All shards consist predominantly of Si and A1 oxides but the relative proportion of minor constituents varies. Mazama glass contains slightly higher amounts of Na, Fe, and Ti oxides, whereas Bridge River glass contains slightly higher amounts of K20. St. Helens Yn glass is intermediate between Bridge River and Mazama in most components but does have the lowest amount of FeO. These values compare well with those of average glass composition for these tephras (Westgate and Gorton, 1981: Table 2). Because standard deviations overlap and no single element distinguishes clearly between tephras (Table 5), discriminant function analysis (DFA) was used to see if a combination of elements distinguished the glass types, using SPSSx Discriminant (SPSS Inc., 1988). Westgate and Gorton's (1981: Table 2) data for average glass

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236

Table 3 Additional chemical data for samples from the Icefield Section Sample Horizon OM% OC% TOC% Humus composition

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

Ahk 3.7 Bhk 8.8 IIAh 33.0 IIBm 6.4 IIIAh 19.8 IIIBml 1.9 IVBm2 3.8 VBh 6.1 VIBm 4.8 VIIAh 8.1 VIIBm 2.2 VIICk 1.0 VIIIAh 10.9 VIIIBm 3.0 IXBm 1.9 IXCk I 1.9 IXCk 2 1.0

0.7 1.2 5.9 1.2 2.9 0.5 0.4 0.8 0.8 1.6 0.8 0.4 2.2 0.6 0.3 0.3 0.2

0.6 2.5 8.1 1.4 3.9 0.5 4.5 0.6 0.8 1.7 0.7 0.3 2.5 0.8 0.3 0.5 0.4

Iron and aluminum fractions (%)

%H %F H/F %Fep (Fe+AI) d

(Fe+Al)o

(Fe+Al)p

0.6 0.1 2.0 0.5 1.7 0.4 0.1 0.6 0.6 0.8 0.5 0.2 1.3 0.4 0.2 0.1 0.1

0.8 0.3 1.2 1.1 1.2 0.7 0.6 1.0 1.4 1.4 0.8 0.6 1.2 1.8 1.0 0.7 0.2

0.2 0.2 0.6 0.4 0.6 0.1 0.3 0.3 0.5 0.4 0.4 0.2 0.3 0.2 0.2 0.1 0.0

0.0 2.4 6.0 0.9 2.3 0.1 4.3 0.0 0.2 0.9 0.2 0.2 1.2 0.5 0.3 0.3 0.3

0.1 0.02 0.1 0.34 0.4 0.55 0.2 0.75 0.3 0.40 0.0 0.33 0.2 0.1 2.66 0.2 0.83 0.2 2.57 0.2 0.75 0.1 1.08 0.1 0.81 0.1 0.84 0.1 0.36 0.1 0.19 0.0

0.6 1.0 1.1 1.3 1.2 0.2 0.9 1,1 1,1 1,3 1.4 0.8 0.8 0.6 1.3 0.8 0.3

OM%, percentage organic matter from modified Walkley-Black method (Sheldrick, 1984); OC%, organic carbon by sodium pyrophosphate extraction method (Bascomb, 1968); %TOC, percentage total organic carbon (humic+ fulvic carbon) from Kononova's method (1966); Humus composition, %H, percentage humic component, %F, percentage fulvic component, H/F, ratio of humic/fulvic components; (Fe + Al)d, citrate-dithionite-extractable (Fe + A1); (Fe + A1)o, oxalate-extractable (Fe + A1); Fep, pyrophosphate-extractable Fe.

Table 4 Morphological characteristics of glass shards for three tephra layers from the Icefield Section

BR SHY MAZ

CG

S

SV

FV

CV

O

NO

N

G

%G

5.7 11.7 48.2

2.8 2.0 9.8

20.5 4.6 8.9

16.5 55.8 3.1

54.6 26.0 30.1

3.0 9.0 0.5

4.5 14.0 3.0

200 200 200

176 154 193

88.0 77.0 96.5

Glass types: CG, clear glass; S, stretched; SV, stretched vesicular; FVS, fine vesicular stretched; FV, fine vesicular; CV, coarse vesicular. G, number of identifiable glass shards. Other grains: O, opaques; NO, nonopaques, non-glass. G, number of identifiable shards; %G, percentage of identified grains that are glass shards. Values of shard morphological categories expressed as a percentage of the identifiable glass shards. Other values expressed as percentages of total identifiable grains. BR, Bridge River, layer 6; SHY, St. Helens Yn, layer 9; M, Mazama, layer 14. Samples pretreated for removal of organic matter, secondary carbonates and iron oxide coatings. Fine sand fraction 125-63 #m.

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237

Table 5 Microprobe data for glass shards and magnetite grains from tephra samples from the Icefield Section BR

SHY

MAZ

2.30 4- 0,55 0.29 5:0.08 13.47 5:0.52 75.66 ± 1.10 3.025:0.04 1.19 5:0.11 0.27 ± 0.04 0.02 5:0.03 0.03 + 0.06 1.33 5:0.17 97.58 -4- 1.11 6

1.89 5:1.13 0.35 5:0.06 13.91 5:0.35 75.07 5:1.79 2.075:0.22 1.58 5:0.04 0.08 5:0.04 0.01 ± 0.01 0.02 5:0.04 1.18 5:0.11 96.18 5:2.05 6

3.07 5:0.31 0.42 5:0.15 14.36 5:0.34 72.58 5:1.63 2.51 5:0.11 1.38d: 0.07 0.41 5:0.06 0.01 5:0.02 0.05 5:0.06 1.87 ± 0.13 96.64 5:1.79 6

1.95 -4- 0.23 1.99 ± 0.28 34.88 5:0.44 53.91 5:1.64 7.31 5:0.61 0.48 + 0.04 0.03 4- 0.03 100.56 + 1.26 20

1.08 ± 0.12 2.58 5:0.36 34.82 5:0.87 54.88 5:2.08 5.85 5:1.11 0.32 5:0.05 0.02 + 0.02 99.55 ± 1.31 16

2.30 5:0.21 2.25 + 0.32 35.08 + 1.35 49.89 5:2.85 8.65 5:1.26 0.46 5:0.05 0.05 5:0.10 98.68 5:2.39 12

Glass shards Na20 MgO A1203 SiO 2 K20 CaO TiO z CrO 2 MnO 2 FeO

Total N

Magnetite grains MgO A1203 FeO a Fe203 a TiO2 MnO2 Cr203

Total N

N = Number of grains analyzed. Analyses carried out with a Materials Analysis Corporation Model 400 (modified) microprobe (Geology Department, University of Western Ontario). For microprobe operating standards and conditions see King et al. (1982). Mean and standard deviation for each component are given. BR, Bridge River, layer 6; SHY, St. Helens Yn, layer 9; M A Z , Mazama, layer 14. a Iron partitioned assuming stoichiometry.

composition of these tephras were used for comparison. The D F A revealed that eight variables were needed to distinguish between the three tephras based on glass composition (Table 6). Using two discriminant functions, all tephras, including those of Westgate and Gorton (1981), could be correctly assigned to their respective groups (Fig. 4). Electron microprobe analysis of titanomagnetites from the tephra layers showed clear differences between St. Helens Yn and the other tephras (Table 5). St. Helens Yn tephra titanomagnetites contain less TiO 2 than the other types, about 6% compared to about 7% for the Bridge River and about 9% for Mazama tephra (Table 5). Characteristically, Mazama tephra contains greater amounts of TiO 2 than the other tephras from this area (Westgate and Gorton, 1981). The titanomagnetite values obtained from these samples are similar to those from reference samples of these tephras provided by J.A. Westgate (Beaudoin and King, 1986). Multivariate statistical analysis (DFA) of magnetite data from these and other samples from the Sunwapta Pass area showed that Bridge River and Mazama tephras are often not

A.B. Beaudoin, R.H. King / Catena 22 (1994,) 227-248

238

Table 6 Discriminant function analysis on microprobe data from glass from three tephras from the Icefieid Section

Standardized canonical discriminant functions

Function 1 Function 2

MgO

A1203

SiO 2

K20

CaO

TiO 2

MnO 2

FeO

0.490 0.729

1.334 -0.377

-1.401 1.355

0.943 0.946

-1.333 -0.190

0.544 -0.474

-1.377 0.721

0.964 -0.142

Eigenvalue

Percent of variance

Canonical correlation

68.283 13.678

83.31 16.69

0.993 0.965

Functi'on 1 Function 2

Data taken from output produced by SPSS x Discriminant (SPSS Inc., 1988).

-80

-40

4.0 1

0.0

! [

80

Bridge River

8.0

8.0

g Z

!

[]

-: 40i "g

Z o

r'l

o~o o []

4.0

B

!

O0

,jo

o~

0.0

0 :~

-40

OM

.....

S 0

-4.0

g -8.0

Mazama

St Helens Yn

-80

ii!

T -8.0 Canonical

T~ -40

T

O0

4.0

discriminant

8.0

function

~r

Group centroid

Fig. 4. Scattergram showing groups produced by discriminant function analysis of microprobe data from glass shards of three tephras from the Icefield Section. The average tephra values of Westgate and Gorton (1981) are also plotted (M, S, and B respectively). Scattergram redrawn from output produced by SPSS x Discriminant (SPSS Inc., 1988).

A.B. Beaudoin, R.H. King / Catena 22 (1994) 227 248

239

clearly distinguishable based on magnetite composition alone, whereas St. Helens Yn is distinct (Beaudoin and King, 1986). 4.3. Soil characteristics

Parent material variations provide the primary criteria for differentiating the soils preserved in the section. The surface soil (Samples 1 and 2), characterized by moderate alkalinity, high carbonate content and low concentrations of illuvial Fe and A1, meets the criteria for an Orthic Melanic Brunisol according to the Canadian Soil Classification System (Fig. 3; ACECSS, 1987). Beneath this soil is another Orthic Eutric Brunisol with a significantly higher clay content and a markedly lower total carbonate concentration. Clay skins are absent in the B horizon (Table 1). This soil overlies a layer with very high concentrations of volcanic glass in the fine sand fraction, especially within the Bm I horizon. In contrast, the lower solum (Bm2) of this soil contains very low concentrations of volcanic glass and a high carbonate content, suggesting some parent material stratification. A radiocarbon date of 1,465 + 100 yr BP (BGS-634) on a lens of organic matter within this tephra layer in adjacent Section IF-80 indicates that this may be Bridge River tephra (Mathewes and Westgate, 1980). Beneath this soil is a dark coloured layer, probably an Ah horizon, too thin and discontinuous to be sampled, underlain by a Bh, Bm horizon sequence, typical of an Orthic Eutric Brunisol. The high volcanic glass concentration (78%) of the Bm horizon indicates that this is another tephra layer and a radiocarbon date of 3,370 + 110 yr BP (Beta-4676) on organic matter directly below confirms that it is likely St. Helens Yn tephra (Luckman et al., 1986). This tephra appears to have been deposited directly on top of a debris-flow, in which has developed a thin (4 cm) Bm overlying a coarser textured, strongly calcareous Ck. This soil is classified as an Orthic Regosol owing to its thin Bm. Immediately underlying the debris-flow is another Orthic Regosol, but formed on a volcanic ashfall. A radiocarbon age of 6, 170 + 100 yr BP (GSC-2459) on charcoal immediately above the tephra layer indicates that it is Mazama. This is underlain by a gravelly calcareous debris-flow in which has developed a weakly developed soil identified as an Orthic Regosol because of its incipient Bm horizon. Soil chemistry appears to be strongly influenced by the nature of the deposits, pH is relatively uniform throughout the section, ranging from pH 7.4 to 7.7. Carbonates, on the other hand, show marked concentration variations, being generally highest in the unaltered debris-flows. However, relatively high carbonate contents at the surface and at a depth of 45 to 66 cm suggest the effects of carbonate influx and reprecipitation. Cation exchange capacity is strongly related to clay and organic matter distributions, and the dominance of calcium and magnesium carbonates in the system is reflected in the dominant cations on the colloidal exchange sites. All samples from the Icefield Section contain measurable quantities of extractable forms of iron and aluminum generally considered to be of pedogenic significance (Table 3). Decalcification and leaching has not been sufficiently intense to facilitate the translocation of iron (Fep) in sufficient quantities to form Bf or Bhf horizons, in spite of the abundance of organic acids, in particular fulvic acid known to be a very

A.B. Beaudoin, R.H. King / Catena 22 (1994) 227-248

240

Table 7 Minerals identified by X-ray diffraction analysis of fine sand, silt, and clay fractions of samples from the Icefield Section Sample

Horizon

Fine sands (106-63 #m)

Silts (63-2 #m)

Clays (< 2 #m)

Qz

D1

PI

Qz

DI

P1 Ch

Ca

Mu

Qz Pl

Ch I1

Ve

Sm

X -

X -

X X X X X

X X X X X

X X X X Fe

X X X X X

X X X X X

?T

X

-

X

X

X

Fe

X

X

?T

X

X X X -

X X X X X X X X X X X

X T X X X X X X T X X

Fe X Fe Fe Fe Fe Fe Fe X X X

X X X X X X X T X X X

X X X X X X X X X X X

T T X X

X X X

T X ?T

X X X X

1

Ahk

X

X

X

XX

XX

X

2

Bhk

X

XX

X

XX

X

-

3 4 5

IIAh IIBm IIIAh

XX XX X

-

X

XX X XX

-

X

6

IIIBm 1

X

-

XX

X

-

7

IVBm 2

X

XX

-

8

VBh

X

X

X

9 10 11 12 13 14 15 16 17

VIBm

X

-

VIIAh VIIBm VIICk VIIIAh VIIIBm IXBm IXCkl IXCk 2

X X X XX X X X X

XX X X X XX

X X X X X -

XX XX XX XX XX XX XX X XX XX X

XX XX XX X XX

X X X X X

X

X

-

X

X

-

X X X X X -

X X X X X XX X

XX X

In

Interpretation of peaks from X-ray diffraction traces: XX, mineral present, peak is clear, intense and sharply defined; X, mineral present, peak clearly identified; T, mineral trace, peak identified; Fe, ironrich chlorite; - , mineral absent or peak not identified. Clay a m o u n t s are expressed qualitatively according to the relative peak intensities. Minerals identified from X-ray diffraction traces: Qz, quartz; Ch, chlorite; Ca, calcite; DI, dolomite; Mu, muscovite; P1, plagioclase; I1, illite; Ve, vermiculite; Sin, smectite; In, interstratified or poorly crystalline material. active

chelating

(Fe+A1)o, Mazama

are

agent. greater

tephra

second

seven

including

of (Fe+A1)d,

all three

with

the

may be removing

tephras,

greatest

values

value

of

in the

F e a n d A1 f r o m p r i m a r y

1972) or from volcanic glass (Parfitt and Childs, 1988). Supporting

explanation,

oxalate-extractable

King

(1986)

silica (SiO2) from

These data reflect the amorphous, a n a l y s i s ( T a b l e 7), p r o b a b l y tion of the amorphous St. H e l e n s

samples,

those

( T a b l e 3). T h e t e c h n i q u e

minerals (Pawluk, the

In than

considerable

non-crystalline

derived from weathering

clay component

Yn and Mazama

reported

the Mazama

tephras

using NaOH contained

tephra

amounts

(13.7%)

of

in the Icefield Section.

component

identified from XRD

of glass shards. Selective extracrevealed that the Bridge River,

270,48%

and 61%

respectively

of

Fig. 5. X-ray diffractograms for clay samples from Bhk, IIIBml (Bridge River tephra), IVBm (St. Helens Yn tephra), and VIIBm. Treatments: (a) M g saturated, air-dried; (b) M g saturated, glycolated; (c) K saturated, air-dried; (d) K saturated, heated to 300°C for 1 hour; (e) K saturated, heated to 550°C for one hour. Scan rate 2 ° 20/minute, count rate 2000 c.p.s., Ni-filtered Cu-K~ radiation, using General Electric XRD-5 diffractometer (Engineering Department, University of Western Ontario).

A.B. Beaudoin, R.H. King / Catena 22 (1994) 227 248

241

Sample 2 Bhk

Sample 6 IIIBml Bridge River

J ~ d

I

I 14.42A

10.04/~

7,13A ~

14.42 A

a

10.04A

7.13A 6.80A

I

I

I

L

I

I

I

I

I

I

I

~

4°

6°

8°

I0 °

12°

14°

4°

6°

8°

10°

12°

14°

Sample 11 VIIBm

Sample 9 IVBm St. Helens Yn

e

~ n 14.42 A

10.04 A

16.66 A 14.42 A

7.13A

I

I

i

I

6°

8°

10°

12°

14°

10.04 A

7.13A

i

I

I

I

I

I

4°

6°

8°

10°

12°

14° 2020

242

A.B. Beaudoin, R.H. King / Catena 22 (1994) 227-248

amorphous material, suggesting that the amount of amorphous material increases with increased age and weathering. In the Canadian Rockies, other studies (e.g., King, 1984, 1986) have suggested that volcanic glass weathers easily and may be involved in development of distinctive clay mineral assemblages.

4.4. Clay mineralogy All samples contain a chlorite-hydrous mica-vermiculite clay mineral suite (Table 7). Hydrous mica (illite) was identified by a broad asymmetric 10 .,~ peak, with a tail towards the low-angle side for Mg- and K-saturated samples (Reynolds, 1980). Vermiculite is usually distinguishedobY a clear 14 .& peak when Mg-saturated and glycolated, which collapses to a 10 A peak when K-saturated and heated (Barnhisel and Bertsch, 1989). In many samples, there is a well-defined 14.42 ,& peak; in some (e.g., Sample 11; Fig. 5) this peak intensifies during glycolation and the 10 ~, peak broadens on the low angle side with K-saturation and heating. These data suggest an aluminum hydroxy-interlayered form of vermiculite (Barnhisel and Bertsch, 1989). Examination of XRD traces following treatment with 6N HC1, confirmed the identification of iron-rich chlorite (Kodama and Oinuma, 1963). Smectite was identified by a peak around 15 ,& after Mg-saturation that expands to about 17 A after glycol solvation. Of the non-clay minerals, all samples contain quartz (3.34 ,~ and 4.26 A peaks) and plagioclase (peaks at 2.89 A, 2.19 A, and 1.79 A). Dolomite, probably derived from the local bedrock, is also found in some sands and silts (Table 7). The XRD traces from the relatively unweathered debris-flows (Samples 12 and 17) show sharp distinct peaks with no evidence of smectite or poorly crystalline material (Table 7; Fig. 6). For clays from the surface soil (Samples 1 and 2), the peaks are also sharp and distinct, suggesting that well-crystalline clay material is present (Fig. 5). These samples all contain the basic chlorite-hydrous mica-vermiculite suite of clay minerals with dolomite in the fine sand and silt fractions (Table 7). The mineral suite in Sample 17 is probably similar to that from unweathered bedrock. In contrast, the tephra layers and those adjacent to them contain poorly crystalline material and clay mineral suites significantly different to those in the debris-flows. The Mazama tephra layer (Sample 14) includes expanding clay minerals in addition to the hydrous mica-chlorite-vermiculite suite (Fig. 6). In the St. Helens Yn tephra (Layer 9), the XRD peaks are sharper and more distinct, suggesting the presence of better organized (more crystalline) clay material (Fig. 5). After glycolation, the 14 .& vermiculite peak becomes broader to the 15 A side, suggesting presence of some expanding clays although no characteristic smectite peak is present. A broad plateau appears between 10 A and 14 A after the heat treatments, suggesting presence of poorly crystalline or interstratified material, possibly aluminum hydroxy-interlayered vermiculite (Barnhisel and Bertsch, 1989). All peaks in XRD traces from Bridge River tephra (Sample 6) are subdued and indistinct, implying only minor amounts of well-crystalline clay material. Fig. 6. X-ray diffractograms for clay samples from VIIIBm (Mazama tephra), IXBm, IXCkl, IXCk 2. For treatments and scan conditions, see Fig. 5.

A.B. Beaudoin, R.H. King / Catena 22 (1994) 227-248

243

Sample ! 4 VIIIBm Mazama

17.66/~

14.4#*

10.04 .~

7.13A

..c

b

i

i

i

i

i

i

i

i

i

i

i

i

4°

6°

8o

I0 o

12 °

14 °

4°

6°

8°

10 °

12 °

14 °

19.19 .~ '

I

14.42 A

10.04 .&

[1/ ~,

-~ , -~ J I

Y- -

I

Sample 16

IXCkl

~

SamplelxCk217

7.13A

i

d

d

I

c

I

a 4o

i 6°

J 8°

i 10 °

i 12 °

i T4 °

~ 4°

14.42A J 6°

o

10.04 J, i 8°

i 10 °

7.13.~ L 12°

i 14 °

2°2e

244

A.B. Beaudoin, R.H. King / Catena 22 (1994) 227-248

Samples adjacent to the tephras layers have clay mineral suites characterized by expanding clay minerals (Table 7) that are probably influenced by weathering products from volcanic glass. Sample 4, separated from Bridge River tephra only by a thin charcoal layer (Sample 5), contains trace amounts of an expanding clay. Sample 5 contains interstratified or poorly crystalline material and Sample 10, below St. Helens Yn tephra, contains hydrous mica and some smectite. Interlayered vermiculite is present in Samples 10 and 11, as indicated by a broad plateau between 10 A and 14 A after heat treatments (Sample 11; Fig. 5). Sample 8, immediately above St. Helens Yn tephra, contains small amounts of expanding clay and Sample 13, above Mazama tephra, contains interstratified material. In Sample 15, beneath Mazama tephra, the hydrous mica peak is poorly defined, suggesting that mica degradation is occurring (Fig. 6). This layer is the only one in which feldspar is present in only trace amounts (Table 7), perhaps because this mineral has been degraded or altered during weathering. King (1986) suggested that smectite and interstratified vermiculite in tephras in the Canadian Rockies may have been formed by alteration of hydrous mica and chlorite with addition of Al-hydroxy ions produced by weathering of volcanic glass. The hydrous mica and chlorite may be present as detrital contaminants in tephras (King, 1986). These data support this interpretation because volcanic glass in the upper solum, particularly in Bridge River tephra, would be particularly affected by intense weathering.

5. Discussion

The ubiquitous presence of volcanic glass shards within the fine sand fraction of the deposits in the section suggests that the influence of tephric materials on the soil physical, chemical and mineralogical properties are not restricted to the primary tephra layers. Clearly, some reworking, redeposition and weathering of the tephras has taken place. Clay concentrations vary significantly within the section, but there is no evidence of clay skins (Table 1). This suggests that clay accumulation is the result of weathering in situ either of the tephras or carbonates of local origin. There is disagreement over the characteristics and intensity of the impact of tephra on pedogenesis and soil development in the Canadian Rockies. King and Brewster (1976, 1978; see also Limbird, 1984) suggested that tephra has enhanced pedogenesis, and particularly podzolization, in mountain environments. In contrast, Smith et al. (1983) could find no evidence that tephra had accelerated pedogenesis or enhanced podzolization in soils they examined in Sunwapta Pass. In particular, they demonstrated that iron (particularly Fep) in the podzolic Bhfhorizons of soils they examined could be explained both by weathering of the non-tephric aeolian veneer and selective enrichment which would occur despite any contribution from tephra. Sites investigated by King and Brewster (1976, 1978) contained tephra as distinct and discrete layers, whereas in the situation described by Smith et al. (1983) tephra was present as a component of the surficial silty deposit overlying till and not as discrete layers. Unlike the Icefield Section, soils examined by Smith et al. (1983) did not contain distinct stratigraphy associated with episodic sediment inputs. Therefore, some difo

A.B. Beaudoin, R.H. King / Catena 22 (1994) 227-248

245

ferences between these studies may arise from the different landscape settings controlling the relative intensity of pedogenic and geomorphic processes affecting the soils. A range of pedogenic expressions might be expected, depending on the landscape setting. Tephras, especially Mazama tephra, are often associated with palaeosols in Alberta. In particular, in the foothills and plains of southern Alberta there are widely-reported pre-Mazama palaeosols (Beke and Pawluk, 1971; Waters and Rutter, 1984; Valentine et al., 1987), which have been variously inferred to be associated with conditions either warmer and drier than present (Waters and Rutter, 1984) or cooler and moister than present (Reeves and Dormaar, 1972). Pennock and Vreeken (1986) investigated a series of Mazama-associated palaeosols in the southern Alberta foothills and concluded that soil development varied widely depending on landscape position, and hence landscape stability, of the soil. They also found that up to six post-Mazama palaeosols might develop depending on the thickness of aeolian deposits. Waters and Rutter (1984) found no evidence of major intervals of postMazama soil development until formation of the present profiles in the soils they examined, which were mainly from floodplains. In the Icefield Section, the pre-Mazama palaeosol (Palaeosol F) is not as welldefined or developed as those reported from the Alberta plains, probably due to its high carbonate content and because there was only a comparatively short interval for soil development before deposition of Mazama tephra. In addition, due to climatic severity at this high elevation site, pedogenesis would proceed more slowly than in the Alberta plains. The number and development of palaeosols at the Icefield Section is closely tied to the sequence of mineral inputs. On the alluvial fan surface, the stratigraphy is highly variable. For instance, at section IF-80, King (1984) did not find evidence of St. Helens Yn tephra and did not identify the same sequence of palaeosols. Thus the number of palaeosols and their degree of development varies across the fan. In addition, at the Icefield Section, the whole section is probably still influenced by contemporary pedogenesis. Although much of the soil stratigraphy may be attributed to episodic deposition rather than pedogenesis, the analytical data (Tables 2 and 3) confirm that pedogenesis has been active throughout the section. Underlying horizons have continued to be affected by leaching and pedogenic processes operating with greater intensity higher up the profile. Illuviation and decalcification are identifiable, though minor, processes. Much of the structure and texture within the horizons and variation down profile may be attributable to variable parent materials rather than pedogenesis, At each stage, pedogenesis had only a short time to operate before an influx of new parent material. Hence, the degree of profile development at each stage is limited. The presence of charcoal layers in the section suggests that pedogenesis was interrupted by occasional forest fires (Fig. 3). However, none of these fires was followed by massive debris-flows at this site. The reduced frequency of debris-flows in the upper part of the section correlates well with other palaeoenvironmental evidence showing early Holocene subalpine forest vegetation development (Beaudoin and King, 1990) that would have stabilized surficial sediments, reducing the likelihood of debris-flows.

246

A.B. Beaudoin, R.H. King / Catena 22 (1994) 227-248

6. Concluding statement T h e physical, chemical a n d m i n e r a l o g i c a l characteristics o f sediments f r o m the Icefield Section s h o w distinct p a t t e r n s linked to the c o m p o s i t i o n o f v a r i o u s m a t e r i a l inputs. The a n a l y t i c a l d a t a indicate that, a l t h o u g h pedogenesis has been active t h r o u g h the H o l o c e n e , it has n o t been sufficiently intense or p r o l o n g e d to e r a d i c a t e the distinctiveness o f v a r i o u s p a r e n t m a t e r i a l s a n d b u r i e d soils. D e p o s i t i o n a l events were followed by phases o f l a n d s c a p e stability that d i d n o t allow soil d e v e l o p m e n t b e y o n d R e g o s o l i c or Brunisolic stages. T h e r e f o r e this section, a l o n g with m a n y others in the C a n a d i a n Rockies, has a c o m p l e x origin. The sequence o f events inferred from the section's s t r a t i g r a p h y a c c o r d well with the H o l o c e n e p a l a e o e n v i r o n m e n t a l history o f the a r e a inferred f r o m pollen analysis.

Acknowledgements This research was p a r t l y s u p p o r t e d t h r o u g h an N S E R C o p e r a t i n g g r a n t to R . H . K . W e are grateful to P a r k s C a n a d a for p e r m i s s i o n to c o n d u c t fieldwork in J a s p e r N a t i o n a l Park. W e t h a n k the following p e o p l e for assistance: R.L. B a r n e t t ( D e p a r t m e n t o f G e o l o g y , University o f W e s t e r n O n t a r i o ) for m i c r o p r o b e analyses o f tephras, K a r i e H a r d i e ( A r c h a e o l o g i c a l Survey, P r o v i n c i a l M u s e u m o f A l b e r t a ) for p r o d u c i n g the p h o t o g r a p h , a n d G o r d o n Shields ( C a r t o g r a p h i c Section, G e o g r a p h y D e p a r t ment, U n i v e r s i t y o f W e s t e r n O n t a r i o ) for d r a f t i n g the figures.

References ACECSS (Agriculture Canada Expert Committee on Soil Survey), 1987. The Canadian System of Soil Classification, 2nd edition. Agriculture Canada Publication 1646. Ottawa, Ont., 164 pp. Atmospheric Environment Service, 1982. Canadian Climate Normals 1951-1980: Temperature and Precipitation. Environment Canada, Ottawa, Ont. Bacon, C.R., 1983. Eruptive history of Mount Mazama and Crater Lake Caldera, Cascade Range, U.S.A. J. Volcanol. Geotherm. Res., 18: 57-115. Barnhisel, R.J. and Bertsch, P.M., 1989. Chlorites and hydroxy-interlayered vermiculite and smectite. In: J.B. Dixon and S.B. Weed (Editors), Minerals in Soil Environments. Number I in Soil Science Society of America Book Series. Soil Science Society of America, Madison, WI, pp. 729-788. Bascomb, C.L., 1968. Distribution of pyrophosphate-extractable iron and organic carbon in soils of various groups. J. Soil Sci., 19: 251-268. Beaudoin, A.B. and King, R.H., 1986. Using discriminant function analysis to identify Holocene tephras based on magnetite composition: a case study from the Sunwapta Pass area, Jasper National Park. Can. J. Earth Sci., 23: 804-812. Beaudoin, A.B. and King, R.H., 1990. Late Quaternary vegetation history of Wilcox Pass, Jasper National Park, Alberta. Palaeogeogr. Palaeoclimatol. Palaeoecol., 80: 129-144. Beke, G.J. and Pawluk, S., 1971. The pedogenic significance of volcanic ash layers in the soils of an East Slopes (Alberta) watershed basin. Can. J. Earth Sci., 8:664 675. Bowyer, A., 1978. The Sunwapta Section: composition and development of a complex stratigraphic section from Sunwapta Pass, Jasper National Park. Unpublished M.Sc. dissertation. Department of Geography, University of Western Ontario, London, Ont., 164 pp.

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247

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