A Study of Two Soils Derived from Volcanic Ash In
A STUDY OF TWO SOILS DERIVED FROM VOLCANIC ASH
IN SOUTHWESTERN BRITISH COLUMBIA AND A REVIEW AND
DETERMINATION OF ASH DISTRIBUTION IN WESTERN CANADA
by
JAMES IAN SNEDDON
M.Sc. University of British Columbia, 1970
A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF
THE REQUIREMENTS FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY
in the Department
of
Soil Science
We accept this thesis as conforming to the
required standard
THE UNIVERSITY OF BRITISH COLUMBIA
November, 1973 /
In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study.
I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the Head of my Department or by his representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission.
Department of
The University of British Columbia Vancouver 8, Canada //
ABSTRACT
Four papers are presented in this thesis each one report• ing on studies relating to volcanic ash with special reference to soils.
The first paper reviews a) some of the phenomena relating to the ejection and deposition of ash that are important in interpreting the significance of its occurrence,
b) the significance of ash layers to workers in the Quaternary,
c) the techniques available for the characterization and recognition of tephra,
d) the literature on ash deposits
in western Canada and compiles the noted occurrences. In addition this paper presents the data from a study to determine the amount of ash retained by soils within and beyond the major areas of deposition indicated in the literature.
The presence of ash in soils was found to be widespread though the amounts present may be limited for identification purposes, in some cases.
The second paper describes two soils derived from Bridge
River volcanic ash and their underlying paleosols and presents selected physical and chemical analyses. The analyses indicate
that in the youthful soils studied the physical properties of
the ash soils are inherited from the parent material. The colloidal and chemical properties are initially imparted by
organic matter with some influence from ash weathering products especially aluminum. Shallow surface additions of volcanic ash iii to soils influence soil properties to varying degrees depending on pedogenic environment and depth of material. The third paper evaluates a number of methods that have been used to identify podzolic B horizons and the influence of surface additions of volcanic ash on the podzolic characteristics of soils. Pyrophosphate, pyrophosphate dithionite, citrate dithionite bicarbonate extractions, phosphate sorption capacity and pH-dependent cation exchange capacity determinations all highlighted the podzol B horizons while acid ammonium oxalate extractions and pH determined in NaF did not. The presence of surface additions of Bridge River ash may influence acid ammonium Oxalate or NaF criteria but it was not found to reduce the value of the other diagnostic criteria examined in this study.
The final paper studies the amorphous material and clay mineral characteristics of the two aforementioned soils and examines some of the methods of extraction and isolation of clay materials in soils. All of the chemical treatments applied to the soils were found to result in some dissolution of secondary and primary soil materials. The treatments used to extract amorphous materials indicated that the Si to Al ratios of extracted materials was greater than 2. As this value approaches 2 the formation of allophane and imogolite will take place. This situation is indicated as having taken place in isolated capillaries as evidenced by the limited occurrence of imogolite-like material. Chlorite is the dominant clay mineral in the ash soils and is believed to be the weathering product of primary biotite, horneblende and pyroxene. iv
TABLE OF CONTENTS
Page
INTRODUCTION 1
VOLCANIC ASH, ITS SIGNIFICANCE AND DISTRIBUTION IN
WESTERN CANADA .... 2
Introduction 2
The Significance of Ash Layers in Quaternary^
Studies 3
Post Eruption Transportation and Deposition .... 6
Methods of Ash Identification 8
The Sources and Distribution of Quaternary Volcanic
Ash in Canada 12
The Presence and Distribution of Ash in Soils ... 31
Conclusions 48
References 49
A STUDY OF TWO SOILS DERIVED FROM VOLCANIC ASH IN
SOUTHWEST BRITISH COLUMBIA . . » 61
Introduction 61
The Morphology and Environment of Two Volcanic Ash
Soils 63
Materials and Methods 74
Results and Discussion 75
Conclus ions 89
References 92
THE PODZOLIC CHARACTERISTICS OF TWO SOILS DERIVED FROM
VOLCANIC ASH IN SOUTHWEST BRITISH COLUMBIA 96
Introduction 96 Page
Materials and Methods 98
Results and Discussion 100
Conclusions 112
References 115 THE AMORPHOUS AND CRYSTALLINE WEATHERING PRODUCTS OF TWO SOILS DEVELOPED IN VOLCANIC ASH IN SOUTHWEST
BRITISH COLUMBIA 118 Introduction 118 Materials and Methods 121 Results and Discussion 124 Conclusions 143 References 145
SUMMARY 148 vi
LIST OF TABLES Table Page
I-l. Sets of eruptions of Mt. St. Helens .... 16
2. Mean chemical composition of white River
ash 21 3. The approximate locations of sites where
volcanic ash has been located and
references 24 4. Locations of sites where volcanic ash was located and gross composition of the light fractions of three size separations of the non-organic matter fraction 33
II - 1. Climatic records of stations adjacent to
the study sites ..... 70 1. Continued 71 2. Selected physical analyses of the study
sites 78 3. Selected chemical analyses of the study
sites 81
4. Exchange properties of the study sites . . 85
III - 1. Ratio of oxalate to pyrophosphate-dithionite
to citrate dithionite to 0.1M pyrophos•
phate extractable Fe, Al, Si and Mn . . . 99
2. Percent Fe and Al extracted by four methods
and phosphate sorption by three methods
on the fine earth fractions of the
study sites 102 vii
Table Page III - 3. Mn and Si extracted by the four methods used to extract Fe and Al 103 4. Correlation coefficients between the three methods of P sorption, Pi, P2 and P3 and other soil properties at the 1% level of significance in two ash soils and their underlying paleosols 105
4. Continued 106 5. Correlation coefficients between pH- dependent C.E.C. and other soil properties at the 1% level of signifi• cance in two ash soils and their under• lying paleosols 110 6. pH in NaF, pH-dependent C.E.C. and values derived from Fe and Al extractions by oxalate and pyrophosphate in two ash soils and their underlying paleosols . . Ill IV - 1. Amount of selected elements released by
hydrogen peroxide treatment of the fine earth fraction of the study sites . . . . 125
2. Composition of the amorphous materials in
the clay fraction and ratio of amorphous
material in the fine earth fraction to
content of silt and clay 126
3. Analysis of Bridge River tephra 129 viii
Table Page IV - 4. Parts per million of Si, Fe and Al extracted by various reagents used
in the isolation of clay fractions
of selected soil samples and soil materials 130 5. Percentage of clay (<2/u) and fine clay (<0.02yu) separated by alkali and
acid dispersion 131 6. Clay fraction components estimated from x-ray diffractograms 133 ix
LIST OF FIGURES Figure Page I-l. Quaternary volcanic vents in Canada and adjacent areas of the United States 13 2. Sites of ash observations presented in table 3 and minimum fallout areas of the major ashfalls identified to
date in western Canada 15 3. The location of sites where volcanic ash was found to be present in soils .... 32 II - 1. Location of study sites and adjacent climate stations 62 IV - 1. Flow sheet for separation of allophane and imogolite 122 2. I.R. spectra of amorphous Si and Al and of
the clay fraction of ground Bridge River pumice, the site 1 Ah and II Bfb
extracted after H202treatment A, alkali D and acid E dispersion 135 3. A, Imogolite-like material isolated from the Ah horizon at site 1; B, Single filament of imogolite-like material isolated from the IIBmb horizon at site 2 and characteristic of most imogolite like particles found in other horizons 137 X
Figure Page IV - 4. Halloysite like particles observed in the electronmicrograph of the acid dispersed fine clay fraction of the
site 2 IIBmb horizon 139 5. A, Gel like material associated with acid dispersed halloysite; B, Gel like material associated with acid dispersed IIBhfb material from site 1 140 ACKNOWLEDGEMENTS
The author wishes to express his sincere appreciation to Dr. L.M. Lavkulich of the Department of Soil Science for his assistance and encouragement throughout the project. Sincere appreciation is also extended to Mr. L. Farstad, Head of the British Columbia Soil Survey Section, Canada Agriculture for his interest in the project and for making available the facilities at his disposal.
Thanks are due to Dr. W.H. Mathews for reviewing the thesis and for his useful comments, to Dr. R.E. Carlyle for editing the thesis, to Dr. V.J. Krajina for the identification of some of the plant species encountered, to members of Canada Agriculture, Vancouver Soil Survey Section, the British Columbia Department of Agriculture Soil Survey Division, Dr. N. Keser, Mr. K. Klinka, Mr. R. Annas, Mr. E. Packee and Mr. M. Walmsley for providing soil samples and again to Mr. Walmsley for his help with the computer program.
To his wife Valerie the author extends his gratitude and appreciation for her understanding and cheerful encourage• ment during the course of this study. INTRODUCTION
The need for studies to identify the sources, distribu• tion and content of ash in soils in western Canada and to determine its influence on soil properties has been recognized for some time by pedologists. This study sets out to satisfy some of these needs in a series of four papers by, a) compiling the available information on the sources and distribution of ash in western Canada, b) determining the content of ash in soils within and beyond the major fallout paths determined to date, c) studying two soils developed in volcanic ash in southwest British Columbia and determining selected physical, chemical and mineralogical properties. From this information an indication of the influence of surface additions of volcanic ash on soils was obtained. VOLCANIC ASH, ITS SIGNIFICANCE AND DISTRIBUTION IN WESTERN CANADA
INTRODUCTION
Although recurrent and sporadic, the ejection and accumula• tion of tephra takes place over limited periods of geologic time. The more widespread and recognizable a deposited tephra layer, the more significant it becomes as a time stratigraphic and correlative marker to researchers in the Quaternary.
Volcanic ash is associated with most volcanic eruptions though the quantity varies from major to very minor amounts depending on the type of eruption. With one exception, the sources of the major Quaternary ash deposits so far determined in Canada, lie in Alaska or south of the 49th parallel. A number of ash deposits of limited distribution are associated with volcanic vents in British Columbia.
The usefulness of ash layers in Quaternary studies depends on an appreciation of the processes responsible for its vari• ability in composition, its distribution on the landscape and to a large extent on its positive identification. This paper reviews some of the areas of study that have made use of the presence of volcanic ash, the modes of ash deposition, some of the methods of identification, and the sources and distribution of Quaternary ash in Canada. In addition the results of an investigation to determine the 3 amounts of ash and its significance in soils and its geographi• cal extent are presented.
THE SIGNIFICANCE OF ASH LAYERS IN QUATERNARY STUDIES
The presence of a recognizable layer of volcanic ash within a deposit or on a surface has been used as a time stratigraphic marker for correlating widely separated occurrences. It also has been used as an indicator of the characteristics of the distributing medium. Based on bog and pedological studies in Iceland Thorarinsson (1943) concluded that, "owing to their, geologically speaking, momentary formation, their frequently very wide dispersal, their slight thickness and their characteristic appearance, volcanic ash layers fulfil every demand on good geological guide horizons." He proposed the term tephrochronology to designate a geological chronology based on the measuring, interconnecting, and dating of volcanic ash layers in soil profiles.
The uses of volcanic ash beds in geomorphic studies in New
Zealand have been reviewed by Pullar (1967). Elsewhere ash layers have been used in geomorphic studies related to alluvial, glacial, loessial, beach and organic deposits, weller (1960, pp. 173 and 542) indicated that in stratigraphic studies ash layers and their alteration products, though of variable importance, can provide a basis for correlation superior to that of fossils. 4
In south central British Columbia, Ryder (1970, p. 323, 1971) has found an ash layer useful as a time marker in assess• ing rates of postglacial fan sedimentation. The presence of ash in buried soil horizons was also used by van Ryswyk (1969) in the interpretation of solifluction processes in the Okanagan Range of the same area. Nasmith et al., (1967) determined the mean rate of accumulation of organic deposits by measuring the depths of accumulated organic material between dated tephra layers and the surface. In Germany ash layers have been used as a means of dating and correlating Rhine terraces (Fairbridge, 1968, p. 1132; Howard ejt al_., 1968, p. 1122). The presence and absence of ash in certain areas has provided useful informa• tion in assessing the position of continental ice margins (Westgate et ajL., 1970; Richmond, 1972; Fairbridge, 1968, p. 828). the chronology of neoglacial moraines (Miller, 1967) and in the interpretation of the geomorphic history of the landscape (Fryxell, 1972). Volcanic tephra on raised beaches in Arctic Canada provided Blake (1970) with a time line which served to correlate widely separated marine features of tilt and uplift. Ash deposits in ocean sediments have been used in the study of paleocirculation patterns in the North Atlantic (Ruddiman, 1972). They have also been used in developing the stratigraphic column and tracing the dispersal rates of postglacial sediments off the Washington and Oregon coasts (Griggs and Kulm, 1970; Nelson ejb al., 1968; Royse, 1967).
Archeologists have used pyroclastic materials to correlate archeologic sites and date prehistoric events by the indirect use of tephrochronology (Fryxell et al., 1968; Malde, 1969; 5 Reeves and Domaar, 1972; Sanger, 1967; and Steen-Mclntyre,
1969). Paleoclimatic interpretations have been aided by the presence of volcanic ash in polar ice (Gow and Williamson, 1971). Qualita• tive data on atmospheric conditions prevailing at the time of an eruption have been based on the interpretation of fallout paths of ash layers. Eaton (1964) also has interpreted the fallout paths of ash layers in presenting a possible independent approach to the problem of polar wandering.
Associated with paleoclimatic studies, palynological and paleoecological investigations have utilized the presence of volcanic ash layers in correlating widely separated sites and environments to the same period in time (Hansen, 1955; Heusser, 1960; Riggand Gould, 1957). The full potential of ash layers, in organic accumulations, has not been realized in the past due to the difficulty in recognizing thin layers in situ and in their positive identification and characterization.
In pedologic studies ash layers can provide a basis for the study and assessment of soil formation with time and in different weathering environments. By estimating the degree of soil development in a series of paleosols developed in ash parent material of known identity and age, Vucetich (1968) was able to infer the rate of soil development over the last 20,000 years on the North Island of New Zealand. In Costa Rica, Harris (1971) determined the sequence of development of podzol-like soils by similarly studying a number of paleosols developed in dated ash deposits. The effects of differing weathering environ• ments was determined by Bockheim et^al., (1969) in studies on 6
the B and C horizon of soils developed in a single ash layer. Volcanic ash soils have received the most attention in countries with large areas of ash derived soils such as New Zealand (Gibbs, 1968) and Japan (Japanese Government, 1964). In the Pacific Northwest and especially in Canada very few studies have been carried out on the pedogenic significance of volcanic ash.
POST ERUPTION TRANSPORTATION AND DEPOSITION
The pattern of ash distribution around a vent is determined by the wind direction prevailing at the time of the eruption. Wind direction and velocity may vary with altitude so that the distribution of ash ejected to great heights will reflect these variables (Eaton, 1964; Nayudu, 1964, p. 209). Wilcox (1959, pp. 435-441) gives an example from the literature of a bilateral distribution resulting from ash being carried to the east by winds below 20,000 feet and to the west by higher velocity winds above that height. The downwind distribution of ash from a vent ideally tends to be in the form of an elongate oval. Fallout patterns deviate from the ideal according to (a) altitudinal variations in wind speed, direction and turbu• lence, (b) changing wind directions during the course of an eruption, (c) the duration of an eruption and (d) the number of eruptions during the period of active volcanism (Bostock, 1952, pp. 37, 38; Fisher, 1964b; Macdonald, 1972, p. 137; Kaizuka, 1965). 7 Volcanic particles injected into the upper atmosphere are eventually distributed globally (Dyer, 1970? Flowers and Vie- brock, 1965). The presence of these atmospheric contaminants have been associated not only with unique cloud patterns and spectacular sunsets but also have been statistically correlated with world glacial advances, poor crop harvests, freezing of customarily ice free lakes and lower world temperatures (Bray, 1971; Coates, 1968, p. 356, Meinel and Meinel, 1963; Volz, 1964; Wexler, 1951; Gow and Williamson, 1971). Generally only minor modifications in world temperatures result from the presence of suspended volcanic particles in the atmosphere and these are relatively short term (Dyer and Hicks, 1965, 1968; Wexler, 1951).
The settling characteristics of airborn ash are a function of its size, shape and density. The external variables of air density, humidity, pressure, wind direction, velocity and turbulence are also significant (Eaton, 1964, p. 17; Fisher, 1964a, p. 341). The downwind settling of ash is subject to a winnowing action which results in a general decrease in bed thickness, decrease in particle size, improved sorting, decrease in heavy mineral composition and increase in the silica content of the ash (Eaton, 1964, pp. 19-23; Fisher, 1964; Nayudu, 1964, pp. 208-209; Scheidegger and Potter, 1968; Macdonald, 1972, pp. 140-141; Wilcox, 1959, pp. 434-435; Wilcox, 1965, p. 813). Exceptions to the downwind settling characteristics of ash, outlined above, are commonly encountered. These may be the result of changes in magma composition or variation in the explosive strength of an eruption sequence (Macdonald and 8 Abbott, 1970, p. 19; Wilcox, 1959, p. 429). Unexpected ash distribution patterns also may be the result of storm induced fallout of suspended ash (Okazaki e_t al., 1972, p. 82; Wilcox, 1965, p. 813).
On blanketing the landscape, ash is subject to erosion transportation and redeposition by wind, water, mass movement and to an extent ice (Eaton, 1964, p. 26; Segerstrom, 1950). Ash tends to be redeposited in areas of active sedimentation, and accumulation such as lakes, bogs, depressions, valley bottoms, alluvial fans and lee slopes (Ryder, 1970, pp. 313-324; Sneddon et al., 1972, p. 101; Wilcox, 1965, p. 812; Steen and Fryxell, 1965). Ash deposited on water may settle according to the aerial deposition pattern or be redistributed by currents and turbidity currents during sedimentation (Eaton, 1964, p. 27-29; Griggs and Kulm, 1970, pp. 1365-1375; Ruddiman, 1972; Nayudu, 1964, p. 199).
METHODS OF ASH IDENTIFICATION
The techniques for characterizing and identifying tephra layers have been developed to a high degree. However, as indicated by several workers (Randle et al., 1971; Czamanske and Porter, 1965; Steen and Fryxell, 1965) often no single approach is totally adequate without some accessory information. With increasing available information on the distribution and properties of ash layers in western Canada, the most appropri• ate methodologies can be selected, knowing the limitations of the techniques available and the complexity of the problem at 9 hand. Some of the limitations of various field and laboratory techniques have been reviewed by Wilcox (1965), westgate e_t al. (1970), and by Kohn (1970).
Wilcox (1965, p. 813) described factors to be considered in the recognition and sampling of ash in the field and Fryxell (1965) pointed out the significance of observation of strati• graphic and physiographic relationships.
Optical techniques have been widely used in the past. These involve the determination of the refractive index of the volcanic glass as well as identifying and characterizing the associated phenocrysts. In his review, Wilcox (1965, p. 813) cautioned that in certain environments post depositional changes in refractive index could occur. It has been established that chemical differences do take place in differing weathering environments (Bockheim et^ al., 1969; Gzamanske and Porter, 1965). However, Steen and Fryxell (1965) found no great altera• tion in the optical properties of ash, up to 12,000 years old, over the range of environments in their investigation. They did find, however, slightly lower (by 0.001) refractive indices in samples that had been chemically cleaned and a considerably lower index (by 0.006) in one sample from the A2 horizon of a spodosol.
Plots of the refractive indices of the natural versus the artificial glass, of the same ash, and ternary diagrams of mineral abundances were found to show useful relationships for distinguishing among ashes by Randle et al. (1971, pp. 276-281). The same authors also point out shortcomings in determining 10 mineral assemblages due to sorting, contamination and analyti• cal error. In ocean sediments off New Zealand, Donahue (1969) identified and correlated the distinctive mineralogy of different ash layers by means of cathodeluminescence. This is a relatively new tech• nique and may have a wider application. The elemental analyses of ash and constituent fractions of ash layers has been carried out by wet chemical analysis (Bock- heim et al., 1969), x-ray emission (Lerbekmo and Campbell, 1969;
McKenzie, 1970; Jack and Carmichael, 1969) emission spectrograph (Kohn, 1970), instrumental neutron activation analysis (Theisen et al., 1968; Randle et al., 1971) and electron microprobe analysis (Smith and Westgate, 1969; Westgate, 1972; Izett §_t al., 1970). Wet chemical analyses tend to be time consuming and leave a wide margin for experimental error. Instrumental methods of chemical analysis require relatively sophisticated equipment and some technical expertise for the most sensitive, operation and accurate results. X-ray emission and emission spectrographic techniques provide useful quantitative information. However, instrumental neutron activation analysis and electron micro• probe analysis have capabilities that are generally more useful and will be discussed later. The thermomagnetic properties of ferromagnetic minerals in tephra layers also have been shown to be helpful in distinguish• ing between similar or highly weathered ashes (Momose et al., 1968). 11 Neutron activation analysis is the most sensitive method for determining the greatest number of elements which increases the number of useful comparisons that can be made among samples. Randle §_t al., (1971) found on taking geochemical and other considerations into account that the best discriminators in their study were La, Th, Co and La/Yb ratios, while Rb, Cs, Ce and Ba could also be useful. Electron microprobe analysis is relatively rapid and is useful where a limited amount of sample is available. Only a few shards need to be analyzed to explore a range of composition for the comparison of materials (Izett et al., 1970). In addition, control is such that microlite and bubble inclusions in glass analyses can be avoided. Westgate et al. (1970) found that the determination of as few as three key elements, Ca, K and Fe or Ca, K and Na were sufficient to identify the sources of the ash layers in their study. The analyses of constituent fractions of bulk ash fractions eliminate some of the variability in results due to sorting, contamination, weathering and alteration. The glass fraction, separated by specific gravity methods, has proved to be useful for analysis (Theisen et al., 1968; Smith and Westgate, 1969; Izett et_ al., 1970). Some glasses may be unsuitable for certain analyses due to alteration or an abundance of voids and inclu• sions (Lerbekmo and Smith, 1972). Titanomagnetite and other similar opaque phenocrysts which are resistant to weathering and are readily separated have been found to be distinctive when present (Kohn, 1970; Westgate et al., 1970). 12 The relative age and inferred identity of volcanic ash layers can be determined by radiocarbon dating, given the occurrence of closely associated carbonaceous material. Though in some situations problems are associated with the technique (Healy et al., 1964, p. 7). Fission track dating has been successfully used to date Late Tertiary and Quaternary volcanic glass from Mount Edziza, British Columbia (Aumento and Souther, 1973). It appears to offer an accurate method of dating that can be applied to tephra provided certain criteria are met. Paleomagnetic, ionium and potassium-argon techniques are generally considered too imprecise for dating Quaternary materials (Damon, 1965; Kigoshi, 1967).
THE SOURCES AND DISTRIBUTION OF QUATERNARY VOLCANIC ASH IN CANADA
The Canadian Cordillera lies in a volcanic belt that has been active since early Tertiary times and continues to the present day, with the most recent activity taking place in Alaska. In Canada the latest activity, associated with the Aiyansh flow and cinder cone, took place 220 ± 130 radiocarbon years ago (Sutherland-Brown, 1969). Centres of Quaternary volcanism in Canada and adjacent areas of the United States are indicated in Figure 1.
All but one of the more extensive ash layers so far determined in Canada has originated in the united states, though a number of vents associated with limited amounts of ash do occur in western Canada. 13
Figure 1. Quaternary volcanic vents in Canada and adjacent areas of the United States. The triangles represent sources and probable
sources of ash found in western Canada. Adapted from Souther
(1970a, Fig. 8) and Wilcox (1965, Fig. 1). 14
The most extensive ash deposit, so far determined, in southwestern Canada originated from the eruption of Mount Mazama about 6,600 years ago. It has been estimated that up to 62.5 km3 (Williams, 1969, p. 49) of tephra were ejected and distributed to the north and east over a minimum of 900,000 km2 (Fryxell, 1965) in a series of eruptions. The fall-out paths of ash layers from Glacier Peak, Mount St. Helens, the Bridge River area and a number of layers of more limited extent fall within the depositional area of this ash in Canada (see Figure 2).
Plagioclase, augite, orthopyroxene, horneblende, magnetite, ilmenite and apatite make up the phenocryst suite of Mazama ash and the glass fraction has a refractive index from 1.494 to 1.505 (Westgate et al., 1970).
Smith and Westgate (1969) and Westgate et a_l., (1970) have carried out a number of analyses by electron microprobe of the glass, magnetite and ilmenite fractions of Mazama and other ash deposits found in Canada. Their published data identify some of the unique characteristics that separate the different ashes. Randle et al., (1971) determined certain identifying chemical characteristics of Mazama and other ashes by instrumental neutron activation analysis. Unique petrographic relationships of the same ashes also were presented which further aided in their characterization. Harward and Borchardt (1969) presented and compiled data on the mineralogy and elemental analyses of some ash deposits in the Pacific Northwest. They show some of the differences between Mazama and other ashes and variability due to distance from source and weathering environment. 15
Figure 2. Sites of ash observations presented in Table 3 and minimum fallout areas of the major ashfalls identified to date in western Canada. Fallout areas adapted from Bostock (1952, Fig. 1), Lerbekmo and Campbell (1969, Fig. h) , Okazaki et_ aj_. (1972, Figs. 1 and 2) and Westgate e_t _1_. (1970, Figs, k, 5, 6 and 7). 16 Mount St. Helens has erupted more than 40 voluminous pumice deposits in the last 35,000 years. These eruptions can be grouped into 7 sets, each with a characteristic Fe-Mg pheno- cryst suite (Mullineaux et: aJU, 1972).
TABLE 1 SETS OF ERUPTIONS OF MT. ST. HELENS (MULLINEAUX, ET AL., 1972)
Set Approximate age Prominent Fe-Mg minerals Distribution
T 150-200 hypersthene, hornblende, NE augite W 450 hypersthene, hornblende NE to S P 3,000-2,000 hypersthene, hornblende NE to E Y 4,000-3,000 cummingtonite, hornblende NE to SE J 12,000-8,000 hypersthene, hornblende NE to SE S 18,000- 12,000 cummingtonite, hornblende NE to E Unnamed 35,000-18,000 cummingtonite, hornblende, E to S biotite
One of the set Y layers, between 3,200 and 3,500 years old (Fulton, 1971? Westgate et aJL_., 1969), has been traced as a narrow NNE trending lobe into southern Alberta (see Fig. 2). The glass fraction of the ash has a refractive index of 1.494 to 1.510. The absence of pyroxene and the presence of cumming• tonite in the phenocryst suite of this ash readily distinguishes, it from others in its fallout path in Canada. Westgate e_t al., (1970) found in their electron microprobe analyses that the relatively high Ca and low K concentrations in the glass fraction were most diagnostic compared to glasses from other volcanoes encountered in the same fallout path. A relatively low MgO content in the magnetite and ilmenite compared to the other ashes is apparent in a limited number of analyses by the same authors. 17 Okazaki et al., (1972) correlated the NE trending 150 to 200 year old St. Helens T ash with the West Blacktail Ash, of Smith et al., (1968). They traced this ash to the 49th parallel (see Fig. 2) and anticipate its presence in Canada (Okazaki, personal communication). Layer T is distinguished, mineralog- ically, from the other St. Helens sets by the presence of augite as well as hornblende and hypersthene. The refractive index of the glass is between 1.497 and 1.501 and that of the augite and hypersthene 1.700. A sample of pumice thought to represent layer T was examined pet©graphically and by neutron activation analysis by Randle et al_., (1971). It was found to have a number of unique properties that readily distinguished it from the other ashes studied and from Mazama ash with which it might be associated in Canada. An unidentified ash layer underlying the West Blacktail ash has been collected on both sides of the 49th parallel between 114° and 121° longitude (Okazaki et al., 1972). No further details have been published on this ash though it is mineralog- ically different from the West Blacktail ash and is believed to be relatively young (Okazaki, personal communication). A thin layer of ash, less than 1220 ± 130 years old and with similar petrographic properties to St. Helens w ash, is widespread in South Central British Columbia (Fulton, 1971, p. 19). This may be part of the ash layer underlying the West Blacktail ash referred to by Okazaki et al., (1972). Petro- graphically, the St. Helens W ash is distinguished by the relatively low range of refractive index, 1.491 - 1.496, of the glass fraction, the relatively high range of refractive 18
index, 1.703 - 1.709, of the orthopyroxene, the phenocryst content consisting of abundant orthopyroxene with plagioclase, hornblende and magnetite and lack of clinopyroxene and cumming- tonite (Nasmith et al., 1967).
Activity at Glacier Peak about 12,000 years ago (Powers and Wilcox, 1964) resulted in the deposition of two closely spaced tephra deposits (Wilcox, 1969). Westgate et al., (1970) established a composite fallout path for both layers (see Fig. 2) based on the identification of one of the layers in southern Alberta. Neither of these ashes have been identified in British Columbia but it is likely that Glacier Peak Ash if present would mark the position of the receding Cordilleran Ice Sheet that covered much of the area at that time. Okazaki et al., (1972) showed the occurrence of a Glacier Peak-like ash up to the Canadian Border though they do not establish its source. Petrographically, the two layers are similar and can be distinguished from overlying St. Helens layers by the absence of augite and cummingtonite. Mazama ash differs in the higher indices of refraction of its glass and hornblendes compared to the phenocryst-rich Glacier Peak ash (Powers and Wilcox, 1964). The differences in the chemical composition of the glass and magnetite fractions of the ash also were found to be distinct by Westgate et al., (1970).
Steam eruptions on Mount Rainier have been recorded between 1820 and 1894 and a significant amount of ash was erupted about 600 years ago (Easterbrook and Rahm, 1970). An ash layer less than 2.5 cm thick and with similar mineralogical properties to the over 8,750 year old pyroclastic layer R of Mount Rainer 19
(Crandell et al., 1962) has been identified in the Boulder Valley of Mount Baker, about 25 km south of the 49th parallel (Burke, 1972).
Volcanic activity on Mount Baker has been recorded from 1792 to 1969. Ash eruptions were recorded in 1843 and 1854 (Easterbrook and Rahm, 1970). Burke (1972) identified aa ash unit up to 25 cm thick and older than the Mount Rainier R type ash in the Boulder Valley, of Mount Baker (referred to above). It is comprised of clinopyroxene, orthopyroxene, plagioclase and some amphibole phenocrysts and the glass has a refractive index of 1.51 to 1.53. The ash is assumed to have originated from Mount Baker. Outside of the Boulder Valley the distribu• tion of this ash is not known though it is possible that the fallout path lies across part of southern British Columbia.
An eruption source close to Plinth Mountain in the Lillooet River Valley of British Columbia gave rise to the Bridge River ash, about 2,440 years ago. The pattern of fallout extends east-northeasterly in a relatively narrow plume into western Alberta (see Fig. 2). Nasmith et al. (1967) summarized earlier information on this ash and indicated its distribution and possible source, westgate et al_. (1970) established chemical differences in samples of this ash from different locations and concluded that this was due to fractional crystallization of the parent magma during the course of the eruption.
Petrographically this ash is distinguished by the occurrence of 'spongy' or 'worm eaten' plagioclase, clinopyroxene, ortho- pyroxene and by the presence of biotite. Other phenocrysts present include magnetite and hornblende. The refractive index 20 of the glass is 1.494 to 1.505. Selected elemental combinations and abundances in the glass, titanium and magnetite fractions of the ash are distinctive when comparing Bridge River ash to other associated ashes (Smith and westgate, 1969; westgate et a_l., 1970). Volcanic ash believed to be from the vicinity of Mount Edgecumbe in southeastern Alaska, though the source is not verified, has been dated provisionally at between 9,000 years (Heusser, 1960, p. 184) and 11,000 years B.P. (McKenzie, 1970). Heusser (1960) indicated the possible distribution of the ash (see Fig. 2) based on his studies of peat bogs in the area. The extent of the ash and the depth of the accumulation in the Glacier Bay region strongly suggests that this ash may be found in adjacent areas of Canada. Some of the characteristics of the ash from Glacier Bay National Monument were determined by McKenzie (1970). Pheno• crysts made up 10% of the 250 mesh fraction of the ash and included pyroxenes, amphiboles, biotite, albite and potassium- feldspar. The glass fraction had a refractive index of about 1.51 and the ash had a specific gravity of 2.44 g per cc. Partial elemental analysis by x-ray fluorescence was carried out on the glass fraction of the ash. The weight percent of elements determined were: calcium, 2.0; iron, 2.85; manganese, 0.077; potassium, 1.64; titanium, 0.176; and zirconium, 0.142.
The White River ash consists of an estimated 25.4 km3 of
tephra distributed over an area of at least 234,000 km2 (Berger, 1960) and covers much of the southern Yukon and extends into the Northwest Territories and northern British Columbia (see Fig. 2). The bilobate distribution is the result of two relatively closely spaced eruptions that took place within the last 2,000 years and have been traced to a source beside the Klutlan Glacier in eastern Alaska (Lerbekmo and Campbell, 1969). Brooks (1899, pp. 365-366) first suspected two events had taken place. Since then evidence has been gathered to indicate that two events did take place and that the eastern lobe is about 1,220 years old and the western lobe is about 1,850 to 1,900 years old (Rampton, 1972, p. 20). Lerbekmo and Campbell (1969) determined the petrographic and chemical composition of the ash. The ash is rhyodacitic and is composed of plagioclase, horn• blende, hypersthene, magnetite and ilmenite phenocrysts. The glass has a refractive index of 1.502 - 0.002. The chemical composition of the ash determined by x-ray fluorescence as taken from the above authors' paper is shown in Table 2.
TABLE 2
MEAN CHEMICAL COMPOSITION OF WHITE RIVER ASH (66 SAMPLES) (LERBEKMO AND CAMPBELL, 1969)
Component Weight % PPM
36 sio2 67.4 Rb
A1203 15.1 Sr 771
Ti02 0.5 MgO 2.0 K/Rb 577 FeO 2.0 Ca/Sr 37
Fe 2.2 2°3
Na20 4.1
K20 2.5 CaO 4.1 22
Lerbektno and Smith (1972) found that, though the two lobes are mineralogically similar, electron microprobe analysis of the ilmenite fractions showed distinct differences. The extensive volcanic activity that has taken place in Alaska has undoubtedly contributed minor amounts of ash to parts of western Canada. Mount Wrange11 in eastern Alaska (see Fig. 1) is still active and occasionally erupts steam and ash (Black, 1958). The eruption of Mount Katmai in 1912 resulted in fine ash associated with acidic aerosols or precipitates falling in Dawson, Yukon Territory, Prince Rupert, Victoria and Vancouver, B.C., as well as in Port Townsend, Washington State (Records of B.C. Provincial Archives). Though widespread, none of this ash has been detected in relatively detailed studies of bogs from southeast Alaska to Vancouver Island and the Lower Mainland of British Columbia (Heusser, 1952; Hansen, 1950b; Kiss, 1961; Rigg and Richardson, 1938). This suggests that the fine materials from this eruption have been weathered relatively rapidly.
Apart from the major sources of volcanic tephra discussed above, there are over 140 Quaternary volcanoes in western Canada some of which are associated with tuff cinder and ash deposits (Souther, 1970a; Holland, 1964; Hanson, 1934). Possibly the most active area of Quaternary volcanism in Canada has taken place in the belt stretching from north of Prince Rupert to the southern Yukon. The major amount of activity being centered around the Mount Edziza - Spectrum Range area which has been active since late Eocene or early Miocene time (Souther, 1970a,b). Souther (1970a,b) indicates that early Pleistocene volcanism in this same area must have covered thousands of 23 square miles with airfall tephra and the most recent activity, less than 1,300 years ago, on Mount Edziza covered over 77 km^ with from 10 to 1 foot of tephra. Further investigation will no doubt extend the area of recognizable deposits of this material. Minor post Pleistocene deposits of ash are associated with eruptions in the Unuk River area (Wright, 1905), the Hogem Range, at Nazko (Holland, 1964) and in Garibaldi Park (Mathews, 1952, 1958). A number of glacial and interglacial deposits have been located in the Yukon and in southern British Columbia (Fulton, 1971; Smith, 1969; Westgate, 1972). However little information is available on these deposits. Westgate (1970) has described the wascana Creek ash in Saskatchewan derived from the Yellowstone Park area, Wyoming, and also indicated (Westgate, 1972) the presence of a number of other subtill pyroclastic layers in Alberta and Saskatchewan. Again, little published information is available on these materials.
Under suitable conditions offshore volcanism could result in ash being deposited on land. Herzer (1971) in studying a seamount of the Pratt walker chain found ash to be relatively widespread. No evidence has been found, to date, of this type of ash on land in Canada.
A considerable number of references to the presence of volcanic ash have been made in the literature and additional observations have been made by individuals in the field. The
sites of these references and observations have been plotted
on Fig. 2 and the latitude and longitude of the sites have been
tabulated in Table 3 with the appropriate references. 24
Table 3
The approximate locations of sites where volcanic ash has been
located and references
Lati tude Long i tude3 Source'3 References N W
48° 27' 123° 29' Mazama Lowden, J.A. & Blake, W., Jr. (1970) 48° 27' 123° 29' 11 Fulton, R.J. (1971) p. 21 48° 27' 123° 32' - Hansen, H.P. (1949a) 48° 3 V 123° 35' - Heusser, C.J. (I960) p. 105 kS° 02' 113° 23' - Horberg, L. (1954) 02' 119° 38' - Ryder, J.M. Pers. comm. 49° 03' 119° 3 V Mazama? Ryder, J.M. Pers. comm. k3° 03' 120° 09' Mazama Van Ryswyk, A.L. (1969) k3° 04' 119° 40' Mazama? Ryder, J.M. Pers. comm. hs° 05' 119° 38' - II II 49° 06' 119° 2,2' Mazama? II II ks° 06' 119° 42' 11 II II ks° 07' 119° 11 ' 2 layers Lewis, T. Pers. comm. kS° 08' 119° 42' Mazama? Ryder, J.M. Pers. comm. ks° 1 1 1 112° 58' - Horberg, L. (1954) k3° 12' 113° 06' - Horberg, L. & Robie, R.A. (1955) ks° 12' 122° 50' - Hansen, H.P. (1940) k3° 13' 119° 44' Mazama? Ryder, J.M. Pers. comm. 11 kS° 14' 119° 54' n II hS° 15' 113° 02' - Horberg, L. S Robie, R.A. (1955) k3° 15' 117° 49' 2 layers Lowden, J.A. S Blake, W.,Jr . (1970) ks° 15' 120° 50' - Lewis, T. Pers. comm. ks° 15' 122° 57' Mazama? Dyck, W. et al. (1966) p. 110 49° 15' 122° 57' Mazama Fulton, R.J.T1971) P- 21 k3° 16' 11;3° 05' - Horberg, L. (1954) 49° 17' 119° 48' Mazama? Ryder, J.M. Pers. comm. 11 k3° 17' 120° 04' n II ks° 17' 120° 35' 11 II II k3° 18' 113° 03' - Horberg, L. & Robie, R.A. (1955) hs° 18' 113° 34' - Dyck, W. et aj_. (1965) p. 31 49° 18' 122° 33' Mazama? Klinka, K., Pers. comm. 49° 18' 122° 34' 11 n II ks° 19' 122° 33' 11 II II 49° 20' 117° 52' 11 Dyck, W. et al. (1965) p. 31 ks° 20' 117° 52' Mazama Fulton, R.J.T1971) p. 21 49° 20' 122° 34' Mazama? Klinka, K. Pers. comm. 49° 20' 122° 35' Mazama n 11 1 49° 21 117° 45' - Lowden, J.A. et aj_. (1970p . 293 a Approximate locations,as many taken from figures, b ? Tentatively identified. - Not identified. 25
49° 21 ' 122° 33' Mazama? Klinka, K. Pers. comm. ks° 211 124° 35' - Hansen, H.P. (1949a) 49° 22' 122° 33' Mazama? Klinka, K. Pers. comm. 49° 23' 110° 42' Glacier Westgate, J.A. (1968) Peak 49° 24- 123° 11 ' Ma zama Brooke, R.C. (1965) 49° 28' 110° 34' - Stuiver, M. (1969) PP- 556-558. 49° 28' 113° 56' - Horberg, L. & Robie, R.A. (1955) 49° 28' 113° 58' - Horberg, L. (1954) 49° 29' 121 0 24' Ma zama? Mathewes, R.W. et a_l_. (1972) 11 11 11 49° 29. 121° 26' z,9° 30' 1 18° 05' 2 layers Lowden, J.A. S Blake, W., Jr. (1970) 49° 32' 112° 56' - Dyck, W. S Fyles, J.G. (1964) p. 170 49° 32' 114° 02' - Stalker, A.M. (1963) 49° 33' 121 0 24' Mazama? Lowden, J.A. et al. (1969) 49° 33, 121° 24' - McCallum, K.J. & Dyck, W. (i960) p. 78 49° 40' 120° 34' - Hansen, H.P. (1955) 49° 46' 113° 02" - Horberg, L. (1952) 49° 46' 113° 02' - Horberg, L. & Robie, R.A. (1955) 49° 46' 113° 57' Mazama? Horberg, L. (1954) 49° 46' 120! 27' St. Helens Y Nasmith, H. et al. (1967) 49° 46' 123° 02' Mazama Brooke, R.C.~Tl9T5) 49° 48' 114° 07' - Dyck, W. S Fyles, J.G. (1964) p. 170 49° 48' 122° 59' Mazama Brooke, R.C. (1965) 49° 51 1 123° 00' Local source Mathews, W.H. (1952) 1 h3° 51 123° 03' 11 n 11 n 49° 51 1 125° 12' - Hansen, H.P. (1949a) 49° 52' 114° 22' Mazama Reeves, B.O.K., & Domaar, J.F. (1972) 49° 53' 120° 37' St. Helens Y Fulton, R.J. (1971) p. 21 49° 53' 120° 37' St. Helens Y ? Dyck, W. et al. (1966) p. 110 49° 57' 116° 51' St. Helens W ? Fulton, R.J. (1970 p. 21 49° 57' 116° 511 11 11 Lowden, J.A. £ Blake W., Jr. (1970) 49. - p • /u 50° 06' 117° Lowden, J.A. et al. (1971) p. 293 50° 081 110° 34' Mazama? Lowden, J.A. et al. (1971) p. 287 50° 08' 110° 38' - Stalker, A.M.Tl96"9) 50° 09' 113° 59' - Dyck, W. et_ a]_. (1965) p. 31 50° 13' 121° 03' Mazama? Ryder, J.M. Pers. comm. 50° 14' 119° 01 1 Ma zama? Lowden, J.A. £ Blake, W., Jr. (1970) „ -7/5 p. II- 50° 15' 116° 59' Pre-Fraser Fulton, R.J. (1968), (1971) p. 21 Glaciation 50° 15' 116° 59' - Lowden, J.A. & Blake, W., Jr. (1968) p. 224 50° 15' 118° 38' Pre-Fraser Smith, G.W. (1969) pp. 51-65 Glaciation 50° 15' 118° 47' - Lowden, J.A. & Blake, W., Jr. (1970) p. 72 50° 18' 118° 52' Pre-Fraser Smith, G.W. (1969) pp. 51-65 Glaciation 50° 18' 121° 08' Mazama Ryder, J.M. Pers. comm. 50° 19' 112° 53' Mazama? Dyck, W. et_aj_. (1966) p. 108 26
50° 20' 121° 24' Mazama? Lowden, J.A. et_ aj_. (1969) Armstrong, J.E. & Fulton, R.J. (1965) p. 103 50° 21 ' 128° 21 ' Post Dolmage, V. (1924) Pleistocene 50° 22' 121° 22' Mazama? Ryder, J.M. Pers. comm. 50° 22 1 121° 24' Mazama Hal stead, E.C. S Fulton, R.J. (1972)
p. Z 1 50° 23' 119° 17' Mazama? Dyck, W. et al. (1965) p. 33 50° 23 ' 119° 17' Ma zama Fulton, R.J.T1970 p. 21 50° 23' 121° 16' 11 Hal stead, E.C. & Fulton, R.J. (1972) p. 23 50° 26' 119° 27' Pre-Fraser Lowden, J.A. et_aj_. (1967) p. 172 Glac iation 50° 26' 119° 49' - Hansen, H.P. (1955) 50° 26' 121° 04' Ma zama? Ryder, J.M. Pers. comm. 50° 28' 121° 21 1 11 50° 29' 119° kS' Mazama & St. Halstead, E.C. & Fulton, R.J. (1972) Helens Y p. 30 50° 29' 119° 51' St. Helens Y Nasmith, H. e_t aJL (1967) 50° 32' 104° 55' Waskana Creek Christiansen, E.A. (1961) 50° 32' 119° 45' 2 layers Lowden, J.A. et al. (1967) p. 172 50° 33' 104° 51' Waskana Creek Christiansen, E.A. (1961) 50° 3 V 121° 15' - Ryder, J.M. Pers. comm. 50° 36' 118° A3' - Lowden, J.A. S Blake, W., Jr. (1970) p. 72 50° 37' 119° 57' St. Helens Y Nasmith, H. et_ ajk (1967) 50° 37* 120° 11 1 Ma zama? Ryder, J.M. Pers. comm. 50° 37' 120° 11 ' St. Helens Y ? n 11 n 11 50° 37' 121° 19' Mazama? 50° 39" 120° ir St. Helens Y Halstead, E.C. & Fulton, R.J. (1972) p. 29 50° 39' 126° 26' Post Pleistocene Dolmage, V. (1924) 50° 40' 107° 54' - Stalker, A.M. (1970 50° 40' 120° 09' Ma zama? Ryder, J.M. Pers. comm. ~n 11 50° 40' 120° 07' St. Helens Y ? 50° 40' 120° 20' Pre-Fraser Armstrong, J.E. & Fulton, R.J. (1965) Glaciation p. 99 50° 411 119° 49' Mazama & St. Halstead, E.C. S Fulton, R.J. (1972) Helens Y p. 30 50° ' 119° 51" St. Helens Y Dyck, W. et al. (1966) p. 110 II II 50° 41' 119° 51' Fulton, R.J.T197D p. 21 50° 41' 120° OV St. Helens Y ? Ryder, J.M. Pers. comm. 50° 41' 120° 211 Mazama ? n 11 50° 41' 123° 22' Bridge River Nasmith, H. et_a]_. (1967) 50° 42' 120° 08' St. Helens ? Ryder, J.M. Pers. comm. 50° 42' 120° 14 II n n 11 50° 42' 120° 27' 1nterglac ia1 Halstead, E.C. & Fulton, R.J. (1972) p. 29 50° 44' 127° 25' - Heusser, C.J. (I960) p. 105 50° 47' 121° 08' Ma zama? Ryder, J.M. Pers. comm. II n 11 50° 47' 121° 13' 11 11 n 50° 47' 121° 20' 50° kS' 121° 23' 11 11 11 27
50° 51' 109° 57' Mazama David, P.P. (1970) 50° 52' 121° 24' Mazama? Ryder, J.M. Pers. comm. 50° 53' 121° 25' II II 50° 53' 122° 19' Bridge River Nasmith, H. e_t aj_. (1967) 50° 54' 121° 22' Mazama? Ryder, J.M. Pers. comm. 50° 54' 121° 22' 11 n II 50° 54' 122° 53' Bridge River Nasmith, H. e_t aj_. (1967) 50° 55' 121° 23* Mazama? Ryder, J.M. Pers. comm. 50° 55' 122° 11 ' Bridge River Nasmith, H. et al. (1967) II II 50° 55' 122° 28' II n 50° 56' 122° 37' n II II n 50° 57' 121° 25' Mazama? Ryder, J.M. Pers. comm. 50° 57' 122° 45' Bridge River Nasmi th, H. et al. (1967) 50° 58' 115° 10' Mazama Beke, G.J. S Pawluk, S. (1970 51° 00' 122° 56' Bridge River Nasmith, H. et aj_. (1967) 51° 02' 114° 05' Mazama? Lowden, J.A. et al. (1971) p. 290 51° 03' 121° 33* Bridge River Nasmith, H. et al. (1967) 51° 04' 118° 04' Mazama Fulton, R.J.T197D p. 21 51° 04' 118° 04' Ma zama? Lowden, J.A. et_ a_J_. (1970 51° 05' 121° 59' 11 Lowden, J.A. & Blake, W., Jr. (1968) p. 227 51° 05' 121° 59' Bridge River Lowden, J.A. & Blake, W., Jr. (1968) p. 227 51° 10' 121° 53' II n Nasmith, H. et al. (1967) 51° 10' 122° 07' II n n rr 51° 1 1 ' 122° 02' II II n 11 51° 12' 115° 31 ' Mazama? Halstead, E.C. & Fulton, R.J. (1972) p. 43 51° 13' 122° 16' Bridge River Nasmi th, H. et al. (1967) 51° 15' 121° 59' Bridge River ? Fulton, R.J.T1970 p. 21 51° 23' 116° 08' - Heusser, C.J. (1956) 51° 25' 116° 13' Bridge River Westgate, J.A. S Dreimanis, A. (1967) 51° 27' 121° 13' - Hansen, H.P. (1955) 51° 29' 117° 13.! Bridge River ? Halstead, E.C. & Fulton, R.J. (1972) p. 39 51° 29' 117° 13' St. Helens Y Fulton, R.J. (197 0 p. 21 51° 29 < 120° 13' Bridge River Nasmith, H. et al. (1967) 51° 40' 115° 04' Mazama Beke, G.J. (1969T 51° 43' 115° 41' - Lowden, J.A. & Blake, W. Jr. (1970) p. 69 51° 51 1 121° 39. - Hanse-, H.P. (1955) 51° 53' 119° 18' Bridge River Nasmith, H. ej_a]_. (1967) 51° 56' 116° 45' Mazama Westgate, J.A. & Dreimanis, A. (1967) 51° 58' 116° 30' - Pettapiece, W.W. (1970) 51° 58' 116° 43' - Dyck, W. e_aj_. (1966) p. 108 51° 58' 116° 43' Mazama & Bridge Westgate, J.A. & Dreiimanis, A. (1967) R iver 51° 58' 116° 43' Mazama Lowden, J.A. & Blake, W., Jr. (1968) p. 223 51° 58' 116° 43' Bridge River ? Lowden, J.A. & Blake, W., Jr. (1968) p. 223 51° 58' 116° 43' Bridge River Fulton, R.J. (1970 p. 21 51° 58' 116° 49' St. Helens Y Westgate, J.A. & Dreimanis, A. (1967) 51° 59' 116° 30' - Pettapiece, W.W. (1970) 28
51° 59' 118° 34' Mazama? Mylrea, F.H. (1969) 52° 01' 118° 34' Bridge River Fulton, R.J. (1971) p. 21 52° 01' 123° 35' " " Sneddon, J.I. Pers. observation 52° 02' 116° 48' " " Westgate, J.A. & Dreimanis, A. (1967) 52° 04' 116° 22' - Pettapiece, W.W. (1970) 52° 04' 118° 20' Bridge River Nasmith, H. et al. (1967) 52° 05' 118° 33' " " Mylrea, F.J.Tl9^9) 52° 06' 118° 33' Mazama Fulton, R.J. (1971) p. 21 52° 07-12' 116° 25' - Pettapiece, W.W. (1970) 52° 08' 116° 25' 52° 10' 116° 28' 52° 10' 117° 06' Bridge River Westgate, J.A. S Dreimanis, A. (1967) 52° 12' 116° 27' - Pettapiece, W.W. (1970) 52° 15" 116° 59' - Fulton, R.J. (1968) 52° 33' 113° 34' - Hansen, H.P. (1949b) 52° 33' 117° 36' - Heusser, C.J. (1956) 52° 57' 118° 07' - " " 53° 05' 113° 27' - Hansen, H.P. (1949b) 53° 14' 122° 29' - .. " Hansen, H.P. (1955) 53° 18' 135° 39' Seamount Herzer, R.H. (1971) 53° 27' 114° 21' Mazama Westgate, J.A. et_al. (1969) 53° 27' 129° 28' - Heusser, C.J. (I960T P. 105 53° 30' 113° 33' Mazama Westgate, J.A. et_ al_ (1969) 53° 32' 113° 27' " Lowden, J.A. et_ a_l_. (1970 p. 290 53° 33' 113° 23' " Westgate, J.A. et al. (1969) 53° 34' 114° 52' - Hansen, H.P. (1949c) 53° 34' 116° 31' - " 53° 35' 114° 54'' St. Helens Y Westgate, J.A. et al . (1969) 53° 35' 115° 02' - Hansen, H.P. (\WScT 53° 38' 122° 39' - Hansen, H.P. (1955) 54° 12' 122° 41' - " " 54° 14' 113° 08' - Hansen, H.P. (1969b) 54° 27' 126° 37' - Hansen, H.P. (1955) 54° 37' 122° 38' - " " 54° 44' 112° 29' Mazama Lichti-Federovich, S. (1970) 54° 48' 122° 43' - Hansen, H.P. (1955) 54° 58' 114° 02' - Hansen, H.P. (1952) 55° 02' 113° 33' - " " 55° 03' 118° 12' - " " 55° 05' 122° 45' - Hansen, H.P. (1955) 55° 07' 113° 44' - Hansen, H.P. (1952) 55° 07' 117° 19' - " 55° 10' 117° 46' - " " 55° 13' 119° 14' T . " " 55° 14' 114° 37' 55° 20' 115° 57' - " " 55° 22' 119° 48' - " 55° 23' 116° 43' - " " 55° 26' 131° 40' 55° 27' 131° 48' - Heusser, C.J. (1952) 55° 32' 122° 29' - Hansen, H.P. (1955) 55° 46' 120° 33' 56° 21' 132° 20' - Heusser, C.J. (1952) 56° 28' 132° 22' - " " 29
56° 41 ' 132° 55' - Heusser, C.J • (1952) 11 11 56° 48' 132° 57' - 11 11 57° 03' 135° 20' - 11 11 57° 04' 135° 15' - 57° 05' 122° 37' - Hansen, H.P. (1950a) 57° 09' 135° 35' Mt. Edgecumbe Heusser, C.J . (I960) p. 101 57° 2k' 122° 51' - Hansen, H.P. (1950a) 57° 26' 135° 42' Mt. Edgecumbe Heusser, C.J . (I960) p. 101 11 11 II II 57° 39' 134° 15' 57° 41 ' 130° 47' - Lowden, J.A. et al. (1971) 57° 47' 130° 35' Mt. Edzi za Lowden, J.A. et al. (1967) p 58° 03' 122° 43' - Hansen, H.P. "09 50a) 58° 04' 135° 05' Mt. Edgecumbe Heusser, C.J . (I960) p. 101 11 II II 58° 04' 136° 27' - 11 58° 12' 136° 09' - n II 58° 22' 134° 32' - 11 II II 58° 23' 134° IV - Heusser, C.J • (1952) 11 11 58° 23' 134° 45' - 11 11 58° 24' 134° 39' - 11 11 58° 25' 134° 35' - 58° 25' 134° 37' - • Heusser, C.J . (I960) p. 101 58° 26' 134° 37' - Heusser, C.J . (1952) 58° 27' 134° 40' Mt. Edgecumbe Heusser, C.J . (I960) p. 101 58° 29' 134° 41 ' - Heusser, C.J . (1952) 11 11 58° 29' 134° 47' - 11 11 58° 30' 134° 47' - 58° 36' 122° 39' Hansen, H.P. (1950a) - 11 11 58° 40' 123° 59' - 58° 43' 137° 45' - Heusser, C.J . (I960) p. 101 58° 51' 125° 43' - Hansen, H.P. (1950a) 58° 55' 135° 50' Mt. Edgecumbe McKenzie, G.D . (1970) 59° 36' 126° 37' Hansen, H.P. (1950a) - 11 11 59° 44' 127° 28' - 59° 49' 136° 38' - Hansen, H.P. (1953) 11 11 59° 54' 131° 34' - 11 11 59° 55' 131° 52' - 11 11 59° 56' 131° 16' - 59° 58' 127° 33' - Hansen, H.P. (1950a) 59° 58' 136° 48' Hansen, H.P. (1953) - 11 59° 59' 132° 07' - n II 60° 01' 141° 57' - Heusser, C.J . (I960) p. 101 60° 03' 128° 59' - Hansen, H.P. (1953) 11 60° 03' 131° 00' - " 11 60° 03' 131 ° 00' - " 11 60° 03' 132° 18' - " 60° 04' 129° 12' " 11 - 11 60° 05' 130° 34' - " 11 60° 05' 130° 48' - " 60° 06' 120° 29' - " M 11 60° 06' 129° 27' - " 11 60° 07' 130° 19' - " 60° 09' 120° 36' White River? Wa 1 ms 1 ey, M.Pers . comm. 11 II II 11 11 60° 09' 128° 50' 60° 10' 132° 43' - Hansen, H.P. (1953) 30
60° 12' 129° 54' - Hansen, H.P. (1953) 60° 12' 130° 05' - II II 60° 12' 144° 32' - Heusser, C.J. (I960) p. 101 60° 19' 144° 20' - II II 1 60° 21 134° 04' - Hansen, H.P. (1953) 60° 21 1 144° 34' - Heusser, C.J. (i960) p. 101 60° 22' 146° 35' - Heusser, C.J. (I960) p. 100 60° 27' 133° 37' - Hansen, H.P. (1953) 60° 27' 145° 15' - Heusser, C.J. (i960) p. 100 60° 27' 145° 17' - II n II 60° 28' 129° 41 ' White River Dyck, W. et al. (1966) p. 114 60° 31 ' 134° 19' - Hansen, H.P."Tl953) 60° 34' 145° 40' - Heusser, C.J. (I960) p. 100 60° 37' 141° 05' Whi te R i ver Murray, D.F. (1971) 60° 39' 135° 00' - Hansen, H.P. (1953) 60° 42' 141° 39' White River Murray, D.F. (1971) 60° 46' 138° 35' White River? Stuiver, M. (i960) pp. 556-558 60° 52' 135° 39' - Hansen, H.P. (1953) 61° 03' 138° 22' - Stuiver, M. (1969) pp. 556-558 61° 06' 130° 25' Whi te River? Lowden, J.A. S Blake, W., Jr.(1968 ) pp. 227-230 61° 31 ' 140° 58' 11 II II Lowden, J.A. S Blake, W., Jr.(1968 ) pp. 227-230
61° 37' 137° 2g i White River Lowden, J.A. S Blake, W., Jr.(1970 ) pp. 74-80 61° 37' 140° 49' 11 11 Lowden, J.A. & Blake, W., Jr.(1970 ) pp. 74-80 61° 37' 140° 49' 11 11 Lowden, J.A. S Blake, W., Jr.(1970 ) pp. 74-80 61° 38' 140° 46' : 11 11 Lowden, J.A. & Blake, W., Jr.(1970 ) pp. 74-80 61° 38' 140° 55' 11 11 Lowden, J.A. & Blake, W., Jr.(1970 ) pp. 74-80 62° 00' 119° 35' Whi te R iver? Wa1msley, M. Pers. comm. 62° 01 ' 132° 24' 11 II II n 11 62° 15' 122° 58' 11 II n 11 : :i 1 62° 21 ' 140° 50' White River Rampton, V. (1971) 62° 45' 122° 40' White River? Walmsley, M. Pers. comm. 63° 24' 138° 10' 1nterglacia1 Dyck, W. et aj_. (1966) p. 114 63° 30' 122° 48' White River Walmsley, M. Pers. comm. 63° 30' 137° 16' 1nterglacia1 Lowden, J.A. & Blake, W., Jr.(1968 ) pp. 228-229 64° 28' 140° 27' Whi te R i ver Lowden, J.A. & Blake, W., Jr.(1968 ) pp. 228-229 Most of the ashes that have been observed or detected out• side of the commonly published limits of distribution have been preserved in bog sites. These sites are generally considered to be more favourable for ash preservation. The source of most of these ashes was not identified because of limitations related to the type of study, the amount of material sampled or the available techniques. Once positively identified many of these ashes will extend the limits of detection and usefulness of many of the tephra layers.
THE PRESENCE AND DISTRIBUTION OF ASH IN SOILS
Modem mineral soils are generally considered to be less favourable environments for the preservation of ash than bogs or buried sites due to their relatively more severe weathering environment. Because of the significance of ash in Quaternary studies and the relative paucity of information relative to its distribution in soils in Canada, a number of soils from a relatively wide area in western Canada (see Figure 3) were examined for the presence of ash. With a few exceptions, surface soil samples were collected from relatively stable landscape positions though not from sites that would necessarily be considered favourable for trapping ash at the time of deposition or during subsequent reworking. In the laboratory, organic matter and amorphous coating materials were removed (Kittrick and Hope, 1963) and the samples were sorted by sieving into three size fractions, 500-105^, 105-53yu», 53-20yw. The fraction with a specific gravity of less 32
Bridge River Glacier Peak Mt.St.Helens Y —<._,.—o—<— West Blacktail -—*—-—* Mazama
Figure 3- The location of sites where volcanic ash was found to be present in soils, data presented in Table k, and minimum fallout areas of major ashfalls referred to in Figure 2. TABLE 4
LOCATIONS OF SITES WHERE VOLCANIC ASH WAS LOCATED AND GROSS COMPOSITION
OF THE LIGHT FRACTIONS OF THREE SIZE SEPARATIONS OF THE
NON-ORGANIC MATTER FRACTION
Proportion as % of the light fraction Sample Size % of SG Phytoliths Number Fraction' Latitude N Longitude W <2.490 Ash Phenocrysts Tree Non-Tree Diatoms Type Type
101° X 48° 27' 123° 32' 13.11 4.1 90.1 y 91.87 0.6 94.4 z 6.57 0.7 27.6
105b X 48° 27' 123° 32' 41.44 2.3 0.8 88.5 y 65.57 71.6 5.2 0.7 z 40.61 93.4
106b X 48° 27' 123° 32' 92.83 3.25 94.3 y 67.37 75.0 2.21 1.5 z 1.58 2.3 0.6 2.3
95b X 48° 29' 123° 23* 93.55 8.8 2.0 50.0 y 77.05 11.5 4.8 53.8 z 10.32 1.5 0.7 16.1 a. b. sample from very poorly drained site or o: x. <500y >106y c. sample of ash layer. y. <106y > 53y d. % of specific gravity <2.49. z. < 53V > 20y 34
00 CO un o\ vo O CTl rs r» ro CO rs vO CO VO 00 VO o o r- CO ON Ol OH* oo CN m vO CO oo m oi • • • • • » • vo m o o CM OV rH O •sl- CM vO in CM o O -3" vo CM Oi VO CO 00 rH CO 00 ts Cft N CM r>- Oi O Oi rs rs co sr Oi • • • CM CM vo oo CM CO Oi Oi m CM r» CM Oi o oi m o CO CM 00 rH rs rH VD 00 oo o CM rs rs sd- CM rH oo m <• CM CO sj H H vo oo oi m O CO vo m m Oi oo LO VO IS Ol CM CO m o CM vo vo rs rs vo vo m st rH rH CO rH rs st cji rH VO rH co m oo co rH -si- m rH CM -sl- CO rs CM m 1 m m CM o CM sT o CO o o o CO s* st 00 CM oo CM o in CM CM CM CM CM CM CM oo o oo CM ro -st" m vO VO CM -st O O o O O ro O o o o o o oo o oo Oi ON o Oi ON Oi •sf S* oo -sf -sT Oi •sf Ssf s* X PN N X PN N PN N vO 00 m CO O o\ O rs 76 x 49° 07' 119° 07' 0.35 73.8 9.0 5.7 3.3 y 96.55 18.0 2.1 0.5 5.3 z 3.29 17.6 12.8 X 49° 08' 118° 34' 77.41 91.7 0.9 y 60.02 78.1 7.0 0.9 z 81.69 75.6 1.7 66 X 49° 09' 116° 01' 20.18 66.2 6.2 1.5 0.8 y 44.85 61.4 15.7 0.8 z 76.54 23.0 3.3 6.6 18 X 49° 09' 120° 04' 2.55 72.7 7.2 2.2 y 11.17 49.1 2.6 2.6 z 96.10 9.9 30.6 32 X 49° 10' 120° 05' 13.85 74.6 14.9 y 13.24 63.1 0.8 z 8.72 45.7 13 X 49° 10' 120° 05' 32.50 94.0 3.4 y 53.24 92.1 2.6 0.9 z 91.37 78.5 2.1 .0.37 180 X 49° 10" 124° 43' 0.42 12.4 y 2.89 0.7 64.0 z 0.63 17.0 X 49° 11' 122° 17' 0.52 60.4 4.0 12.9 y 3.32 36.2 29.5 1.9 z 1.74 3.6 3.6 0.9 X 49° 11* 122° 17' 4.77 11.5 0.8 y 6.04 10.3 0.8 z 6. 79 18.8 2.8 81 x 49° 11' 123° 59' 2.97 5.7 y 8.88 3.7 0.7 2.3 4.4 17.9 z 3.50 1.9 1.9 97l X 49° 11' 124° 01' 0.14 9.2 53.2 2.3 0.8 0.39 0.7 2.8 9.9 0.8 0.8 98 X 49° 11' 124° 01' 3.19 5.9 17.8 y 5.81 0.9 82.0 0.9 0.7 z 0.18 2.0 0.7 L 95.8 86 X 49° 14' 124° 03' 84.92 4.2 y 99.71 1.0 3.9 95.0 8.5 89.0 z 99.78 87L X 49° 14' 124° 03' y 62.52 3.2 2.4 4.7 72.4 2.4 74.8 z 99.78 1.6 70 X 49° 15' 117° 58' 40.67 85.2 13.0 y 57.99 79.8 10.1 0.8 0.8 1.5 z 97.10 71.0 2.3 1.5 63 X 49° 15' 117° 58' 27.39 88.2 7.8 y 62.60 77.2 8.7 2.0 2.5 z 99.29 70.8 3.3 167 X 49° 16' 124° 42' 1.96 0.9 y 0.61 3.6 9.2 z 1.72 1.9 174 X 49° 16' 124° 56' 1.21 y 1.36 0.7 9.6 z 3.61 0.6 80 x 49° IV 124° 22' 0.59 6.4 y 14.33 4.9 28.7 z 0.83 1.7 1.7 2.3 12 X 49° 17' 120° 23* 1.20 75.2 7.3 y 13.47 74.5 21.1 z 3.01 22.8 0.7 c 11 X 49° 18' 120 15'. 6.56 76.6 5.4 y 17.26 66.4 8.2 10.4 z 90.88 51.3 1.7 5.2 21.7 75 X 49° 18' 122° 45' 0.87 28.3 5.1 y 16.13 41.6 4.0 37.6 z 0.34 28.4 0.9 11.2 1.7 82b X 49° 19' 124° 25' 7.79 3.6 y 1.42 0.8 16.0 z 0.14 3.6 1.4 4.3 13.0 74 X 49° 20 122° 43' 1.23 16.3 4.1 y 0.68 12.9 1.7 2.6 z 0.56 6.1 0.6 6 X 49° 24 118° 26' 1.87 46.6 7.8 1.9 y 22.50 90.2 8.1 0.8 0.8 z 6.43 29.9 9.4 73 X 49° 28' 123° 41' 0.28 29.1 1.0 y 1.14 2.4 83.9 z 0.08 1.5 36 X 49° 29' 120° 09' 1.67 80.7 12.3 y 11.32 74.8 2.2 z 2.21 44.8 1.0 41 X 49° 30' 123° 40' 0.40 47.2 1.9 y 8.74 40.2 7.7 z 15.86 24.0 42 x 49° 30' 123° 40' 10.10 14.9 y 8.51 7.6 55.1 z 94.78 1.8 74.3 43 x 49° 30' 123° 40' 8.30 44.8 0.9 y 16.14 43.8 0.7 z 2.71 56.5 33 x 49° 32' 120* 23' 7.27 65.1 11.6 y 8.58 50.0 1.6 9.37 45.0 0.8 83 x 49° 40' 124° 59* 1.07 1.4 2.8 3.5 y 7.77 4.4 1.7 4.4 2.2 X 4. 70 3.5 2.8 0.7 85 x 49° 41' 124° 56' 1.15 2.7 8.1 y 6.67 23.9 2.7 z 1.56 0.8 8.6 1.6 34 x 49° 46' 120° 04' 3.87 74. 9.1 y 6.84 57. 3.6 z 29.58 55. 5.5 171 x 49° 51' 124° 05' 0.24 1.5 y 4.52 8.3 z 2.72 9.0 51 x 49° 58* 123° 00' 24.75 84.5 12.4 y 33.66 85.2 9.2 z 2.42 12.2 1.5 52 x 49° 58' 123° 00' 0.13 18.3 60.6 y 11.39 64.7 22.1 z 9.68 40.2 42.3 CO 142 x 50° 00' 123° 05' 0.42 17.3 1.7 4.3 y 1.94 31.6 0.9 17.5 z 0.19 7.2 51.8 149 X 50° 02' 122° 51' 0.94 76.3 5. y 7.17 44.9 17. 1.0 z 2.41 24.2 1. 150 X 50° 02' 122° 51' 1.99 47.3 11.0 y 5.38 28.1 25.0 z 1.42 6.3 88 X 50° 04* 125° 19' 0.15 3.4 1.7 y 1.10 11. 1.3 2.5 z 0.26 3. 4.5 107 X 50° 13' 126° 40' 0.44 3. 2.6 5.2 y 1.08 1. 10.1 0.7 z 7.89 2. 89 X 50° 15' 125° 44' 1.42 1.5 8.7 y 5.95 4.0 10.5 z 0.72 177 x 50° 16' 125° 42' 0.47 y 2.53 1.2 27.8 z 0.81 0.5 3.6 79 X 50° 18' 125° 54' 4.91 y 1.49 0. 1.8 z 0.18 1. 90 x 50° 21' 125° 54' 7.22 6.2 30.4 y 71.03 7.3 62.8 z 12.51 0.9 20.7 20.7 173 x 50° 27' 126° 12' 6.56 3.6 y 5.46 1.8 37.6 z 12.18 0.5 1.0 69 x 50° 34' 119° 00' 0.70 y 1.24 2.0 z 0.90 176 x 50° 34' 127° 07' 0.65 y 4.24 1.0 0.5 z 5.11 1.8 0.9 1 178 x 50° 3b 126° 27' 1.87 y 2.69 1.2 1.2 z 2.45 0.8 182 x 50° 36 127° 25' 0.53 y 0.98 0.7 0.71 z 0.85 1 140 x 50° 42' 121° 21 3.22 69. 2.0 y 3.04 34. 5.0 z 7.07 12. 0.9 111 x 50° 50' 122° 55' 37.83 60.9 36.4 y 32.24 80.8 14.4 67.4 z 11*23 12.4 1.1 58 x 51° 00' 122° 11' 20.35 91.5 7.0 y 28.14 76.3 10.7 z 1.28 10.5 0.8 4.8 60 x 51° 00* 122° 11' 0.82 3.7 y 3.21 4.6 o z 0.43 3.6 1.4 20 x 51° 02' 121° 46' 17.08 82.5 13.4 1.0 y 13.36 61.9 8.6 3.8 z 1.20 30.9 17.5 120 X 51° 06' 121° 52' 40.12 78.0 22.0 y 33.79 90.3 8.7 z 1.43 60.9 4.5 2.3 18.1 151 X 51° 07' 123° 36' 1.49 74.0 5.2 y 4.86 45.6 6.0 z 8.16 41.7 6.7 65l X 51° 13' 120° 07' 93.78 89.6 10.4 y 92.93 96.0 2.4 z 97.94 88.2 7.4 54 X 51° 15' 118° 30* 13.24 96.9 0.8 y 69.53 78.8 10.6 z 0.34 84.9 5.9 55 X 51° 15' 118° 30' 90.54 88.6 5.7 3.3 0.8 y 30.10 68.3 5.0 9.2 z 1.02 53.5 2.3 0.8 0.8 56 X 51° 15' 118° 30' 77.00 32.4 7.9 y 73.27 86.8 4.4 1.5 z 89.99 73.2 2.0 4.7 116 X 51° 17' 121° 43' 30.39 75.7 20.6 y 30.21 79.3 19.0 z 13.23 51.4 7.2 7.2 21 X 51° 20' 121° 04' 20.13 81.0 7.0 2.1 y 14.76 55.6 4.6 10.2 5.5 z 0.96 38.4 26.8 127 x 51° 22' 121° 10' 13.24 85.5 11.3 3.2 y 12.56 86.9 4.1 5.7 z 43.5 27.2 3.5 6.1 30 x 51° 38' 121° 14' 34.66 93.8 6.2 y 90.43 71.1 10.7 z 49.90 49.0 6.1 40 x 51° 42" 122° 55' 1.09 74.4 16.3 y 2.25 50.0 2.8 z 0.19 11.2 0.8 39 x 51° 57' 122° 17' 8.44 15.2 0.7 y 10.47 35.1 2.3 z 10.36 5.4 19 x 51° 59' 121° 25' 2.85 78.0 21.3 y 16.29 64.9 6.9 z 5.60 42.9 1.0 16.2 160 x 52° 01' 123° 10' 1.87 19.5 11.5 y 4.75 14.9 10.9 z 10.80 1.6 162 x 52° 07' 123° 55' 0.37 18.2 3.0 y 2.79 16.6 z 2.22 1.8 16 x 52° 21' 122° 07' 0.42 44.7 6.1 8.8 3.5 y 0.95 19.1 1.9 7.6 2.9 z 0.78 8.4 1.2 13.8 163 x 52° 21' 123° 34' 1.29 58.5 3.3 y 3.50 48.8 3.2 z 2.16 10.4 88.0 15 x 52° 23' 122° 23' 0.99 67.2 13.4 44.3 0.8 1.5 y 8.65 1.32 7.5 1.5 2.3 z 14 X 52° 27' 122° 05' 5.65 48.8 3.2 4.8 y 21.26 66.3 2.5 2.5 15.3 z 8.11 11.8 23.0 6 35 X 52° 47' 122 22' 3.34 57.0 13.0 y 11.04 41.0 5.8 z 1.98 25.0 1.0 147 X 52° 53 121° 26' 0.54 12.5 0.8 y 0.95 31.6 3.4 z 0.76 0.8 0.8 148 X 52° 53' 121° 26' 0.09 25.7 2.8 y 2.80 30.3 0.7 z 4.57 3.3 31 x 53° 10' 122° 20' 3.37 24.3 3.7 y 3.62 42.0 6.3 3.37 22.7 3.8 z 161 x 53° 23' 123° 01' 1.61 7.3 2.28 36.1 3.7 4.6 1.9 y 7.10 0.6 1.1 0.6 z 143 54° 07' 121° 38 0.11 11.8 0.71 15.8 x 0.00 y 71 Xz 54° 15' 126° 50' 0.26 26.4 4.1 0.8 y 0.49 4.4 2.8 z 0.20 0.9 166 x 54° 17' 128° 36' 0.59 0.8 y 3.40 z 9.98 72 x 55° 10' 128° 00' 0.58 3.6 y 0.37 3.2 z 0.57 1 165 x 55° 32 126° 33' 0.93 2.7 y 1.51 z 9.91 153 x 56° 15' 120° 10' 1.66 9.0 y 5.13 17.3 0.8 3.2 0.82 0.9 3.4 z 154 x 56° 30' 122° 20' 2.78 1.7 y 1.44 4.4 0.8 z 7.34 0.8 157 x 58° 40' 122° 41' 5.75 y 6.53 3.2 3.59 z 1.5 156L x 58° 54' 123° 09' 43.38 y 28.20 11.2 0.9 2.48 1.2 0.6 z 2.5 24 x 60° 05' 128° 30' 5.08 89.3 y 7.84 64.5 0.25 43.6 z 23 x 60° 05' 128° 45' 11.71 100.00 y 12.76 79.3 4» z 0.47 31.5 22 x 60° 20' 129° 00' 5.43 94.5 y 9.35 77.6 z 0.45 48.0 25l x 60° 25' 120° 45' 84.97 100.0 y 89.31 100.0 z 99.10 100.0 46 x 61° 37' 115° 39' 3.41 y 6.47 10.3 0.9 z 0.83 1.4 0.7 v 62 x 61° 50' 140° 06' 44.40 100.0 y 8.70 65.4 4.6 z 97.15 91.7 3.2 2T x 62° 25' 123° 00' 70.15 96.2 y 76.96 94.7 z 98.34 95.6 26v x 62° 50' 122° 45' 85.89 97.7 y 76.86 97.9 z 98.33 98.3 48 x 63° 04' 126° 36' 79.29 93.2 5.8 y 73.87 89.7 3.7 99.82 z 79.4 10.9 47 x 63° 17' 129° 45' 78.97 86.8 7.9 y 76.00 99.3 0.7 z 99.03 96.0 2.0 49 x 63° 37' 127° 56' 4.67 28.7 2.6 y 14.98 54.2 5.3 z 12.34 23.2 46 than 2.49 was separated from each size class by heavy liquid separation. Over 200 grains were examined in each light frac• tion using a petrographic microscope. The percentage of glass shards, glass encased phenocrysts, diatoms and phytoliths was determined. The remaining percentage of grains was made up of non-opaque light minerals. The results (see Table 4 and Figure 3) indicate that the preservation of ash in soils is as widespread as that in the generally more favourable locations for preservation recorded in the literature. The results of determinations on soils within the fallout paths shown in Figure 3 indicate that soils retain ash to varying degrees. The presence of ash depends on conditions prevailing at the time of deposition and subsequent geomorphic processes. Redistribution of ash into more favour• able landscape positions, such as depressions, bogs and areas of active sedimentation, makes these relative accumulations the ones most easily recognizable in Quaternary studies and in determining the limits of ash distribution. Many of the sites in Figure 3 contained minor amounts of ash and identification of the source may be difficult. However, this difficulty may be overcome using some of the latest techniques available, such as electron microprobe analysis, requiring only a limited number of shards or phenocrysts. Identification of the source of the ash in the soils was not attempted as the object of the investigation was to determine the relative amounts and extent of ash beyond the limits of distribution of ash currently published in the literature. 47 The presence of phytoliths and diatoms was noted in the grain counts of some of the light mineral fractions. Phytoliths consist of biogenic hydrated silica whose specific gravity ranges from 1.5 to 2.3 and whose refractive index ranges from 1.410 to 1.465 (Jones and Beavers, 1963). Phytoliths have been classified (Twiss et al., 1969; Rovner, 1971) on the basis of their morphology, which is characteristic of the vegetative species of origin. Not all species necessarily form phytoliths and even in those that do environmental variables can influence their formation (Raeside, 1970). They occur in a variety of soils and sediments and can be used as environmental indicators. Their occluded carbon content can be dated. Rovner (1971) reviewed some of these aspects in his discussion on the poten• tial use of phytoliths in paleoecological studies. The only distinction made in the tabulated data is between those phytoliths characteristic of tree species and those of non-tree species. The former were dominated by those character• istic of coniferous trees (Rovner, 1971; Brydon et al., 1963) while no distinction was made as to the dominant characteristics of the latter type. Where diatoms were encountered the non-tree type of phytoliths tended to dominate. The greatest percentage of phytoliths was found in soils from the biologically more productive regions of the sampling area, in the south and west. Jones and Beavers (1964) similarly found the greatest percentage of phytoliths in the most productive soils of the soil catenas they studied. 48 Diatoms are aquatic single celled plants that secrete siliceous frustules. The frustules of dead cells have some properties that are similar to phytoliths though their morphology is quite distinct. They may be considered as analagous to phytoliths as indicators of certain conditions in an acqueous environment. Several organic or very poorly drained soils were sampled and some of these were found to contain diatoms. CONCLUSIONS The widespread presence of volcanic ash in many soils in western Canada indicates that once separated and identified, a useful source of information may exist for certain Quaternary studies and that the detectable limits of some ash layers may be extended. The tabulations of the references and locations where ash has been observed and in some cases identified, may serve to indicate the probability of ash being present in an area. An awareness of the local conditions that might have affected ash deposition and its subsequent redistribution and of the techniques available for its characterization and identi• fication are important in any study considering the use of ash as a factor in making interpretations. 49 REFERENCES ARMSTRONG, J.E. and FULTON, R.J. (1965). In "Guidebook for Field Conference J., Pacific Northwest, INQUA, VII Congress, U.S.A. 1965." Nebraska Academy of Sciences, Lincoln, Nebraska. AUMENTO, F. and SOUTHER, J.G. (1973). Fission track dating of Late Tertiary and Quaternary volcanic glass from Mount Edziza volcano, British Columbia. Canadian Journal of Earth Sciences 10, 1156-1163. BEKE, G.J. (1969). "Soils of three experimental watersheds in Alberta and their hydrologic significance." Ph.D. thesis. University of Alberta, Edmonton, Alberta. BEKE, G.J. and PAWLUK, S. (1971). The pedogenic significance of ash layers in the soils of an east slopes (Alberta) watershed basin. Canadian Journal of Earth Sciences 8, 664-675. BERGER, A.R. (1960). On a recent ash deposit, Yukon Territory. Proceedings Geological Association of Canada 12, 117-118. BLACK, R.F. (1958). wrangell Mountains. Iri "Landscapes of Alaska." (H. Williams, Ed.), pp. 30-33. University of California, Press, Berkeley. BLAKE, W. Jr. (1970). Studies of glacial history in Arctic Canada, 1. Pumice, radiocarbon dates and differential postglacial uplift in eastern Queen Elizabeth Islands. Canadian Journal of Earth Sciences 7, 634-664. BOCKHEIM, J.G., SCHLICTE, A.K., CRECELIUS, E.A., KUMMER, J.T., PONGSAPICH, W., TENBRINK, N.W., WEBER, W.M. and GRESENS, R.L. (1969). Compositional variations of the Mazama ash as related to variation in weathering environment. Northwest Science 43, 162-173. BOSTOCK, H.S. (1952). 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Volcanic ash chronology. In_ "The Quaternary of the United States." (H.E. Wright Jr. and D.G. Prey, Eds.), pp. 807-816. Princeton University Press, New Jersey. WILCOX, R.E. (1969). Airfall deposits of two closely spaced eruptions in late glacial time from Glacier Peak volcano, Washington. Geological Society of America, Abstracts 88-89. WILLIAMS, H. (1969). The ancient volcanoes of Oregon. Condon Lecture, Oregon State System of Higher Education, Eugene, Oregon. WRIGHT, F.E. (1905). The Unuk River mining region of British Columbia. Geological Survey of Canada, Summary Report, pp. 46-53. bl A STUDY OF TWO SOILS DERIVED FROM VOLCANIC ASH IN SOUTHWEST BRITISH COLUMBIA INTRODUCTION A large area of western Canada has been subjected to surface additions of volcanic ash (Sneddon, 1973a). Soils studies have found that the weathering products of volcanic ash possess a number of unique physical chemical and mineralogical character• istics (Japanese Government, 1964; FAO, 1964; IAIAS, 1969). The influence of the ash layer on soils depends on the character• istics of the ash. Soils derived entirely from volcanic ash occur in deep ash deposits. With decreasing thicknesses of ash, pedogenic processes operate in the ash layer and in the underlying material. Eventually ash layers become too thin to be recognized by the naked eye yet still may have some influence on soil characteristics. Ash layers are incorporated into soils through disturbance or occur as a layer in soils due to burial after deposition. In Canada soils derived from volcanic ash occur in the vicinity of the White and Klutlan Rivers in the southwest Yukon and in the vicinity of Mount Edziza and the upper reaches of the Bridge and Lillooet Rivers in British Columbia. These areas are in close proximity to volcanoes which have been sources of Recent tephra. Throughout the rest of western Canada where ash has fallen the soils are partially developed from or have been influenced by the presence of ash. 62 Figure 1. Location of the study sites and adjacent climate stations. 63 The influence of the presence of volcanic ash on soils in Canada has received limited attention so far and soils derived from volcanic ash have not been studied. This paper describes two soils derived from volcanic ash and underlain by paleosols, and presents selected analyses to characterize these soils. THE MORPHOLOGY AND ENVIRONMENT OF TWO VOLCANIC ASH SOILS The two soils are located in southwestern British Columbia (see Fig. 1). Site 1 is located in the Camelsfoot Range of the Southern Plateau and Mountain physiographic region and site 2 lies at the eastern edge of the Coast Mountain physiographic region (Holland, 1964). The soils were described using standard terminology and procedures. (Soil Survey Staff, 1951; Canada Soil Survey Committee, 1970). Site 1. Location: Latitude 50°00'N, Longitude 122°!!^, in the Camelsfoot Range, 6 km west of Hogback Mountain. Classification: Alpine Dystric Brunisol over a paleo Alpine Dystric Brunisol - Mini Humo-Ferric Podzol integrade. (Andic Sombric Brunisol over a paleo Orthic Humo-Ferric Podzol)3. Vegetation: willow Salix cascadensis mountain sandwort Arenaria capillaris Classification revision as proposed at the Canada Soil Survey Committee Meetings, Saskatoon, 1973. 64 varileaf cinquefoil Potentilla diversifolia wormskjold speedwell Veronica wormskjoldii alpine timothy Phleum alpinum cusick bluegrass Poa cusickii timberline bluegrass Poa rupicola dunhead sedge Carex phaeocephala woodrush Luzula arcuata Biogeoclimatic Zone (Krajina, 1965) : Alpine Zone of the Alpine Tundra Region Parent material: - 24 cm fine over ± 12 cm coarse volcanic ash over colluvium of weathered conglomerate and sandstone over weathered sandstone. Topography: Strongly sloping and moderately rolling 10-12 percent NW facing slope. Elevation: 2,124 m. Dra inage : Well drained, moderately rapid to rapid perme• ability and slow surface water runoff. Soil moisture Moist. Remarks: Solifluction processes are active in the vicinity as evidenced by the presence of solifluction lobes. Horizon Depth cm Ah 0-7.5 Very dark brown (10 YR 2/2 m), (10 YR 3.5/2 d) sandy loam; weak to coarse medium granular; very friable; abundant fine roots; very strongly acid; abrupt wavy boundary; 7.5 - 12.5 cm thick. 65 Horizon Depth cm Bm 1 7.5-12.5 Yellowish brown (10 YR 5/4 m), (10 YR 5/3 d) sandy loam; weak coarse to medium granular; very friable; abundant fine roots; strongly acid; abrupt wavy boundary; 2.5 - 7.5 cm thick. Bm 2 12.5-23 Very pale brown (10 YR 7/3 m), (10 YR 7/2 d) sandy loam; weak fine granular; very friable; plentiful fine roots; strongly acid; abrupt wavy boundary; 10 - 15 cm thick. Bm 3 23-24 Very pale brown (10 YR 7/3 m), (10 YR 7/2 d) sandy loam; strong fine platy; very friable; plentiful fine horizontally orientated roots; strongly acid; abrupt wavy boundary; 0.5 - 1 cm thick. Bm 4 24-29 Brownish yellow (10 YR 6.5/6 m), (10 YR 6/4 d) loamy sand; single grain; loose; plentiful fine roots; strongly acid; abrupt wavy boundary; 3 - 5 cm thick. CB 29-36 Yellow (10 YR 8/6 m), (10 YR 7/2 d) sandy loam; single grain; loose; few fine roots; strongly acid; abrupt wavy boundary; 5 - 10 cm th ick. II Bhfb 36-41 Black to dark reddish brown (5 YR 2/1.5m), (10 YR 3.5/2.5d) loam; moderate medium to fine angular blocky; friable; very few fine roots; 20 percent angular and rounded cobbles and gravel; strongly acid; abrupt wavy bound• ary; 5 - 7.5 cm thick. 66 Horizon Depth cm II Bfb 41-46 Dark brown to brown (5 YR 2/1.5 m), (10 YR 4.5/3 d) loam; moderate medium to fine angular blocky; friable; common very fine vesicular pores; 20 percent angular and rounded cobbles and gravel; medium acid; abrupt wavy boundary; 5 - 7.5 cm thick. II BCb 46-54 Yellowish brown (10 YR 5/5 m), (10 YR 4.5/5 d) sandy loam, moderate coarse breaking to very fine subangular blocky; friable; common very fine vesicular pores; 20 percent angular and rounded cobbles and gravel; slightly acid; clear wavy boundary; 7 - 10 cm thick. II CBb 54-105+ Brownish yellow (10 YR 6/8 m), (10 YR 5.5/6 d) sandy loam; moderate coarse breaking to very fine subangular blocky: friable; neutral; weathered sandstone. Site 2. Location: Latitude 50°51' N, Longitude 122°55'W, 8.8 km from Goldbridge and about 0.5 km southwest of Gun Lake. Classification: Orthic Regosol over a paleo Orthic Eutric Brunisol. (Orthic Regosol over a paleo Orthic Eutric Brunisol)3 'Classification revision as proposed at the Canada Soil Survey Committee Meetings, Saskatoon, 1973. 67 Vegetation: lodgepole pine Pinus contorta latifolia Douglas fir Pseudotsuga menziesii alder Alnus sp. willow Salix sp. kinnikinnick Arctostaphylos Uva-ursi twin flower Linnaea borealis fireweed Epilobium anqustifolium grouseberry Vaccinium scoparium rose Rosa sp. mosses (Krajina, 1965) : Interior Douglas-fir Zone of the Canadian Cordilleran Forest Region. Pseudotsuga-Arctostaphylos-Calamagrostis Association of the Pseudotsuga menziesii Zone of Brayshaw (1965). Parent material: i 10 cm fine over i 38 cm coarse volcanic ash over undifferentiated glacial drift. Local bedrock and occasional gravel in pedon is dioritic. Topography: Strongly sloping. 10 percent N facing slope. Elevation: 898 m. Dra inage: Moderately well drained, rapid permeability and very slow to slow surface water runoff. Soil moisture: Mo ist. Horizon Depth cm 6.5-5 Loose litter of leaves, needles and twigs. 68 Horizon Depth cm LFH 5-0 Very dark brown (10 YR 2/2 m), (10 YR 3/3 d) twigs, needles and semi-decomposed leaves; mosses and humus material; strongly acid; abrupt smooth boundary. Ah 0-11 Light gray (10 YR 7/1 m), (10 YR 7.5/1 d) sandy loam; weak fine granular; very friable; plentiful fine and very fine roots; slightly acid; abrupt wavy boundary; 9 - 11 cm thick. Cl 11-25 Light gray (10 YR 7/1 m), (10 YR 8/1 d) fine gravelly sand; single grain; loose; abundant medium to very fine roots; neutral; abrupt smooth boundary; 10 - 15 cm thick. C2 25-48 Light gray (10 YR 7/1 m), (10 YR 8/1 d) and very pale brown (10 YR 7/3.5 m), (10 YR 8/6 d) pseudo many fine to medium mottled fine gravelly sand; single grain; loose; abundant medium to very fine roots; neutral; abrupt smooth boundary; 20 - 25 cm thick. II Bmb 48-61 Brown (10 YR 4.5/3m) sandy loam; moderate medium to coarse subangular blocky; friable; few fine and medium roots; neutral; abrupt wavy boundary; 10 - 15 cm thick. 69 Horizon Depth cm II BCb 61-86 Dark gray, olive gray to gray (5 Y 4.5/1.5 m 2.5 Y 5/2 d) common fine to medium distinct mottles, sandy loam; moderate medium to coarse subangular blocky; neutral, clear smooth boundary; very few fine and medium roots; neutral; 22 - 27 cm thick. II CBb 86-100+ Dark gray, olive gray to gray (5 Y 4.5/1.5 m (5 Y 5/2 d) common fine to medium distinct mottles, sandy loam; moderate medium to coarse subangular blocky; friable; very few fine and medium roots; neutral. At site 1 the vegetation is characteristically alpine and does not seem to have been significantly influenced by the edaphic conditions associated with volcanic ash. At site 2 the dominance of lodgepole pine suggests that edaphic conditions associated with ash may have influenced the vegetative species present. If this is the case an amelioration is taking place as indicated by the other species present. The fire history in the area could also account for the dominance of lodgepole pine. Studies of other ashfalls in the Pacific Northwest (Hansen, 1947; Heusser, 1952) indicate that lodgepole pine usually dominates the post ashfall vegetative succession until suffici• ent amelioration has taken place. Table 1. Climatic records of stations adjacent to the study sites (Abstracted from Atmospheric Environment Service, 1972). Type of Element and Station Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Year Normal Bralorne Latitude 50°47'N Longitude 122°49'W Elevation 3330 Ft. ASL Mean Daily Temp. (Deg. F) 18 .2 26 .2 31 •5 40 .0 47 .9 53.1 58.9 57.5 51.5 40., 8 28 .9 21 .7 39.7 3 Mean Daily Maximum Temp. 2k, .8 3k .3 41. 5 50 .8 61 .3 65.7 73., 8 71 .3 64.7 49.. 5 35 . 1 27.. 8 50.1 3 Mean Daily Minimum Temp. 1 1.6 . 18 .0 21 .5 29 .2 34 .5 40.5 43.9 43.7 38.3 32. ,0 22 .7 15.. 9 29-3 3 Extreme Maximum Temp. 52 58 68 87 96 93 100 97 96 87 60 52 100 2 No. of years of Record 26 26 24 25 27 27 27 25 24 28 27 24 Extreme Minimum Temp. -33 •25 •19 1 16 28 29 30 22 -2 •20 •21 -33 2 No. of years of Record 26 26 24 25 27 27 27 25 25 28 28 26 No. of Days with Frost 29 27 29 22 12 1 5 17 27 29 198 4 Mean Rainfall (inches) 1 .79 0.74 0. 70 0.6 8 0• 99 1.69 1..3 4 1.31 1.64 3..2 5 1 .94 2,.3 2 18.39 8 Mean Snowfa11 25 .1 16 .1 12. 0 4. 1 0• 9 T 0., 0 0.0 T 4,. 3 19 • 3 22,. 6 104.4 3 Mean Total Precipitation 4 .30 2 .35 1 .90 1 .09 1 .08 1 .69 1 .3,4 1.31 1.64 3..6 8 3.8 7 4.58 28.83 8 Greatest Rainfall in 24 Hrs. 2,.4 6 1 .42 2.0 0 2.7 6 1 .26 1 .56 2.65 1.55 2.75 2..0 0 2.0 2 2, • 51 2.76 1 No. of years of Record 35 36 35 37 38 37 37 37 32 34 37 33 Greatest Snowfall in 2k Hrs. 2k .5 19 .5 12. 0 8. 5 4. 1 0.5 0,. 0 0.0 2.1 8.0 14 .0 18.0 24.5 1 No. of years of Record 35 37 35 37 38 39 38 38 37 38 37 33 Greatest Pptn in 2k Hrs. 2.7 0 1 .95 2.0 0 2.7 6 1.2 6 1.56 2,.6 5 1.55 2.75 2,,1 6 2.02 2.5 8 2.76 1 No. of years of Record 3k 35 35 37 38 37 37 37 32 34 37 33 No. of days with Measurable Rain 2 2 1 4 5 8 5 7 7 8 5 3 57 3 No. of days wi th Measurable Snow 8 5 5 3 1 0 0 0 2 7 8 39 3 No. of days wi th M. Precipitation 9 6 6 6 6 8 5 7 7 10 11 10 91 3 o Table 1 (continued) Type of Element and Station Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Year Norma 1 Bridge River*3 Latitude 50°44'N Longitude 122°13'W Elevation 830 Ft. ASL Mean Rainfall (inches) 1.34 1 .07 0.92 0.91 0.59 0.90 0.73 1.25 1.12 2.22 1.13 1 8.1 13.99 8 Mean Snowfa11 20.0 10.6 4.0 0.6 0.0 0.0 0.0 0.0 0.0 0.3 8.0 16.0 59.5 8 Mean Total Precipitation 3-34 2.13 1 .32 0.97 0.59 0.90 0.73 1.25 1 .12 2.25 1.93 3. 41 19.94 8 Greatest Rainfall in 24 Hrs. 1.40 1 .50 1.40 1.04 1.15 1 .40 2.93 1.02 1.11 2.33 1 .63 2. 22 2.93 4 No. of years of Record 17 17 16 16 16 16 16 17 17 17 17 17 Greatest Snowfall in 2h Hrs. 22.0 22.0 2.0 T 0.0 0.0 0.0 0.0 0.0 1 .3 12.0 20. 5 22.0 4 No. of years of Record 17 16 16 16 16 16 17 17 17 17 17 17 Greatest Precip. in 2k Hrs. 2.20 2.20 1.40 1 .04 1.15 1.40 2.93 1.02 1.11 2.33 2.28 2. 62 2.93 4 No. of years of Record 17 16 16 16 16 16 16 17 17 17 17 17 No. of Days with Meas. Rain 8 6 6 8 7 8 5 8 7 11 11 9 94 5 No. of Days with Meas. Snow 6 4 1 0 o. 0 0 0 0 * 2 5 18 5 No. of Days with M. Precip. 13 9 6 8 7 8 5 8 7 11 12 14 108 5 L i1looet Latitude 50°42'N Longitude 121°56'W Elevation 950 Ft: . ASL Mean Rainfall (inches) 1 .01 0.86 0.66 0.76 0.83 1.12 1.00 1.02 1.29 1.81 1 .19 1.3 1 12.86 8 Mean Snowfa11 9.7 3.8 1.2 0.5 0.0 • 0.0 0.0 0.0 0.0 T 3.0 7. 2 25.4 3 Mean Total Precipitation 1 .98 1 .24 0.78 0.81 0.83 1 .12 1.00 1.02 1 .29 1.81 1 .49 2. 03 15.40 8 Greatest Rainfall in 2k Hrs. 1.95 1 .40 0.75 1 .36 1.94 4.50 2.02 1.07 1 .08 1.90 1.43 1 3.0 4.50 1 No. of years of Record 51 55 49 52 48 50 50 51 49 49 53 49 Greatest Snowfall in 2k Hrs. 20.5 10.0 4.7 3.9 0.0 0.0 0.0 0.0 0.0 1.5 6.0 13.0 20.5 1 No. of years of Record 50 54 50 53 51 53 52 53 52 50 51 50 Greatest Precip. in 2k Hrs. 2.05 1.40 0.75 1.36 1.94 4.50 2.02 1.07 1 .08 1.90 1.43 1. 30 4.50 1 No. of years of Record 50 54 49 52 48 50 50 51 49 49 52 48 No. of Days with Meas. Rain 3 4 4 4 5 5 4 6 7 7 6 5 60 3 No. of Days with Meas. Snow 5 2 1 0 o- 0 0 0 2 4 14 3 No. of Days with M. Precip. 8 5 5 5 5 5 4 6 7 8 9 73 3 aActual period of record as per code number: 1. 30 yrs. between 1941 and 1970 4. 15-19 yrs. between 1941 and 1970 ^ 2. 25-29 yrs. between 1941 and 1970 5- 10-14 yrs. between 1941 and 1970 «- 3. 20-24 yrs. between 1941 and 1970 8. Adjusted Lat. and Long, corrected from that published. 72 Krajina's (1965) biogeoclimatic classification provides a useful guide in assessing the climate at each site which may be further supplemented by the data available from climatic stations closest to the study areas (Bralorne, Bridge River, and Lillooet; see Table 1 and Fig. 1). At site 1 the total precipitation is probably more than that at Bralorne and less than the average figure given by Krajina (1965). Alpine areas to the west receive more precipitation while this area receives less. Snow• banks accumulate in the vicinity of site 1 which lies on the leeward side of the mountain ridge. These accumulations result in a relative increase in the total precipitation received in this area. Soils insulated by snow pack are less likely to freeze in the winter. Soil water is maintained into early summer by the duration of the snowpack. Also during the rest of the summer, frequent clouds at this elevation and precipita• tion maintain the soils in a moist state. The climate at site 2 is probably most similar to that at Bralorne (see Table 1). The vegetation at the site when compared to that at Bralorne indicates the site is a little drier. A period of relative drought occurs during the summer months and the soils may approach a comparatively dry condition during this period. The two soils described have been derived from the approx• imately 2,440 year old Bridge River volcanic ash. The ash has been described as dacitic (Stevenson, 1947) . Nasmith e_t al. (1967) have described the distribution and some of the properties of the ash. Sneddon (1973d) presents some total chemical analyses. At both sites a particle size discontinuity occurs. 73 The upper ash layer consists of fine ash while the lower layer consists of coarse ash. At site 2, closer to the eruption source, the lower layer consists of coarse ash and lapilli. This reflects an initially more violent eruption having taken place followed by a less violent eruption of finer materials. The sharp contact between the two layers indicates that the eruption took place in two stages rather than in a single eruption with differential settling. In the latter case a graduation in particle size would be expected. Nothing was observed or has been recorded that indicates a significant time interval separated the deposition of these layers. Birrell (1964) noted that there was often a layer of coarse particles, ejected in the early stage of ash eruptions, that formed the parent materials of volcanic ash soils in New Zealand. The weathering of dacitic volcanic ash results in soils less rich in allophane than in the weathering of less siliceous ashes (Wright, 1964). Andesitic ashes yield more allophane and are associated with the more classical type of volcanic ash soils which have been the subject of most studies. Due to its physical characteristics, internal porosity and shard shape, volcanic ash has a larger weathering surface than most other parent materials of the same particle size range. In addition ash layers tend to be of uniform size are non-indurated and permeable. These factors indicate the weathering potential of ash from a physical standpoint. 74 According to the chemical analysis (Stevenson, 1947; Sneddon, 1973d) the Bridge River ash has a weathering potential index of about 20. similar values have been obtained for labradorite and basalt (Carroll, 1970, p. 35). Fieldes and Swindale (1954) write that acidic ashes have a weathering potential similar to feldspars. Egawa (1964) indicates that volcanic glasses are very unstable on the basis of their relative decrease in soils with increase in weathering. The weathering potential of ash is most probably related to the weathering potential index and has a weathering potential similar to feldspar when comparisons are made on the basis of effective surface area. MATERIALS AND METHODS The two soils were sampled by horizon based on maximum expression of soil genesis as reflected in the morphological characteristics at each site. In the laboratory the samples were processed to pass a 2 mm sieve then stored in a moist state, drying being minimum. A few drops of toluene were added to inhibit microbial activity. The following determinations were conducted: particle size analysis by the pipette method (Day, 1965) on an organic matter and iron oxide free (Mehra and Jackson, 1960) fine earth fraction using Na2C03 as a dispersing agent; fine clay content from an aliquot taken from the soil suspension after centrifugation (Jackson, 1956); bulk density using paraffin coated clods and core sampler for loose material (Soil Survey 75 Staff, 1967, 4A2, 4A3); 15 bar water retention on a pressure plate apparatus (Soil Survey Staff, 1967, 4Bla); pH using a glass electrode pH meter on 1:1 soil to water, 1:2 soil to 0.01 M CaCl2 and 1:50 soil to IM NaF; total carbon by combus• tion in an induction furnace using a 'Leco' gasometrie carbon analyser (Leco, 1959); cation exchange capacity by 1.0 N neutral NH40Ac procedure (Soil Survey Staff, 1967, 5A1) ; exchangeable bases by atomic absorption (Soil Survey Staff, 1967, 5B1); acid ammonium oxalate extractable Fe and Al (McKeague and Day, 1966); extractable phosphorus by the Bray 1 method (Olsen and Dean, 1965); and pH-dependent cation exchange capacity (Clark e_t al., 1965). Correlation coefficients were determined at the U.B.C. computing centre using the U.B.C. TRIP subroutine program. RESULTS AND DISCUSSION The study revealed that neither of the soils having ash parent material exhibited a high degree of development. Harwood and Youngberg (1969) similarly found that soils derived from the approximately 6,600 year old Mazama pumice in the Pacific Northwest were still relatively fresh and unweathered. Horizon differentiation is more marked at site 1 which is subject to the greatest amount of leaching and is associated with soils exhibiting podzol and dystric brunisol characteristics. Soil horizon colors range from very dark brown at the surface to very pale brown and yellow. The particle size discontinuity from fine to coarse ash at 24 cm has affected water movement 76 down through the pedon. As a result a strong fine platy struc• ture and horizontal root orientation is evident just above the discontinuity where soil water movement is impeded. The Bm 4 horizon has developed in the coarser material below this dis• continuity and has been maintained in a relatively more humid and aerated condition which is favourable for soil weathering to take place. Thus the Bm 4 horizon initially appears to be a buried horizon. Horizon differentiation is weakly expressed in the soil developed at site 2. This site is associated with eutric brunisolic soils and a drier climate with a relatively dry period during the summer months. A light gray color is characteristic of the ash horizons. In addition, the C2 horizon has a mottled appearance which does not reflect poor drainage but rather the retention of soil water in internal capillary channels of the coarser vesicular particles. In their relatively well aerated environment these local areas of higher moisture content provide a more favourable environment for soil weathering. The particle size discontinuity at 11 cm is not reflected in the morphology of the soil developed at site 2 as at site 1. This is considered to be due to the relatively thinner fine ash layer which has a lower water-holding capacity than the 24 cm layer at site 1, and more readily transmits water into the coarser material. This thin layer also loses water more readily to plants and the atmosphere. The "oily" or "smeary" texture associated with soils developed in volcanic ash was not manifest at either of these sites. 77 Because ash settles through a fluid medium some differ• ential settling might be expected and- would be expressed in the morphology and analyses of soils developed from ash. The particle size analyses (see Table 2) did not reflect differ• ential settling nor was it reflected morphologically at either site. The particle size analyses did, however, indicate a particle size discontinuity at both sites. The analyses of the ash deposit at site 1 shows some stratification. Post deposi• tion redistribution and accumulation is the most likely cause. The proportion of the clay fraction at site 1 compared to that at site 2 indicates that some clay formation has taken place and formation is most intense at the surface. The slightly more favourable weathering environment in the coarser materials below 24 cm is reflected in the clay content at site 1. The fine clay fractions have a similar distribution to the coarse clay. Appreciable clay movement is not indicated as having taken place. The data for the clay content reflects the milder weathering environment at site 2. Dispersion of volcanic ash soils has been reported as being difficult due to surface adsorption characteristics (Ahmad and Prashad, 1970; Swindale, 1969). Sonic dispersion is commonly used on these soils as a standard technique. For comparison, selected samples were sonically dispersed in this study. The technique did not give any better dispersion within the range of particle sizes being measured. Table 2. Selected physical analyses of the- study sjtes 15 bar Water Bulk Hor i zon Depth Sand Silt Clay Fine clay Content density cm g/cm Site 1 Ah 0 - 7.5 56.4 26.4 17.2 10.9 19.7 - Bml 7.5 - 12.5 71 .8 19.4 8.8 8.8 5.4 0.88 Bm2 12.5 - 23 52.3 46.5 1 .2 1 .3 3.3 0.84 Bm4 24 - 29 77.0 15.1 7.9 7.1 6.6 0.67 CB 29 - 36 75.2 17.9 6.9 3.4 8.8 0.75 II Bhfb 36 - 41 32.9 45.9 21.3 13.6 15.0 ••- il Bfb k\ - 46 40.3 47.0 12.8 5.1 10.8 - II BCb 46 - 54 54.2 33.6 12.3 6.0 9.7 - II CBb 5k -104 55.3 34.5 10.2 6.6 10.3 1.48 Site 2 Ah 0 - 11 70.2 27.9 1 .9 0.3 3.6 0.70 Cl 1 1 - 25 91.6 7-3 1 .1 0.3 1.2 0.82 b C2 25 - 48 90.3 8.6 1 .1 N.D. J.l 0.69 II Bmb 48 - 61 52.5 43.8 3.6 0.3 4.2 1.37 II BCb 61 - 86 55.7 39-6 4.7 1 .2 4.2 - If CBb 86+ 60.2 34.7 5.1 2.2 4.7 a% of total clay N.D. - not detectable 79 The values for 15 bar water content are not high for the ash derived soils. With soils dominated by crystalline clays the 15 bar water content is about 0.4 times the clay content (Cortes and Franzmeier, 1972). Higher values are due to poor dispersion or water retention by inorganic gels and/or organic matter. A high correlation (at 1% level of significance) was found with organic matter and clay content. As pointed out by Swindale (1969) when the water content of ash soils is expressed on a volume basis the values approach those of other soils. The 15 bar water content of the soils developed in ash does not indicate a high content of amorphous material or a high degree of weathering. The bulk density values of the ash materials range between 0.67 and 0.88. The low values are the result of the porous nature of the ash. The more porous the volcanic material generally the lower the bulk density. Japanese workers (Japanese Government, 1964) report ranges of bulk density from 0.45 to 0.90 with values tending to increase with weathering and especially where significant amounts of primary minerals are included in the erupted material. The pH values in water (see Table 3) ranged between 3.9 and 6.6 in the ash derived soils and between 5.5 and 6.9 in the paleosols. The lowest pH values were obtained from those horizons with the greatest content of organic matter in both the ash soils and paleosols. A high degree of correlation (1% level of significance) existed between pH and organic matter for the ash derived soils and paleosols when their data were examined separately. The correlation was not as significant 80 when the data was examined as a whole. This could be explained as partly due to the influence of the overlying ash and to the different relationships between the organic matter and the different parent materials with depth. The pH measured in CaCl2 is between 1.2 to 0.7 of a pH unit lower than that measured in water. These differences are similar to those obtained for non-ash soils. In some Japanese and Hawaiian soils the pH measured in KC1 was greater than that measured in water when the pH of the latter was greater than 6 (Soil Survey Staff, 1960, p. 152; Japanese Government, 1964, pp. 103, 110). The soils in this study did not exhibit this character• istic (unpublished data). The values for pH and base satura• tion were highly correlated (1% level of significance). The pH values of the ash derived soil at site 1 were higher than might be expected when the percent base saturation is considered. Many Pacific coast soils of the United States and Canada have this characteristic which has been attributed to the presence of allophane and also to the retention of salts during cation- exchange capacity determinations (Clark, 1964). It is reported (Birrell, 1964; Swindale, 1969; Japanese Government, 1964, p. 103) that ash soils with low base saturations generally have relatively higher pH values than is characteristic of most soils. This has been attributed to the high buffering capacity of allophane in the region of the iso-electric point and the high buffering capacity of the polymerized alumina gels. Freshly deposited ash material is generally acidic due to condensed volatiles on the ash surface. Leaching removes these condensed acidic materials and bases are released. The ash Table 3- Selected chemical analyses of the study sites. Organic Oxalate Horizon Depth pjj Matter N.itrogen Phosphorus extractable cm CaCl„ H„0 NaF % % C/N ppm 2 "2^ Site 1 Ah 0 - 7-5 3-9 4,6 9.1 17.85 0.55 18.8 19.8 0.36 0.57 Bmi 7.5 -12.5 4.4 5.1 11.0 3.08 0.12 14.9 14.4 0.27 0.43 Bm2 12,5 -23 4.6 5.4 10.8 1.28 0.05 14.8 13.7 0.12 0.34 Bm4 24 -29 4.5 5.2 10.7 0.70 0,'03 13.7 12.8 0.11 0.20 CB 29 -36 4.3 5.3 10.5 0.40 0.01 23.0 15.0 0.10 0.16 II Bhfb 36 -41 4.6 5.5 10.4 11.49 0.35 19-0 28.0 0.87 1 .20 II Bfb k\ -46 5.0 6.0 10.9 3.81 0.16 13.8 15.0 0.81 1 .20 II BCb 46 -54 5.3 6.1 9.6 0.61 0.05 7.0 5.4 0.28 0.31 II CBb 5k -•104 5.5 6.6 9>5 0,36 0.02 10.5 4.3 0.27 0.13 Site 2 Ah 0 -11 4.9 6.1 10.3 1.52 0.03 29.4 286.1 0.17 0.33 Cl 11 -25 5.5 6.5 9.8 0.29 0.01 17.0 18.6 0.08 0.08 C2 25 -48 5.7 6.6 9.6 0.27 0.01 16.0 29.9 0.08 1.76 II Bmb 48 -61 5.6 6.7 9.3 0.40 0.02 11.5 36.2 0.79 2.00 II BCb 61 -86 5.8 6.9 9.1 0.15 0.01 9.0 19-1 0.44 1 .08 II CBb 86+ 5.9 6.7 9.1 0.12 0.01 7.0 8.8 0.41 1 .24 82 material then becomes more acidic with continued leaching and weathering. Judging from this sequence the ash soil at site 1 has been subjected to more weathering and leaching than site 2, and has reached a more advanced stage of soil development. The pH values obtained in the pH 7.6 NaF solution ranged from 9.1 to 11.0 at site 1 and from 9.1 to 10.3 at site 2. The increase in pH indicates the presence of reactive A1(0H)X. This compound amongst other materials is a constituent of the amorphous weathering products of soil parent materials includ• ing allophane. Podzolic B horizons generally have pH values greater than pH 10.2 (Brydon and Day, 1970). Again the values obtained indicate, along with the clay content, that more weathering had taken place at site 1 than at site 2. The ash materials at site 1 released relatively large amounts of A1(0H)X, though the source horizons did not necessarily have other spodic characteristics. The high value in the IIBhfb horizon of the paleosol at site 1 could be due to the influence of the overlying ash or be the result of weathering iin situ or both. Weathering at site 2 is most intense at the surface. When comparing the ash soils to the paleosols, the ash materials appear to release relatively more A1(0H)X than the non ash materials. Both the ash soil and the paleosol at site 1 have relatively high organic matter contents when compared to the soils at site 2. The differences are largely due to vegetative and climatic effects. A significant correlation (1% level) between organic matter content and nitrogen, C.E.C., pH-dependent C.E.C., exchangeable Al, Mg, K and 15 bar water content occurred in the 83 ash soils. In the paleosols a significant correlation (1% level) existed between organic matter and nitrogen, pH in H^O and CaCl2, base saturation and exchangeable Al. This reflects the greater significance of organic matter in relation to the colloidal properties of the ash soils, whereas the higher clay content of the paleosols reduces the significance of the organic matter in relation to their colloidal properties. The organic matter content of volcanic ash soils is generally greater than that of non ash soils and it has been found to vary with the maturity of the soil. The organic matter content generally increases with weathering and allo- phane content and then decreases with increasing maturity and crystallization of the amorphous material. With increase in allophane content it has been found that organo-metallie complexes are formed that are resistant to microbial decomposi• tion. Al-organic complexes were found to be particularly resistant to microbial activity. These compounds tend to accumulate. The higher organic matter content of ash soils is also the result of their greater fertility and water- holding capacity resulting in increased growth (Kobo, 1964; Martini, 1969). The soils at site 1 have greater N contents than those at site 2 though the C/N ratios are similar. The available nitrogen content in ash soils tends to be low because of the resistance of the organic matter to microbial decomposition. At site 1 the effects of climate also tend to reduce biologic activity. The C/N ratios in the ash soils range from 13 to 29. 84 In ash soils C/N ratios tend to be higher than in corresponding mineral soils again due to the inhibition of organic matter breakdown and increased plant growth (Martini, 1969; Birrell, 1964). The available phosphorus content ranged from 28.0 to 4.3 ppm at site 1. At site 2 available phosphorus ranged from 286.0 to 8.8 ppm. The highest values of available P, at each site, were obtained from those horizons with the greatest amount of organic matter. The soil at site 2, the least developed of the two soils, had relatively more available phosphorus. In the ash soils the available phosphorus content was within the range common to ash soils developed from similar ashes (Bornemisza and Morales, 1969; Martini, 1969). With increased weathering and content of amorphous materials ash soils tend to fix increas• ing amounts of phosphorus. Most fixation is associated with the formation of insoluble aluminum and iron phosphates (Swindale, 1969; Japanese Government, 1964, pp. 107-108). The lesser amount of phosphorus at site 1 indicates a greater content of amorphous material and possibly aluminum at this site. The greater amounts of available P in the horizons with the most organic matter indicates some of the phosphorus was organically complexed in an available form that was unavail• able for complexing with aluminum and also some of the aluminum was organically complexed preventing it from complexing with phosphorus. The laboratory criterion for defining podzolic B horizons requires that the oxalate extractable Fe + Al exceeds the IC horizon by 0.8% and the ratio of organic matter to oxalate Table 4. Exchange properties of the study sites „ . _ , C.E.C. Base Exchangeable cations pH Exchangeable Horizon Depth meq/ Satn. ! decendent K cm lOOg % Ca Mg K Na CEC aluminum meq/lOOg Site 1 Ah 0 - 7.5 25-31 10.91 1.77 0.61 0.34 0.04 15.4 1.67 Bml 7.5 -12.5 5-95 2.07 N.D. 0.08 0.03 0.01 5.0 0.36 Bm2- 12.5 -23 2.88 0.23 0.23 0.08 0.02 0.03 1 .8 0.18 Bm4 24 -29 2.69 11.52 0.23 0.05 0.02 0.01 1.8 0.12 CB 29 -36 3.06 10.46 0.23 0.05 0.02 0.02 1.1 0.1 1 II Bhfb 36 -41 28.53 25.10 6.30 0.72 0.05 0.09 15.4 0.55 II Bfb k\ -46 20.94 42.26 7-70 1.03 0.05 0.07 8.5 0.13 II BCb 46 -54 24.19 87.31 17.78 3.22 0.05 0.07 5.3 0.08 II CBb 54 -104 27.47 92.36 21 .34 3.94 0.04 0.05 2.8 0.08 Site 2 Ah 0 -11 5.68 35.04 1 .61 0.19 0.17 0.02 3.2 0.11 Cl 1 1 -25 2.25 36.00 0.71 0.03 0.06 0.01 0.5 0.06 C2 25 -48 2.97 29.97 0.77 0.06 0.05 0.01 1 .0 0.06 II Bmb 48 -61 6.11 61.54 3.27 0.20 0.26 0.03 2.5 0.06 II BCB 61 -86 5.95 85.71 3.04 1.73 0.26 0.07 0.2 0.06 II CBb 86+ 6.22 93.25 2.63 2.88 0.24 0.05 0.7 0.06 86 extractable Fe be less than 20 (C.S.S.C., 1970). Only the II Bhfb and II Bfb horizons in the site 1 paleosol meet these and the morphological requirements. In addition these horizons have pH values below pH 5.5 in CaCl^ and greater than 10.2 in NaF, pH-dependent C.E.C.'s greater than 8.0 meq/100 g and oxalate extractable Al values of greater than 0.6%. These are further characteristics associated with podzolic B horizons. With the exception of the II CBb horizon of the site 1 paleosol the Al extractable values equal or exceed those of Fe. Translocation of Fe or Al does not appear to have taken place though the paleosol Al values are high. The extractable Fe and Al values of these soils are discussed in a subsequent paper (Sneddon, 1973c). The C.E.C. of the ash soils (see Table 4) ranged from 25 to 2 meq/100 g and was highly correlated (1% level of signifi• cance) with organic matter, pH-dependent C.E.C., exchangeable aluminum and clay content. The C.E.C. of the paleosols ranged from 28 to 20 at site 1 and was about 6 at site 2. Correlation at the 1% level of significance was with the clay content in the paleosols. The high degree of correlation of C.E.C. with organic matter in the ash soils indicates a dominance of organic exchange sites. In the paleosols, exchange sites appear to be associated more with the clays. Both the ash soils and the paleosols appear to have a slightly higher C.E.C. than might be estimated from their clay and organic matter contents. 87 Difficulties in reaching exchange equilibria are sometimes experienced with ash soils due to the internal porosity of the ash fragments. Artificially high C.E.C. values are also due to the pH dependent nature of the charges on organic matter and amorphous material. This will result in lower base saturations and higher than expected pH values being realized. Several authors have supported the more realistic and useful calculation of C.E.C. by the summation of exchangeable hydrogen, aluminum and bases (Birrell, 1964; Martini, 1969 and Swindale, 1969). The standard NH4OAc method of C.E.C. determination was followed in this study to determine the characteristics of ash soils relative to other soils in the area. Base saturation in both ash soils was much lower than in either of the associated paleosols. The base saturation of the ash soil at site 2 was higher than that at site 1 reflecting the stronger leaching at the latter site. Calcium was the most abundant exchangeable cation followed by Mg. In the ash soils the exchangeable K content exceeded the Na. In the paleosols the geologic origin of the parent materials accounts for the slightly greater amount of exchange• able Na over K at site 1 and the fact that at site 2 the K content exceeds that of Na by 5 to 7 orders of magnitude. The distribution of bases in the soil with depth is a function of the relative amounts of cations weathered from the parent material and subsequent transferrals by leaching. Countering the downward leaching effect is nutrient cycling by plants and to a lesser extent, in this situation, the evaporation of capillary solutions at the surface. 88 The pH-dependent C.E.C. of soils has been correlated with organic matter and amorphous sesquioxides (Clark ejb al. , 1967; Kobo, 1964). The pH-dependent values of site 1 ranged from 15.4 to 1.1 meq per lOOg and at site 2 from 3.2 to 0.6 meq per lOOg. In the two ash soils the values were correlated (1% level of significance) with organic matter exchangeable Al and clay, in decreasing order of signifcance. In the paleosols the values were correlated (1% level of significance) with organic matter, clay, exchangeable Al and fine clay, in decreasing order of significance. Though clay content was highly correlated at both sites it was more significant in the paleosols where the fine clay was also significant. Exchange sites originating in the organic fraction and the low clay contents of the ash soils account for their greater pH- dependent C.E.C. correlation with organic matter when compared to the paleosols. The correlation with exchangeable aluminum indicates the significance of the cation in soils and in exchange reactions in particular. When pH-dependent C.E.C. is taken into account base saturation values are much higher. These values possibly give a better indication of the natural situation than when the results are expressed on the basis of determinations using buffered solutions that do not approach the natural situation. The exchangeable aluminum values were significantly correlated (at 1% level) with organic matter. This reflects the influence of organic matter on the exchange capacity of these soils. The more weathered soil at site 1 contained more exchangeable aluminum than site 2. Horizons with lowest 89 pH values tended to contain the most exchangeable Al. This is related to the increased solubility of Al at low pH. with increasing pH, Al decreased. Horizons that were richer in organic matter tended to slightly higher exchangeable Al values. This was probably due to the release of organically complexed aluminum. Volcanic ash soils exhibiting similar values and relationships have been discussed by Igue and Fuentes (1972). CONCLUSIONS Soils derived from volcanic ash are of limited extent in Canada. They are of local significance in the southwest Yukon, in the vicinity of Mount Edziza and the Bridge River area in British Columbia. As indicated by Sneddon (1973a) many soils in western Canada have been influenced by volcanic ash to varying degrees. A wide range of bioclimatic conditions exist in western Canada. The influence on soil development of these different conditions is correspondingly wide. Soils developed from volcanic ash occur within a more limited range of conditions. The soils in this study have developed in two different bio• climatic zones; a) continental subhumid to humid, interior Douglas fir and b) continental cold, alpine. Soil development was most strongly expressed in the latter environment. The parent material of the two ash soils in this study consists of approximately 2,400 year old Bridge River ash that has been described as dacitic. The depths of pyroclastic material 90 was limited, 36 and 48 cm, at the study sites. The ash parent material has a weathering potential similar to the feldspars which is further enhanced by its greater surface area compared to other materials within the same particle size range. The ash soil at site 1 was an A, (B), C Alpine Dystric Brunisol. The surface mineral horizon had a very friable weak coarse to medium granular structure. With increasing depth the structure became finer and below 24 cm structure was absent. Colors ranged from very dark brown at the surface to yellow in the lowest ash horizon (CB). The ash soil at site 2 was a shallow A, C, Orthic Regosol. The light gray ash showed little color change in the A horizon which had a friable weak fine granular structure. The C hori• zons showed little pedogenic change except for the C2 horizon which was slightly mottled due to the unique water retention properties of the vesicular coarse sand sized particles. The morphological expression of these soils indicates that soils maturing in Bridge River ash initially develop a very friable weak fine granular structure which evolves coarse and medium granular. Soil color changes from the light gray of the parent material to yellow. With increase in organic matter the colors become more brown. The pedogenic youth of these ash soils was reflected in their physical properties. Low bulk densities were inherited from the parent material and 15 bar waterholding capacity and clay content were low. 91 The source of most of the colloidal properties of these youthful volcanic ash soils lies in the organic matter fraction. The amount of amorphous Al(OH) that was indirectly measured was more than would be expected from similar non-podzolic, non-ash derived soils. The presence of free Al can result in the inactivation of available phosphorus and in the inhibition of the microbial decomposition of organic matter. This can result in a buildup of organic matter in the soil with attendant increase in properties imparted to the soil by organic matter. Aluminum has influenced many of the properties of these soils including those examined in this study. The physical and chemical properties of the soils in this study indicate that the physical properties of ash soils are initially inherited from the parent material. The colloidal and chemical properties are initially imparted by organic matter with some influence from the weathering products of the ash and especially aluminum. Ash soils from more intensive weathering environments were not examined but it is expected that with increasing age and development physical properties would develop that are more pedogenic in origin, and chemical and colloidal properties would develop that, to a greater extent, would be imparted by the weathering products of the ash. Shallow additions of Bridge River ash to soils will similarly influence soil properties to varying degrees as described above, depending on the biogeoclimatic environment of the area of deposition and depth of material added. 92 REFERENCES AHMAD, N. and PRASHAD, S. (1970). Dispersion, mechanical composition, and fractionation of west Indian volcanic yellow earth soils (andepts). The Journal of Soil Science 21, 63-71. ATMOSPHERIC ENVIRONMENT SERVICE, DEPARTMENT OF THE ENVIRONMENT (1972). Temperature and precipitation, 1941-1970, British Columb ia. Ottawa. BIRRELL, K.S. (1964). Some properties of volcanic ash soils. World Soil Resources Reports 14, 74-81. FAO, Rome. BORNEMISZA, E. and MORALES, J.C. (1969). Soil chemical character• istics of recent volcanic ash. Soil Science Society of America Proceedings, 33, 528-530. BRAYSHAW, T.C. (1965). The dry forest of southern British Columbia. In_ "Ecology of Western North America." (V.J. Krajina, Ed.), Vol. 1, pp. 65-75. University of British Columbia, Vancouver . BRYDON, J.E. and DAY, J.H. (1970). Use of the Fieldes and Perrot sodium fluoride test to distinguish the B horizons of podzols in the field. Canadian Journal of Soil Science 50, 35-41. CANADA SOIL SURVEY COMMITTEE (1970). The system of soil classification for Canada. Canada Department of Agriculture, Ottawa. CARROLL, D. (1970). "Rock Weathering." Plenum Press, New York. CLARK, J.S. (1964). Some cation-exchange properties of soils containing free oxides. Canadian Journal of Soil Science 44, 203-211. CLARK, J.S., MCKEAGUE, J.A., and NICHOL, W.E. (1966). The use of pH-dependent cation exchange capacity for characterizing the B horizons of brunisolic and podzolic soils. Canadian Journal of Soil Science 46, 161-166. CLARK, J.S., GREEN, A.J., and NICHOL, W.E. (1967). Cation exchange and associated properties of some soils from Vancouver Island, British Columbia. Canadian Journal of Soil Science 47, 187-202. CORTES, A. and FRANZMEIER, D.P. (1972). Climosequence of ash derived soils in The Central Cordillera of Columbia. Soil Science Society of America Proceedings 36, 653-659. 93 DAY, P.R. (1965). Particle fractionation and particle size analysis. In "Methods of Soil Analysis." (C.A. Black, Ed.). Part 1, pp. 545-567. American Society of Agronomy. Madison, Wisconsin. EGAWA, T. (1965). Mineralogical properties of volcanic ash soils in Japan. World Soil Resources Report 14, 89-91. FAO, Rome. FAO (1964). Meeting on the classification and correlation of soils from volcanic ash. World Soil Resources Report 14. FAO, Rome. FIELDES, M. and SWINDALE, L.D. (1954). Chemical weathering of silicates in soil formation. New Zealand Journal of Science, Tech. B. 36, 140-154. HANSEN, H.P. (1947). Postglacial forest succession, climate and chronology in the Pacific Northwest. Transactions of the American Philosophical Society 37, 1-130. HARWOOD, M.E. and YOUNGBERG, C.T. (1969). Soils from Mazama ash in Oregon: identification, distribution and properties. In "Pedology and Quaternary Research." (S. Pawluk, Ed.) pp. 163-178. University of Alberta, Edmonton. HEUSSER, C.J. (1952). Pollen profiles from southwestern Alaska. Ecological Monographs 22, 331-352. HOLLAND, S.S. (1964). "Landforms of British Columbia, a physio• graphic outline." British Columbia Department of Mines and Petroleum Resources. Bulletin Number 48, Victoria, B.C. IAIAS (1969). Panel on volcanic ash soils in Latin America. Turrialba, Costa Rica. Training and Research Center of the IAAIS, Turrialba, Costa Rica. IGUE, K. and FUENTES, R. (1972). Characterization of aluminum in volcanic ash soils. Soil Science Society of America Proceedings 36, 292-296. JACKSON, M.L. (1956). "Soil chemical analysis, advanced course." Published by author, Madison, Wisconsin. JAPANESE GOVERNMENT; MINISTRY OF AGRICULTURE AND FORESTRY (1964). Volcanic ash soils in Japan. Tokyo. KOBO, K. (1964). Properties of volcanic ash soils. World Soil Resources Reports 14, 71-73. FAO, Rome. KRAJINA, V.J. (1965). Biogeoclimatic zones and biogeocoenoses of British Columbia. In_ "Ecology of Western North America." (V.J. Krajina, Ed.), Vol. 1, pp. 1-17. University of British Columbia, Vancouver. 94 Leco (1959). Instruction manual for operation of Leco carbon analyzers. Laboratory Equipment Corporation, St. Joseph, Michigan. MARTINI, J.A. (1969). Geographic distribution and character• istics of volcanic ash soils in Central America. In "Panel on volcanic ash soils in Latin America." Section A.5, Turrialba, Costa Rica. MEHRA, O.P. and JACKSON, M.L. (I960). Iron oxide removal from soils and clays by a dithionite-citrate system buffered with sodium bicarbonate. Clays and clay minerals. Proceedings of the 7th National Conference (1958), 317-327. NASMITH, H., MATHEWS, W.H. and ROUSE, G .E. (1967). Bridge River ash and some other recent ash beds in British Columbia. Canadian Journal of Earth Sciences 4, 163-170. OLSEN, S.R. and DEAN, L.A. (1965). Phosphorus. In. "Methods of Soil Analysis" (CA. Black, Ed.) Part 2, 1035-1049. American Society of Agronomy. Madison, Wisconson. SNEDDON, J.I. (1973a). Volcanic ash, its significance and distribution in western Canada. Ph.D. thesis, University of British Columbia, Vancouver, B.C. SNEDDON, J.I. (1973c). The podzolic characteristics of two soils developed in volcanic ash in southwest British Columbia. Ph.D. thesis. University of British Columbia, Vancouver, B.C. SNEDDON, J.I. (1973d). The amorphous and crystalline weathering products of two soils developed in volcanic ash in south• west British Columbia. Ph.D. thesis. University of British Columbia, Vancouver, B.C. SOIL SURVEY STAFF. (1951). Soil survey manual, U.S.D.A. Hand• book number 18. United States Government Printing Office, Washington. SOIL SURVEY .STAFF. (1960). Soil classification, a comprehensive system (7th Approximation). U.S.D.A. Soil Conservation Service, United States Government Printing Office, Washington. SOIL SURVEY STAFF. (1967). Soil survey laboratory methods and procedures for collecting soil samples. Soil Survey investigations report number 1. U.S.D.A., Soil Conserva• tion Service, United states Government Printing Office, Washington. STEVENSON, L.S. (1947). Pumice from Haylmore, Bridge River, British Columbia. The American Mineralogist 32, 547-552. 95 SWINDALE, L.D. (1969). Properties of volcanic ash soils. In "Panel on volcanic ash soils in Latin America." Section B. 10. Turrialba, Costa Rica. WRIGHT, A.C.S. (1964). The "Andosols" or "Humic Allophane" soils of South America. World Soil Resources Reports 14, 9-22. FAO, Rome. u THE PODZOLIC CHARACTERISTICS OF TWO SOILS DERIVED FROM VOLCANIC ASH IN SOUTHWEST BRITISH COLUMBIA INTRODUCTION Iron and Al are weathered from geologic materials during the course of soil formation. These materials reflect the processes of soil formation in their distribution in the soil. Together or individually they influence characteristics of: (a) soil morphology such as colour and structure; (b) soil chemistry such as organic matter content and pH-dependent charge; (c) plant nutrient status, as they complex certain elements and render them unavailable, e.g. phosphorus; and (d) the soil to adsorb certain fractions of anthropic materials, e.g. from municipal wastes. The distribution of Fe and Al in the pedon reflect the type direction and extent of pedogenic processes and may be used as a basis for differentiating certain classes of soils. Over the last few years a number of methods for determining the distribution of Fe and Al in soils have been proposed. As pointed out by Schwertmann (1973), Fe and Al exist in the soil as a continuum between the amorphous and crystalline state. No single method distinctly separates out a single fraction from this continuum but rather separates out a portion to give a measure of the quantity of a fraction within relatively unspecified limits. 97 The various methods of Fe and Al dissolution have been evaluated (Bascomb, 1968; Blume and Schwertmann, 1969; McKeague et al., 1971; Pawluk, 1972 and Schwertmann, 1973). These evaluations are in general agreement and in total conclude: (a) Dithionite citrate bicarbonate extracts most of the pedogenic Fe, Mn and Al, including the organically complexed, the amorphous and some crystallized Fe and Al. (b) Pyrophosphate-dithionite extracts some of the crystal• line as well as the amorphous and organically complexed Fe and Al. McKeague (1967) found pyrophosphate dithionite did not clearly differentiate between crystalline and amorphous forms and Flach, Nelson and Rieger (paper presented at the A.S.A. meetings, Detroit 1969) found results were not reproducible, and both concluded this procedure to be of limited value. (c) Acid ammonium oxalate extracts amorphous Al and Mn and the amorphous aged and gel type hydrous oxides of iron as well as a major portion of the organically complexed Fe. Attention has also been drawn to the fact that in some situa• tions oxalate will extract crystalline forms of Fe (Pawluk, 1972; Schwertmann, 1973). (d) Sodium pyrophosphate at pH 10 extracts amorphous gels and organic complexes of Fe and Al. The podzolic characteristics of soils have also been determined by the measurement of soil properties that are highly correlated with amorphous iron and/or aluminum and their organic complexes. Phosphorus adsorption capacity (Bartlett, 1972), pH-dependent cation exchange capacity (Clark, 1966) and pH in 98 IM NaF (Brydon and Day, 1970) are methods that have been shown to provide useful data for distinguishing podzolic Bf horizons. People working with soils derived from or influenced by volcanic ash (Flach, Nelson and Rieger, paper presented at A.S.A. meetings, Detroit 1969; McKeague e_t al., 1971) have been aware that the weathering products of volcanic ash have led to difficulties in characterizing podzolic B horizons. These weathering products yield more amorphous materials to the soils than degree of soil development indicates or is found in similar soils not affected by ash. The purpose of this study is to evaluate the methods for identifying podzolic B horizons in relation to two previously characterized soils (Sneddon, 1973b) developed in Bridge River volcanic ash and their underlying paleosols, and evaluate the influence of surface additions of this ash on the podzolic characteristics of soils. MATERIALS AND METHODS The soil materials used in this study were those described and sampled by Sneddon (1973b). The following determinations were conducted: the Fieldes and Perrott IM NaF test as described by Brydon and Day (1970), pH was measured after a 1/2 hr using a glass electrode and a pH meter; pH-dependent cation exchange capacity (Clarke et al., 1966), pyrophosphate dithionite (Franzmeier et al., 1965), dithionite citrate bicarbonate (Mehra and Jackson, 1960) and sodium pyrophosphate (McKeague, 1967) extractable Fe, Al, Si and Mn determined by atomic Table 1. Ratio of oxalate to pyrophosphate-dithionite to citrate-dithionite to 0.1 M pyrophosphate extractable Fe, Al, Si and Mn Horizon Depth Fe Al Si Mn cm Si te 1 Ah 0 - 7.5 2.0- 1.1- 3-0-1 .0 1.2-0.8-1 .0-1 .0 2.3-1 .0-1 .0-1 .0 2.6- 1.6- 3.3-1 .0 Bml 7.5" 12.5 3.0- 1.7- 2.4-1 .0 2.4-1.1-0.9-1 .0 1 .4-1 .3-1 .0-1 .0 8.0- 6.7-10.8-1 .0 Bm2 12.5- 23 4.0- 3-7-52.7-1 .0 4.6-1.8-1 .2-1 .0 1 .9-1 .9-1 .3-1 .0 5.2- 2.6- 5-6-1 .0 Bm4 24 - 29 5.5- 8.5- 4.0-1 .0 1.2-3.2-1 .1-1 .0 1.1-2.3-1 .2-1 .0 28.8- 12.0-31 -3-1 .0 CB 29 " 36 5 - 1.5- 2.5-1 .0 1.3-1 .3-1.1-1 .0 1.0-1.3-0 .8-1 .0 24.8- 22.0-25.0-1 .0 HBhfb 36 - k\ 2.7- 1.7- 3.9-1 .0 1.6-1.0-1.0-1 .0 2.0-1.3-0 .8-1 .0 5.8- 3.1- 8.0-1 .0 IlBfb k\ - kG 4.1- 2.2- 5.4-1 .0 2.7-1.8-1.6-1 .0 4.2-2.1-1 .2-1 .0 24.8- 2.4-18.8-1 .0 IIBCb kG - 5k 4.7- 4.7-15.5-1 .0 3.9-1.8-2.9-1 .0 3.1-1 .3-1 .5-1 .0 32.0- 3.8-40.9-1 .0 IICBb 5k - 104 6.8- 7.5-29.5-1 .0 1.9-1.6-2.1-1 .0 0.5-1.1-1 .1-1 .0 91.4- 5.3-90.4-1 .0 Site 2 Ah 0. - 11 1.5- 1.2- 2.5-1 .0 1.3-1.0-1 .3-1 .0 1.1-1.1-1 .7-1 .0 0.3- 1.5- 3.0-1 .0 Cl 11 - 25 4.0- 2.0- 3.0-1 .0 1.6-1.6-2.0-1 .0 0.5-1.0-1 .3-1 .0 5.0- 1 .7- 3.3-1 .0 C2 25 - 48 2.7- 1.3- 2.7-1 .0 22.0-1.5-2.3-1 .0 1.1-1.1-1 .8-1 .0 3.3- 2.3- 2.3-1 .0 IIBmb 48 - 61 6.1- 2.2- 6.3-1 .0 18.2-1.4-1 .8-1 .0 0.6-1 .0-1 .1-1 .0 20.2- 5.0-17.8-1 .0 IIBcb 61 - 86 2.8- 1.5- 3.5-1 .0 9.0-0.9-1.1-1 .0 0.3-0.7-0 .9-1 .0 • 8.3- 4.0- 8.0-1 .0 IICBb 86+ 20.5- 12.0-24.5-1 .0 24.8-2.2-2.0-1 .0 0.7-1.3-1 .6-1 .0 18.6- 9.0-17-6-1 .0 100 absorption spectrophotometry7 phosphate sorption capacity by 3 methods using KH2P04 (Bartlett, 1972), Ca(H2P04)2 following the method of Mehlich (1960) using original sample material and KH2P04. In the latter method 2.5 g of <0.5 mm (ground) soil was placed in a 100 ml test tube, to which 50^mol P/g of 0.01 m solution of KH2P04 in 0.01 M KC1 was added and made up to 50 ml with 0.02 M KC1. One drop of toluene was added and the mixture was shaken for 12 hrs and filtered. In all three P sorption methods. Pi, P2 and P3, the P was deter- mind by the vanadomolybdophosphoric yellow method (Jackson, 1958, p. 151) on a control solution without soil and on the test solutions. The sorption values were determined by difference. Correlation coefficients were determined at the U.B.C. computing centre, using the U.B.C. TRIP subroutine program. RESULTS AND DISCUSSION Of the four extracting agents used the pyrophosphate had the least dissolution effect (see Table 1). While no attempt was made to determine which fraction was extracted the horizons with the most organic matter (0.7 percent or more) release in order of abundance Al>Si^Fe^Mn. Horizons with less organic matter released more Si than Al followed by Fe and Mn. The pyrophosphate extractable Fe and Al was significantly correlated (1% level) with organic matter and related properties such as peroxide extractable Si, Al and Fe (for peroxide extractable values see Sneddon 1973d). This supports the findings that 101 organically complexed Fe and Al are released by pyrophosphate. The pyrophosphate extractable Fe plus Al was found to differ• entiate between podzolic B horizons of the site 1 paleosol and the Bm horizons and horizons developed in ash of the other soils. The Ah horizon at site 1 yielded enough Fe and Al to meet both the oxalate and pyrophosphate criteria for podzolic B horizons (see Table 6) (C.S.S.C., 1969; C.S.S.C., 1973). Both methods extracted similar amounts from the Ah horizon at site 2. This is not unexpected in terms of the amount of organic matter and weathering that takes place in surface horizons relative to the rest of the pedon. Acid ammonium oxalate extracted more aluminum from the soils than any of the other methods, slightly less iron and equivalent amounts of Mn to citrate dithionite. The order of abundance of extracted elements was Al > Fe 2r si > Mn. The values of Al extracted by acid ammonium oxalate give further evidence of the difficulties associated with podzolic B criteria based on this method. Claims have been made that the criteria are rendered ineffective by the presence of volcanic ash. The data collected here indicate that large amounts of Al were extracted from the site 2 paleosol that did not contain noticeable amounts of ash. Aluminum could have been leached from the overlying ash soil. However, the morphology and other data collected in this study give no indication that leaching of Al accounts for these values. Significant correlations (1% level) occurred between organic matter and oxalate extractable Fe and Si in the ash soils, otherwise a number of significant correlations were obtained Table 2. Percent Fe and Al extracted by four methods and phosphate sorption by three methods on the fine earth fractions of the study sites 0 IM Phosphate Sorption Horizon Depth Oxalate P-D i thioni te C-DIthioni te Pyrophosphate p] p2 cm Fe % Al % Fe % Al % Fe % Al % Fe X Al % P ppm P ppm P ppm Site 1 Ah 0 - 7.75 0.36 0.57 0.20 0.40 0.54 0. 48 0.18 0.48 51 .8 1212.2 842.5 Bml 7.5- 12.5 0.27 0.43 0.16 0.40 0.22 0. 35 0.09 0.37 50 .7 885.0 479.1 Bm2 12.5- 23 0.12 0.34 0.11 0.35 1 .58 0. 23 0.03 0.20 48 .4 574.7 396.5 Bm4 24 - 29 0.11 0.20 0.17 0.55 0.08 0. 18 0.02 0.17 32 .2 376.3 263.3 CB 29 - 36 0.10 0.16 0.03 0.15 0.05 0. 13 0.02 0.12 30 .2 123.5 212.1 IIBhfb 36 - k] 0.87 1 .20 0.54 0.75 1 .24 0. 75 0.32 0.75 52 .4 1487.6 945.4 IIBfb 41 - 46 0.81 1 .20 0.44 0.79 1.13 0. 73 0.20 0.45 51 .8 1418.3 795.6 IIBCb kG - 5k 0.28 0.31 0.28 0.14 0.93 0. 23 0.06 0.08 41 .4 395.7 310.2 IICBb 5k -104 0.27 0.13 0.30 0.11 1.18 0. 15 0.04 0.07 31 .3 266.8 256.3 Site 2 358 Ah 0 - 11 0.17 0.33 0.13 0.25 0.27 0.33 0.11 0.25 40.3 483.8 .8 Cl 1 1 -25 0.08 0.08 0.04 0.08 0.06 0.10 0.02 0.05 8.0 118.0 131.3 C2 25 " 48 0.08 1.76 0.04 0.12 0.08 0.18 0.03 0.08 14.0 38.5 141.3 IJBmb 48 - 61 0.79 2.00 0.29 0.15 0.82 0.20 0.13 0.11 40.3 51.6 314.5 HBCb 61 - 86 0.44 1 .08 0.24 0.11 0.56 0.13 0.16 0.12 30.2 225.3 222.3 IICBb 86+ - 0.41 1 .24 0.24 0.11 0.49 0.10 0.02 0.05 30.2 180.3 207-2 Table 3. Mn and Si extracted by the four methods used to extract Fe and Al Hor i zon Depth Ammon ium Oxa late Pyrophosphate D i th ion i te C i trate Dithioni te 0.1M Pyrophosphate cm Mn ppm Si ppm Mn ppm S i ppm Mn ppm S i ppm Mn ppm S i ppm Site 1 2000 Ah 0 - 7.5 85.2 4640 52.0 1900 110.0 2000 33.0 Bml 7. 5- 12.5 24.0 2800 20.0 2500 32.5 2000 3.0 2000 Bm2 12. 5- 23 46.4 3000 23.0 3100 50.0 2000 9.0 1600 Bm4 24 - 29 57.6 1360 24.0 3000 62.5 1500 2.0 1300 CB 29 - 36 24.8 1440 22.0 1900 25.0 1250 1 .0 1500 II Bhfb 36 - Hi 179.6 6400 95.0 4100 248.0 2500 31.0 3200 II Bfb k] - 46 770.0 8880 74.0 4440 582.5 2500 31.0 2100 II BCb kG - 5k 256.0 4680 30.0 1900 327.5 2250 8.0 1500 II CBb 5k -]0k 640.0 1200 37.0 2500 632.5 2500 7.0 2300 Si te 2 1900 Ah 0 - 11 20 2040 101 2100 210 3250 69 Cl 1 1 - 25 15 880 5 1800 10 2250 3 1800 C2 25 - 48 10 2320 7 2200 7 3500 3 2000 II Bmb 48 - 61 730 1760 180 2800 640 3250 36 2900 II BCb 61 - 86 83 1320 40 2900 80 4000 10 4300 II CBb 86 -100+ 93 1920 45 3400 88 4250 5 2700 o u> 104 but were not interpreted as being meaningful as far as this study is concerned. Pyrophosphate dithionite generally had a greater dissolu• tion effect than pyrophosphate, and a lesser one than oxalate. More Al and Si than Fe were released from the ash soils, while in the paleosols greater quantities of Fe were released, in some cases more than either Al or Si. Again significant correlations were obtained which were not interpreted as being meaningful from the point of view of this study. Dithionite citrate bicarbonate was most effective in the dissolution of Fe. It extracted comparable amounts of Mn and Si, and less aluminum than oxalate. A differentiation could be made between the podzolic B horizons and the other horizons if only Al was considered as it showed a relative accumulation in these horizons. Iron, on the other hand, exhibited a more uneven distribution with relatively more being extracted from the paleosols than the ash soils. The ratio of oxalate to dithionite extractable Fe (see Table 6), gives a relative measure, with some limitations, of the degree of aging or crystallinity of the free Fe oxides (Blume and Schwertmann, 1969). Except for the surface horizons and Bm 2 horizon at site 1 the two ash soils exhibit a minimum of aging or crystallinity of the free iron oxides. This is probably associated with the strong influence of organic matter in these soils, resulting in most of the free sesquioxides being associated with organic matter. The weight of published evidence indicates that, without further study, the ratio values of greater than 1 should not be taken to indicate that oxalate extracts more Fe than dithionite in a single extraction. The Table 4. Correlation coefficients between the three methods of P sorption, PI, P2 and P3 and other soil properties at the \% level of significance in two ash soils and their underlying paleosols Sorption Method PI P2 P3 Ash Soilsd 3 P2 0.8603 Pyrophosphate Ala 0.9784 Amorphous material' 0.9774 P3 0.8186 P3 0.9699 P2 0.9699 a Amorphous material'3 0.8501 Amorphous material'3 0.9585 Pyrophosphate Al 0.9631 a C a 0.9526 Oxalate Fe 0.9497 pH in CaCl0 0.8216 Oxalate Fe z 0.8078 Citrate-dithionite Ala 0.9271 Citrate-dithionite Ala 0.9332 pH in H_0C Pyrophosphate-d i th ion i te Fea 0.8669 N i trogen 0.9230 0 PI 0.8603 Organic matter 0.9146 Oxalate Sia 0.8474 C.E.C.C 0.9056 Pyrophosphate Fea 0.8495 Oxalate Sia 0.9039 a N i trogenc O.8383 Pyrophosphate Fe 0.8943 Organic matterc 0.8193 Peroxide Al*3 0.8609 3 C.E.C.0 0.8030 Peroxide Fe 0.8531 Peroxide Si'3 0.8466 PI 0.8186 Pyrophosphate-di thionite Fea 0.8022 (conti nued) Table 4 - continued Sorption Method PI P2 P3 Paleosolse a C i trate-d i thioni te Ala 0.9368 Citrate-dithionite Ala 0.9814 Citrate-dithionite Al 0.9916 a P3 0.9244 Pyrophosphate-dithionite Ala 0.9806 Pyrophosphate-dithionite Fe 0.9840 pH in CaC^ 0.9155 Amorphous material^ 0.9768 Pyrophosphate dithionite Al 0.9798 a Base saturation0 0.9110 P3 0.9722 Pyrophosphate Al 0.9734 Oxalate Sia 0.9071 pH in NaF 0.9464 P2 0.9722 pH in NaF 0.8999 Pyrophosphate-dithionite Fea 0.9419 Amorphous material 0.9627 0 Pyrophosphate-dithionite Ala 0.8992 Pyrophosphate Ala 0.9339 N i trogen 0.9505 0 Pyrophosphate-dithionite Fe 0.8876 Oxalate Sia 0.9113 Base saturation 0.9448 0 c pH in rL0° 0.8867 N i trogen 0.9086 0.9352 pH i n CaC1^ Amorphous material 0.8832 pH in CaC12° 0.9064 PI 0.9244 0.9127 P2 0.8724 pH in H20° 0.8803 Organic matter Pyrophosphate Ala 0.8429 PI 0.8724 pH in NaF 0.9178 0 0 N i trogen 0.8338 Organic matter 0.8568 pH in H20° 0.8897 . c 0.8513 Oxalate Sia 0.8662 Base saturation Clay0 0.8479 Pyrophosphate Fea O.8638 Peroxide Ala b 0.8556 Clayc 0.8351 a) Extractable b) Determined values reported by Sneddon 1973d c) Determined values reported by Sneddon 1973b d) Significant p £0.01, correlation coefficient + 0.798 e) Significant p < 0.01, correlation coefficient + 0.834 107 low amounts of extractable Fe suggest that these values may be due to instrumental limitations relative to the two extracting solutions, though the extracting efficiency of the oxalate solution is probably greater because of the presence of magne• tite and its oxidation products in the ash materials. In the paleosols the values at site 1 are within the expected range from a morphological evaluation. At site 2 the values are higher than expected. This indicates that either (a) limited amounts of primary crystalline Fe are extractable by dithionite or (b) the extracting efficiency of the oxalate solution is quite high in these materials. The values for phosphate sorption indicated that method Pi sorbed the least phosphorus, methods P2 and P3 sorbed similar amounts. Method P2 sorbed the most in the more weathered materi• als, mostly at site 1, while method P3 sorbed more in the less weathered materials, mostly at site 2. The sorption values were highest in the podzolic B horizons. They showed a tendency to decrease with depth, increasing in those horizons exhibiting increases in sesquioxides. The significant correlations (at 1% level) indicated in Table 4 give some indications of the sorp• tion relationships to extractable sesquioxides and other soil properties. Correlations with sorption method Pi were of less signifi• cance (at 1% level) and fewer in number than with methods P2 and P3. Considering the significant correlations (at 1% level) in the ash soils, it is evident that the amorphous materials, and certain extractions of the amorphous to crystalline continuum, and organic matter and some of its associated properties, are related to the sorption of P. 108 The sorption of P is associated with amorphous Al and to a lesser extent Fe (Bartlett, 1972; Fassbender; 1969; Galindo et al., 1969; Swindale, 1969). The more amorphous and solublized Al present the greater the sorption of P. It has been proposed (Harter, 1969) that initially P is bonded to organic matter and is subsequently transformed into less soluble forms. The correlations of organic matter with P sorption capacities do not contradict this proposal, though mineral organic complexes are most likely involved to some degree in initial P sorption as well. Phosphorus sorption is reduced by Si (Cloos e_t al., 1968; Birrell, 1964). With increasing amounts of Si the hydroxy- aluminum complexes with Si reducing the amount of Al available for sorption of P. As pointed out by Hsu (1965), in the sorp• tion and precipitation of P much depends on the forms of Al and Fe present and the physical chemical relationships prevailing in the soil. Williams e_t a_l. (1958) in their study found oxalate extractable aluminum gave the most significant overall correla• tion with P sorption. The degree of correlation varied with soils on different parent materials and in the case of granite they found citrate dithionite extractable Al was more signifi• cant. They considered that the sorption activity was being carried out by Al and Fe occurring mainly as organic complexes. In this study citrate dithionite extractable Al was the most significant extraction in the paleosols while pyrophosphate extractable Al was the more significant in the ash soils. These extractions were only more significant to a degree as other extractions were also highly significant. They do 109 reflect the stronger influence of organic matter in the relatively young ash soils compared to the paleosols. The sesguioxides in the paleosols may have had the opportunity to partially crystallize rendering them slightly less available for some extractions. The values obtained for pH measured in NaF (see Table 6) did not correlate with any other values determined on the ash soils. Significant correlations (1% level) occurred in the paleosols between pH in NaF and amorphous material (values reported in Sneddon, 1973d), citrate dithionite and pyrophos• phate dithionite extractable Al, oxalate extractable Si, Pi, P2 and P3 phosphate sorption values and pyrophosphate dithionite extractable Fe. The difference in pH between that measured in H20 or CaCl2 and NaF is due to the presence of reactive A1(0H)V and to a lesser extent Fe(0H)„. This accounts for the significant correlations with extractable Al, phosphate sorption values and amorphous material content. The correla• tions with extractable Si and Fe are possibly due to propor• tional extractions of those elements with Al extractions. Contrary to the findings of Brydon and Day (1970) no significant correlation was found with oxalate extractable Al. Soil materials yielding greater than 1% oxalate Al did not yield pH values greater than 11.0. The reasons given by Brydon and Day (1970) for the nonlinearity of their plot of Al vs. pH apply equally to the results reported here. The NaF test, in this study, did not distinguish between podzolic B horizons and those developed in volcanic ash. 110 Table 5. Correlation coefficients between pH-dependent C.E.C. and other soil properties at the \% level of significance in two ash soils and their underlying palesols Paleosolsc Ash soi1sd Organic matter*3 0.9670 Organic matter*3 0.9830 Pyrophosphate-dithionite Fea 0.9641 P sorption method 3 0.9590 Pyrophosphate Ala 0.9564 g 0.9160 Pyrophosphate Fe P sorption method 3 0.9480 Pyrophosphate Al 0.9058 Clayb 0.9409 P sorption method 2 0.892 Citrate dithionite Ala 0.9141 Citrate dithionite Ala 0.891 P sorption method 2 0.9130 Clayb 0.872 Pyrophosphate dithionite Ala 0.8760 Oxalate Sia 0.8520 P sorption method 1 0.8750 Fine Clay 0.8839 a) Extractable b) Determined values reported by Sneddon 1973b c) Significant p < 0.01 , correlation coefficient + 0.834 d) Significant p < 0.01, correlation coefficient +_ 0.798 Table 6. pH in NaF, pH-dependent C.E.C . and values derived from Fe and Al extractions by oxalate and pyrophosphate in two ash soiIs and their underlying paleospls b pH in {C) pH-dependent ^ Oxalate Fe Pyrophosphate^ Pyrophosphate Oxalate^ Hor izon Depth NaF C.E.C. Di thioni te Fe Fe + Al Fe + Al Fe + Al meq/lOOg % % clay % Site 1 Ah 0 - 7.5 9-1 15.4 0.67 0.66 0.04 0.93 Bml 7.5- 12.5 11 .0 5.0 1 .23 0.46 0.53 0.70 Bm2 12.5- 23 10.8 1.8 0.08 0.23 0.19 0.46 Bm4 24 - 23 10.7. 1.8 1.38 0.19 0.02 0.31 CB 23 ~ 36 10.5 1 .1 2.00 0.14 0.02 0.26 II Bhfb 36 - 41 10.4 15.4 0.70 1.07 0.05 2.07 II Bfb 41 - 46 10.9 8.5 0.72 0.65 0.05 2.00 II BCb 46 - 54 9.6 5.3 0.30 0.14 0.01 0.59 II CBb 54 -104 9-5 2.8 0.02 0.11 0.01 0.40 Site 2 Ah 0-11 10.3 3.2 0.63 0.36 0.19 0.50 Cl 11 - 25 9.8 0.5 1.34 0.07 0.06 0.16 C2 25 - 48 9-6 1.0 1 .00 0.11 0.10 1.84 II Bmb 48 - 61 9.3 2.5 0.97 0.24 0.06 2.79 II BCb 61 - 86 9.1 0.2 0.78 0.28 0.06 1.52 II CBb 86+ 9.1 0.7 0.84 0.07 0.01 1.65 (a) C.S.S.C, 1970. in a Bf and Bhf horizon the oxalate extractable Fe + Al exceeds that of the IC horizon by 0.8%. (b) C.S.S.C, 1973- in a Bf and Bhf horizon the pyrophosphate extractable Fe + Al >0.6% in textures finer than sand and >^ 0.4% in sands. (c) C.S.S.C, 1973- as a field test pH in 1 M NaF > 10.3 for most podzol B horizons. (d) C.S.S.C, 1973. in podzol B horizons the pH-dependent C.E.C. is usually >8 meq/lOOg. 112 With one exception, the site 1 Ah, the pH-dependent C.E.C. values (see Table 6) readily distinguished between podzolic B horizons and those developed in volcanic ash. The values determined on the podzolic B horizons were above the 8 meq/lOOg suggested (C.S.S.C., 1973) as a distinguishing property of these types of horizon. The significant correlations between pH-dependent C.E.C. and other measured soil properties (see Table 5) reflects the influence organic matter and certain fractions of the extract- able sesquioxides have on this characteristic. The site 1 Ah horizon had a number of characteristics that indicated it had more in common with B horizons than A horizons, e.g. P sorption capacity, pyrophosphate extractable Fe and Al. Flach, Nelson and Rieger (paper presented at A.S.A. meetings Detroit, 1969) indicated that the A horizons of andepts in the Pacific Northwest and Alaska released significant amounts of pyrophosphate extractable sesquioxides and had incipient spodic characteristics. Sneddon e_t al. (1972) indicated that in certain environments the podzolic morphology of soils may be masked by accumulations of organic matter. This suggests that many horizons currently recognized as Ah horizons might have more characteristics in common with podzolic B horizons. CONCLUSIONS Of the four methods of extraction of Fe and Al that have been used as a basis for determining the definitive chemical criteria for podzol B horizons, acid ammonium oxalate was found 113 to be least useful. It extracted comparatively large amounts of Al from the samples of the least developed soil at site 2. The other three methods, pyrophosphate, pyrophosphate dithion• ite and citrate dithionite bicarbonate, all highlighted the podzol B horizons and did not yield results that could be mis• interpreted due to the presence of volcanic ash. Of the associated properties, the pH-dependent C.E.C. and phosphate sorption by methods P2 and P3 appeared to be highly diagnostic and significantly correlated with other diagnostic properties. The NaF test did not distinguish the podzolic B horizons and was poorly correlated with other measured parameters. The Pi phosphate sorption properties did correlate with a number of other soil properties, but not with as many or to the same degree of significance as the other two methods. The various extractions of Mn and Si indicated that these elements were responding to pedologic processes but, with the exception of oxalate extractable silica, were not significantly correlated with any other properties. The distribution of extractions of these elements were considered to have limited value for classification purposes. The oxalate extractable Si was significantly correlated with a number of other properties but this was not interpreted as being of direct consequence in this study. The presence of surface additions of Bridge River volcanic ash to soils may influence acid ammonium oxalate extractions and pH values measured in NaF, otherwise it was not found to reduce the value of diagnostic criteria that have been developed to aid in the classification of podzolic soils. 114 Indicated in this study and in the study by Williams e_t al. (1958) is the importance of the geologic parent material. Often soils are compared and studied on the basis of their morphologi• cal expression and results are interpreted on the basis of these similarities. Without considering the geologic origin and compositions of parent materials, the value of diagnostic criteria can be compromised. 115 REFERENCES BARTLETT, R.J. (1972). Field test for spodic character based on pH-dependent phosphorus adsorption. Soil Science Society of America Proceedings 36, 642-644. BASCOMB, C ,L . (1968). Distribution of pyrophosphate-extractable iron and organic carbon in soils of various groups. Journal of Soil Science 19, 251-268. BIRRELL, K.S. (1964). Some properties of volcanic ash soils. World Soil Resources Reports 14, 74-81. F.A.O., Rome. BLUME,H.P. and SCHWERTMANN, U. (1969). Genetic evaluation of profile distribution of aluminum,, iron and manganese oxides. Soil Science Society of America Proceedings 33, 438-444. BRYDON, J.E. and DAY, J.H. (1970). Use of the Fieldes and Perrott sodium fluoride test to distinguish the B horizons of Podzols in the field. Canadian Journal of Soil Science 50, 35-41. CLARK, J.S., GREEN, A.J. and NICHOL, W.E. (1967). Cation exchange and associated properties of some soils from Vancouver Island, British Columbia. Canadian Journal of Soil Science 47, 187-202. CLARK, J.S., MCKEAGUE, J.A. and NICHOL, W.E. (1966). The use of pH-dependent cation-exchange capacity for characteriz• ing the B horizons of Brunisolic and Podzolic soils. Canadian Journal of Soil Science 46, 161-166. CLOOS, P., HERBILLON, A. and ECHEVERRIA, J. (1968). Allophane- like synthetic silico-aluminas. Phosphate adsorption and availability. Transactions of the 9th International Congress of Soil Science, Adelaide Australia 11, 733-743. C.S.S.C. (1970). The system of soil classification for Canada. Canada Department of Agriculture, Ottawa. C.S.S.C. (1973). Proceedings of the Canada Soil Survey Committee Meetings, Saskatoon. Canada Department of Agriculture, Ottawa. FASSBENDER, H.W. (1969). Phosphorous deficiency and fixation in volcanic ash soils in Central America. In "Panel on volcanic ash soils in Latin America." Section B.4.1, Turrialba, Costa Rica. FRANZMEIER, D.P., HAJEK, B.F. and SIMONSON, C .H. (1965). Use of amorphous material to identify spodic horizons. Soil Science Society of America Proceedings 29, 737-743. 116 GALINDO, G.G., OLGUIN, C. and SCHALSCHA, E .B. (1971). Phosphate- sorption capacity of clay fractions of soils derived from volcanic ash. Geoderma 7, 225-232. HARTER, R.D. (1969). Phosphorus adsorption sites on soils. Soil Science Society of America Proceedings 33, 630-632. HSU, P.H. (1965). Fixation of phosphate by aluminum and iron in acidic soils. Soil Science 99, 398-402. JACKSON, M.L. (1958). Soil chemical analysis. Prentice Hall Inc., Englewood Cliffs, N.J. McKEAGUE, J.A. (1967). An evaluation of 0.1 M pyrophosphate and pyrophosphate dithionite in comparison to oxalate as extractants of the accumulation products in Podzols and some other soils. Canadian Journal of Soil Science 47, 95-99. MCKEAGUE, J.A., BRYDON, J.E. and MILES, N.M. (1971). Differ• entiation of forms of extractable iron and aluminum, in soils. Soil Science Society of America Proceedings 35, 33-38. MEHLICH, A. (1960). Charge characterization of soils. Trans• actions of the 7th International Congress of Soil Science, Madison, Wisconsin 11, 300-311. MEHRA, O.P. and JACKSON, M.L. (1960). Iron oxide removal from soils and clays by a dithionite citrate system buffered with sodium bicarbonate. 7th National Conference on clays and clay minerals, 317-327. PAWLUK, S. (1972). Measurement of crystalline and amorphous iron removal in soils. Canadian Journal of Soil Science 52, 119-123. SCHWERTMANN, U. (1973). Use of oxalate for Fe extraction from soils. Canadian Journal of Soil Science 53, 244-246. SNEDDON, J.I. (1973b). A study of two soils derived from volcanic ash in southwest British Columbia. Ph.D. thesis. University of British Columbia, Vancouver, B.C. SNEDDON, J.I. (1973d). The amorphous and crystalline weather• ing products of two soils developed in volcanic ash in southwest British Columbia. Ph.D. thesis. University of British Columbia, Vancouver, B.C. SNEDDON, J.I., LAVKULICH, L.M. and FARSTAD, L. (1972). The morphology and genesis of some alpine soils in British Columbia, Canada: 11. Physical, chemical and mineralogical determinations and genesis. Soil Science Society of America Proceedings 36, 104-110. 117 SWINDALE, L.D. (1969). Properties of volcanic ash soils. In "Panel on volcanic ash soils in Latin America". Section B.10, Turrialba, Costa Rica. WILLIAMS, E.G., SCOTT, N.M., and MCDONALD, M.J. (1958). Soil properties and phosphate sorption. Journal of the Science of Food and Agriculture 9, 551-559. 11% THE AMORPHOUS AND CRYSTALLINE WEATHERING PRODUCTS OF TWO SOILS DEVELOPED IN VOLCANIC ASH IN SOUTHWEST BRITISH COLUMBIA INTRODUCTION This is the third in a series of studies on two soils derived from Bridge River volcanic ash in southwestern British Columbia. The location and morphology of the soils is des• cribed in an earlier paper (Sneddon, 1973b). The object of this paper is to study the amorphous material and clay mineral characteristics of two soils derived from volcanic ash and examine the methods of extraction and isolation of these materials. The active fraction of soils derived from volcanic ash is associated with inorganic amorphous material (C.S.S.C., 1973; U.S.D.A., 1967, pp. 36 and 89). With increased weather• ing and maturity these soils are also associated with allophane, imogolite and halloysite to varying degrees depending on their pedogenic environment. Inorganic amorphous material is a product of the breakdown of primary minerals and materials. With changing composition and with increasing organisation of amorphous components, secondary minerals form. Allophane represents the least ordered member of a series of secondary minerals and is generally con• sidered to be the principal constituent of the clay fraction of volcanic ash soils (Kitagawa, 1971). 119 The general term allophane was originally used for the amorphous material found in cracks in rocks (Furkert and FieIdes, 1968). Allophanes are now defined as members of a series of naturally occurring minerals which are hydrous aluminum silicates of widely varying chemical composition, characterized by short range order, by the presence of Si - 0 - Al bonds, and by a differential thermal analysis curve displaying a low temperature endotherm and a high temperature exotherm with no intermediate endotherm (van Olphen, 1971). Some workers prefer a more restricted definition such as that proposed by Wada (1967) which defines allophane as an amorphous or nearly amorphous aluminum silicate material with a restricted Si :Al ratio between 1:1 and 1:2. Allophane has been widely studied in soils and in some detail in Japan (Wada, 1967; Kitagawa, 1971), New Zealand (Furkert and FieIdes, 1968; Milestone, 1971) and elsewhere (Kirkham et al., 1966; Raman and Mortland, 1969; Brydon and Shimoda, 1972). These studies come to the same general con• clusions as to the properties and place of allophane in the genesis of the colloidal fraction in soils with only minor differences in interpretations. Imogolite was first identified by Yoshinaga and Aomine (1962) and has been further identified and characterized by a number of authors (Cradwick et al., 1972; Eswaran, 1972; Russell ejb al_., 1969; wada and Yoshinaga, 1968). It has a more ordered structure than allophane, that can be distinguished by x-ray diffraction, electron microscopy and IR spectroscopy. 120 A number of essentially similar weathering sequences of volcanic ash soils, proposed by a number of authors, have been reviewed up to 1969 by Besoain (1969). Since then further genetic sequences have been suggested (Cortes and Franzmeier, 1972; Milestone, 1971; Pettapiece and Pawluk, 1972) though these are again similar to those reviewed, while accepting the inclu• sion of kaolinite in most sequences, as a theoretical logical probability Besoain (1969) questions its actual occurrence, indicating that most clays derived from volcanic ash do not pass through the state of halloysite. Situations where kaolin• ite has been indicated are considered doubtful. Eswaran (1971) in turn suggests that little or no evidence has been observed to suggest the formation of halloysite from imogolite. Indeed Bates (1962) found that halloysite forms first in the alteration of plagioclase in Hawaiian andesites and suggested that it then weathers to allophane and finally to gibbsite. The following illustrates a simplified scheme of the weathering products of volcanic ash which considers the more restricted definition of allophane. Volcanic ash 1 Inorganic amorphous material with a wide range of Si and Al content with some organic complexing and discrete Si and Al possible. 1 Allophane SirAl 1:1 to 1:2 1 Imogolite I Halloys ite 1 Kaolinite 121 MATERIALS AND METHODS The soil materials used in this study were selected from soils at two sites described and sampled by Sneddon (1973b). The composition of the amorphous materials in the clay fraction of these soils was determined following the procedure of Yuan (1969) with minor modifications. The elements Si, Fe, Al, Mn and Mg released by H202 treatment of the fine earth fraction were determined by atomic absorption spectroscopy after each treatment. The soil material from the CB and IIBfb horizons at site 1 was found to be difficult to disperse even after sonification. Not enough clay could be separated from these two materials for the purposes of studying their amorphous characteristics. In addition to the selected soil materials, freshly ground Bridge River pumice and standard (supplied by Wards Natural Science Establishment, Inc., Rochester, N.Y.) montmorillonite (No. 25), kaolinite (No. 5) and halloysite (No. 13) were subjected to a series of chemical treatments used in the separation of allophane and imogolite by Yoshinaga and Aomine (1962a) (see Figure 1). After each treatment the Si, Fe and Al contents of the supernatant solutions were determined by atomic absorption spectroscopy. The procedure was carried out on two sets of materials. The first set was used to determine the contents of acid and alkali dispersable clay (<2/*) and fine clay (<0.2yu). A subsample of clay was taken from the residues of the second set after H2O2 treatment and from the alkali and acid dispersable clays for further study. 122 Soil mater ial <2 mm Separate <2u fraction from a subsample Solut ion determine Si, Fe, Al 2 2 Res idue Separate <2ufraction from a subsample for X-ray and I.R. analysis Solut ion Deferrat ion determine Si, Fe, Al Res idue Solut ion 2% Na2C03 determine Si, Fe, Al Res idue Solut ion Dispersion NaOH (pH 10'.:5 -11) determine Si, Fe, Al D i spersed AK clay Und i spersed D i spers ion <2.0 - 0.2u <0.2y Solut ion HC 1 Al 1ophane Al (pH 3-5- 4.0 ) Dispersed AC clay Und i spersed <2.0 - 2y <0. 2y Imogoli te Figure 1. Flow sheet for separation of allophane and imogalite (adapted from Yoshinaga and Aomine, 1962a). 123 The subsamples of clay were washed three times with a IM NaCHgCOO/NaCl (1/1) solution adjusted to pH5 with acetic acid. This mixture was removed by successive washings of water and methanol (1:1), methanol and acetone (1:1) and acetone. This treatment removed the residual effects of the various chemical treatments. The separated clay fractions were examined by x-ray diffraction, infrared absorption spectroscopy and by electron microscopy. The clays were Mg saturated, Mg saturated and glycolated and K saturated. Orientated glass slides were prepared for x-ray diffraction analyses using Ni filtered Cu Kof radiation. Diffractograms were obtained from K saturated slides at room temperature, 300C. and at 550C. The Mg saturated slides were subjected to x-ray analysis at room temperature and the glycolated slides at room temperature and at 300C. Infrared spectra were obtained by the KBr pelleting technique. Electron micrographs were taken of selected clay sized fractions. Droplets of ultrasonically dispersed sample in water were air dried on a carbon coated microgrid. Palladium was used to obtain shadowcasts of the acid and alkali dispersable fine clay fractions. A total elemental analysis of Bridge River pumice and ash was carried out by semimicrochemical analysis (Jackson, 1958). 124 RESULTS AND DISCUSSION An examination was made of the dissolution effects of H2O2 *n the procedures for the determination of amorphous materials and for the isolation of allophane and imogolite. The results were in close agreement and are meaned and pre• sented in Tables 1 and 4. The dissolution effects are dis• cussed relative to the dissolution effect of peroxide on amorphous materials and on the clay minerals. The amounts of the elements released by H2O2 treatment indicated that treatment effects should not be ignored, as is often the case. In the ash soils the amounts of Si, Al, Fe and Mg released were found to be significantly correlated (1% level) with organic matter content, determined previously on the same samples (Sneddon, 1973b). In the paleosols organic matter was again significantly correlated with Si, Al and Fe but not with Mn and Mg. Soils contain amorphous constituents of inorganic weather• ing products such as Si, Al and Fe alone or in combination or as complexes with organic matter. Some of the free oxides of Fe and Al have a strong pH-dependent capacity to absorb silica that decreases with decreasing pH below pH 9 (McKeague and Cline, 1963b; Jones and Handreck, 1963). The solubilities of Fe and Al increase with a decrease in pH. However, in soils, the solubility of Al and probably Fe, is not directly related to pH. Rather on a more consistent physical chemical basis the relationship is with the solubility product of the hydrox• ide (Clark, 1966). The destruction of organic matter with Table 1. Amount of selected elements released by hydrogen peroxide treatment of the fine earth fraction of the study sites Depth Si Al Fe Mn Mg Hor i zon cm ppm ppm ppm ppm ppm Si te 1 Ah 0 - 7.5 732 4140 3343 163 Bml 7. •5- 12.5 66 1601 119 ND 6 Bm2 12..5 - 23 63 484 21 7 6 Bm4 24 - 29 50 382 13 13 84 CB 29 - 36 125 ND ND ND 4 II Bhfb 36 - k] 406 4502 1267 335 91 II Bfb kx - 46 125 1140 86 253 99 II BCb 46 - 5k 138 8 15 188 323 II CBb 5k -104 125 3 8 521 413 Site 2 Ah 0 - 11 111 356 557 84 23 Cl 1 1 - 25 42 247 64 2 7 C2 25 - 48 52 ND 1 1 7 II Bmb 48 - 61 119 9 4 171 58 II BCb 61 - 86 129 11 5 17 152 II CBb 86+ 104 8 3 19 296 Not detectable Table 2. Composition of the amorphous materials in the clay fraction and ratio of amorphous material in the fine earth fraction to content of silt and clay Ratio of Amorphous Hor izon Component Percent Mole Ratios Mater ial Amorphous Material in clay % silt + clay Si0„ Si0„ A1_0, Fe203 Si02 A1203 2 2 2 3 of fine earth fraction R„0„ A1.0„ Feo0o 2 3 2 3 2 3 Site 1 Ah 66.11 19-04 14.85 4.58 5.90 2.00 48.97 0.62 Bml 45.03 39.17 15-79 2.00 1 .95 3.88 81.10 0.55 Bm2 63.30 30.19 6.51 4.34 3.54 7.25 31 .86 0.33 Bm4 55.92 37.34 6.73 3.22 2.53 8.68 69.52 0.26 CB 0.25 II Bhfb 55.64 24.86 19-50 2.96 3.83 2.00 49.60 0.39 II Bfb 0.44 II BCb 56.36 25.24 18.40 2.87 3.58 2.15 34.42 0.27 II CBb 58.43 20.18 21.39 3.22 4.91 1.48 21 .20 0.31 Site 2 Ah 75.33 21 .99 2.68 7.88 5.81 12.87 57.48 0.32 Cl 79-60 18.42 2.14 9-99 7-33 13.49 58.62 0.42 C2 77-50 20.45 2.05 8.95 6.43 15.81 46.30 0.14 II Bmb 58.95 35.48 5.56 3.68 2.82 9-97 53-52 0.20 II BCb 59.39 35-39 5-21 3.73 2.85 10.64 42.56 0.19 II CBb 58.96 36.58 4.47 3.71 2.73 12.88 49.11 0.20 127 H202 commonly results in a lowering of pH with the greatest charge occurring in soils with the highest organic matter content (Douglas and Fessinger, 1971; Lavkulich and Wiens, 1971). The samples with the most organic matter were treated with correspondingly more H202. The high correlation with organic matter of most of the measured elements may also be related to the pH changes induced by the H202. The values obtained for the elemental contents in the extracting solutions indicated that the elements were not extracted entirely into solution but were also in the colloidal state. Measured concentra• tions were greater than the solubility products of these elements would indicate. Some difficulty was found in the dispersion and separation of clay from the site 1 CB and IIBfb horizons. This was unexpected as the problem had not occurred before with these samples (Sneddon, 1973b). Partial drying or alteration of the samples during storage may account for the change in the dispersion characteristics. The amorphous material content of the ash soils ranged between 31 and 81 percent and between 21 and 53 percent for the paleosols (see Table 2). No well defined relationships were apparent from the distribution of the amorphous materials in the clays. One reason for this could be the different surface area relationships that exist among horizons. Differences are due to the range in fine clay and silt contents and the porous nature of the sand fraction of the ash soils. This is con• firmed to some extent by the values obtained when the ratios of the amorphous material contents of the fine earth fractions divided by the silt and clay contents are considered (see 128 Table 2). In this case at site 1 the amorphous material content decreases with depth in the ash soil. In the paleosol a similar pattern prevails with a slight increase in the IIBfb horizon. At site 2 there is a bulge in the Cl horizon of the ash soil and a decrease in the lowest horizon, C2. The distribution of amorphous material in the paleosol appears to be fairly uniform. Poorly ordered and finely divided clays are considered as being relatively susceptible to dissolution by NaOH while 2:1 clays are considered as relatively stable (Kirkman et al., 1966; Shoji and Masui, 1969). The component percent and mole ratios of the amorphous materials in both the paleosols and in the ash soil at site 2 indicate a uniform relationship throughout each soil but a slightly different relationship among the soils. The difference between soils most probably reflects the different geologic compositions of the parent materials. The amorphous material of the site 2 ash soil for instance exhibits a similar component percent of amorphous material to the Bridge River tephra (see Table 3) if the total Si02, Al203 and Fe203 content of the tephra is expressed on the basis of 100%. This indicates that very little if any translocation of the Si, Al and Fe weathering products has taken place or that ash material in the clay fraction was itself subject to dissolution. It also has been noted previously that among the primary materials of volcanic tephra, volcanic glass is the least stable to chemical weathering (Shoji and Masui, 1969). In the ash soil at site 1 pedologic processes have resulted in translocation and trans• formations of weathering products within the ash solum. A 129 particle size discontinuity above the Bm4 horizon (Sneddon, 1973b) adds to the uneven distribution of materials through the pedon due to its influence on the water movement character• istics of the soil. TABLE 3 Analysis of Bridge River tephra Bridge River Pumice Bridge River Ash % Compos it ion sio2 63.20 65.30 18.10 A1203 18.72 Pe203 2.89 3.36 Ti02 0.47 0.54 CaO 4.32 3.56 MgO 1.15 1.33 K20 1.82 2.09 Na20 5.83 5.21 MnO 0.04 0.05 Total 98.45 99.54 The dissolution effects of the various solutions used in the procedures for the isolation of allophane and imogolite (see Table 4) indicate that a considerable proportion of the amorphous and crystalline clays may be lost in solution. As already discussed the dissolution effects of H202 decreases with depth and organic matter content. Little dissolution of ash material took place but the 2:1 and 1:1 clays exhibited considerable dissolution. This could be significant where minor amounts of clays occur in a soil. Douglas and Fiessinger Table 4. Parts per million of Si, Fe and Al extracted by various reagents used in the isolation of clay fractions of selected soil samples and soil materials H 2% Hor i zon Depth D i th ion i te Na C NaOH, pH1 11 HCl , 2°2 2 °3 PH 3-5 cm Si Fe Al Si Fe Al Si Fe Al Si Fe Al Si Fe Al r\ r\ m r\r ppm or S ite 1 Ah 0-7.5 732 3343 4140 383 4471 1035 1760 5 10 414 8 26 85 2 1 1 Bml 7-5-12.5 66 119 1601 258 2239 973 25 5 385 30 1 61 46 1 3 Bm2 12.5-24 63 21 484 141 1211 565 15 2 353 20 ND* 91 20 1 2 Bm4 24-28 50 13 382 136 464 452 20 5 382 10 ND 60 46 1 3 CB 28-33 125 ND ND 80 322 26 20 2 332 10 ND 65 12 1 4 II Bh'fb 33-38 406 1267 4502 346 10156 4816 42 8 139 63 4 52 79 2 11 II Bfb 38-43 125 86 1140 280 12639 3337 16 3 311 26 3 143 114 7 25 S ite 2 Ah 0-11 111 557 356 262 1872 1329 19 5 374 56 4 66 45 ND ND Cl 11-25 42 64 247 78 342 114 123 1 ND 46 1 9 22 ND ND C2 25-48 52 1 ND 87 258 131 19 3 58 48 ND 19 17 ND ND II Bmb 48-61 119 4 9 189 5957 496 15 2 109 79 9 60 24 ND ND Selected Materials Mazama pumice 35 ND ND 136 1258 45 604 1 ND 111 ND 3 44 1 2 Bridge River pumice ND ND ND 237 1613 907 15 5 403 61 3 76 16 1 4 Montmor i1 Ion i te 6500 140 5000 2600 3100 300 5750 75 1000 1750 75 250 1250 60 100 Kaoli n i te 1000 35 1200 375 425 250 1688 6 1188 438 6 100 313 15 25 Halloys i te 1500 35 400 750 825 775 813 6 1250 625 13 313 438 15 88 U) * ND not detected o 131 Table 5- Percentage of clay (<2y) and fine clay(<0.02u) separated by alkali and acid dispersion Material dispersed Material dispersed in NaOH at pH- 1-0.-5 in -HG-1 -at -pH- 3 .5- Horizon Depth % 2-0.2y % <0.2y X 2-0.2y X <0.2y cm Site 1 Ah 0-7-5 2.46 2.80 0.53 0.02 Bml 7.5-12.5 0.56 0.08 0.20 0.05 Bm2 12.5-23 1.14 0.40 0.48 0.07 Bm4 24-29 0.46 0.07 0.15 0.01 CB 29-36 0.48 0.06 0.62 0.06 II Bhfb 36-41 5.68 4.05 0.44 0.13 II Bfb 41-46 5-01 3.35 0.88 0.32 Site 2 Ah 0-11 1.08 0.55 0.24 0.05 C1 11-25 0.35 0.05 0.13 0.01 C2 25-48 0.36 0.03 0.08 0.01 II Bmb 48-61 2.36 0.16 0.35 0.01 Selected Materials Mazama pumice 1.50 0.10 0.70 0.06 Bridge River pumice 1.14 0.42 0.42 0.07 Montmori1 Ionite 12.40 16.24 2.20 3-60 Kaol inite 46.70 8.80 0.25 0.65 Halloysite 59-90 10.40 2.55 0.75 132 (1971) found that the diffraction line intensity of certain clays was reduced as a result of H2O2 treatment in the presence of organic matter. The dissolution effects of dithionite are particularly effective in the case of Pe though the H2C>2 treatment released more Si and Al in some cases and especially in the case of the standard clays. Some dissolution of the tephra materials took place with Fe being released in the greatest quantity. The remaining 3 dispersing agents, Na2CC<3, NaOH, and HCl, brought considerably less material into solution compared to H2O2 and dithionite though considerable amounts were still released from the standard clays. The tabulated values give an indication of the dissolu• tion capabilities of the solutions taken in sequence. Considerably less amorphous material is isolated by the method used to isolate acid and alkali dispersable clay and fine clay than by the NaOH dissolution technique. More material was dispersed by NaOH in both clay fractions, 2-0.2^ and < 0.2^, than by HCl (see Table 5). The x-ray diffraction patterns indicate that the clay fraction of the volcanic ash soils consists mainly of chlorite and plagioclase feldspar with lesser and infrequent amounts of mica, kaolinite, chlorite integrades, vermiculite, montmoril- lonite and some quartz and possibly cristobalite (see Table 6). The clay fractions of the paleosols have a similar composition to those of the ash soils with the addition of mica at site 2 and montmorillonite and vermiculite at site 1. Site 2 appears to lack any integrade material. Table 6. Clay fraction components estimated3 from X-ray diffractograms Horizon Chlorite Chlor i te Mica Vermiculite Montmori11 onite Kaolinite Quartz Feldspar i ntergrade Site 1 Ah 3 1 3 3 Bml 3 2 3 Bm2 2 2 3 Bm4 3 3 CB 3 3 II Bhfb 3 1 2 1 II Bfb 3 1 2 1 II BCb 2 2 3 2 2 II CBb 3 2 Site 2 3 Ah Cl 2 2 1 C2 2 II Bmb 2 3 II BCb 2 2 2 II CBb 2 a 1 = 0-15^; 2 = 15-30%; 3 = >30%. 134 The two surface horizons of the ash soil at site 1 contain quartz and kaolinite which is believed to be from an aeolian source. This is indicated by the lee slope landscape position of the site (Sneddon, 1973b) with indications of aeolian accumula tions. Neither of these minerals occur in the underlying ash materials. The occurrence of a minor amount of mica in the Ah horizon could be inherited or have an aeolian source. The chlorite integrade material is probably forming at the expense of chlorite which is being weathered in the direction of vermica- lite. The occurrence of montmorillonite in the Bm4 horizon at site 1 does not appear to fit into the logical sequence of weathering indicated by the other horizons or the accompanying minerals in the horizon. It may occur in other horizons in amounts too minor to be detected in the initial diffractograms or has been subject to dissolution in the solutions used to prepare the samples for analysis. Cristobalite may be present as an inherited mineral in the ash horizons at both sites though this could not be confirmed. The occurrence of a peak at the 4.04A position was considered to be a second order plagioclase peak though cristobalite could have been present in a minor amount. Lower order peaks were not evident at 2.48A or 3.15A. The I.R. spectra exhibits a peak at 800cm""1 which is indica• tive of cristobalite and amorphous silica. Similar interpretations were made of the clay fraction of the ash soil at site 2. The decrease in the content of plagio• clase with depth possibly reflects a decrease in weathering intensity affecting the release of plagioclase phenocrysts in the glass. Figure 2. I.R. spectra of amorphous Si and A) and of the clay fraction of ground Bridge River pumice, the site 1 Ah and II Bfb extracted after treatment A, alkali D and acid E dispersion. 136 The dominance of chlorite in the ash soils is attributed to the rapid weathering of biotite hornblende and pyroxene inherited from the parent tephra. The minor and sporadic detection of mica in the ash derived materials suggests that it has a short life span in the soil, once it is exposed to a weathering environment. The clay content of the site 1 paleosol shows some similar• ities to the overlying ash soil. The kaolinite is believed to have been inherited. The montmorillonite could have formed by the rapid weathering of inherited mica or the weathering of vermiculite. Its relative abundance in the IIBCb and IICBb horizons also could be the result of its translocation during the initial development of these horizons. The effects of the various dissolution treatments on the IR absorption spectrographs of the whole clay fraction was to increase the intensity of the absorption bands of the crystal• line materials and reduce the intensity of the bands associated with organic matter and inorganic amorphous material. The intensity of the quartz doublet at 780-800cm-1 increases in the spectra of the IIBfb horizon (see Figure 2) going from sample A to E. Where sample A refers to the clay material sampled after H202 treatment, D refers to alkali dispersable and E acid dispersable clays. Absorption bands in the region of 2900cm""1 and 1400 to 1600cm""1 generally decreased in inten• sity or disappeared with increasing dissolution. The bands in the region of 2900cm""1 were attributed to organic materials, some of those in the 1400 to 1600cm""1 region to humic materials and some in the region of 1600 to 1640cm"1 to inorganic 137 Jgj < Figure 3 A, Imogolite like material isolated frcm the Ah horizon at site 1; B, Single filament of imogolite like material isolated from the II Bmb horizon at site 2 and characteristic of most hr.ogolite like particles found i n other hor i zons. 138 amorphous materials such as allophane. The absorption spectra of the clays supported some of the interpretations of the x-ray analysis eg. the presence of kaolinite was indicated by absorp• tion bands in the region of 3695, 3620 and 915cm""*. The super• position of bands of the different materials present meant that some of the bands could not be resolved without further treat• ments and comparisons of the spectra. The IR spectra of the acid and alkali dispersable fine clays exhibited similar absorption spectra with more diffuse bands in the OH stretch and SiO stretch regions and very little in the SiO bending region at 3000 to 3800, 800 to 1100 and from 800 to 400cm~*, respectively. This reflected the inclusion of crystalline and poorly organised material, the reduction in the primary mineral content and the similarity to the spectra of the total clay fraction. The electron micrographs of the acid dispersable palladium shadowcasted fine clay showed some evidence of material with the morphological characteristics of imogolite (see Figure 3,A). This material was not detected without shadowcasting and was most readily detected in the acid dispersed fine clay from the Ah horizon at site 1. The relative abundance of this material in the other horizons could not be judged as a large number of fields had to be observed with often only a single filament being detected at a time (see Figure 3,B). This material could not be positively identified as imogolite as it was not indicated as being present by either x-ray or I.R. techniques. Formation of imogolite could have taken place in isolated capillaries of the ash and pumice particles. Leaching would 139 Figure h. Halloysite like particles observed in the electronmicrograph of the acid dispersed fine clay fraction of the site 2 II Bmb horizon. 140 ure 5. A, Gel like material associated with acid dispersed halloysl B, Gel like material associated with acid dispersed II Bhfb material from s i te 1. 141 account for the occurrence of particles in the paleosols. Wada (1967) proposed a fibrous shape for allophane, based on chemical analysis and I.R. data, which this material could represent. The material also could have formed in solution after separation. The dissolution effects measured during the coarse of the procedure for the isolation of imogolite suggests that it is unlikely that single filament particles as observed in the electron micrographs could survive. However the material could have survived in an amorphous gel and have been released during the treatment for the isolation of the alkali soluble fraction. Halloysite-like particles were present in all horizons (see Figure 4) in varying amounts. Also, they were more evident in the acid than in the alkali dispersable fine clay fractions. The amount of halloysite that was evident was minimal and was not indicated as being present by x-ray or I.R. techniques. Some of the clays extracted after acid dispersion exhibited etched surfaces. A gel-like material was observed in association with the acid dispersed halloysite particles, of the standard halloysite clay samples, (see Figure 5,A) and the acid dispersed IIBhfb material from site 1 (see Figure 5,B). Either the alkali dispersion treatment did not fully remove all of the allophane material or the acid dispersion treatment resulted in further dissolution and gel formation. Allophane or allophane-like particles did not dominate the alkali dispersable fine clay fraction. Aggregates of rounded grains characteristic of some forms of allophane (Bates, 1971) were observed in some of the micrographs of the alkali dispersed 142 clay. In general, the differences between the alkali and acid dispersable clays was not marked. Treatments used to remove organic matter and sesquioxides and in dispersion also remove portions of the clay mineral and amorphous material content. In the measurement of the amorphous material content of soils chemical dissolution gives a measure of the material most susceptible to dissolution which includes amorphous material, the finer fractions, micelle edges and some of the surfaces of clay minerals. X-ray diffraction analysis proved to be the most useful analytical technique for the identification of the minerals in the clay sized fraction. Infrared analysis provided a positive indication of the presence of kaolinite which is sometimes difficult to identify by x-ray analysis in the presence of chlorite. Electron microscopy provided little information to confirm the findings by x-ray and I.R. analysis. This technique did indicate the presence of halloysite and imogolite-like minerals present in such minor amounts that they were not detected by x-ray or I.R. analysis. The amorphous material content of the soils ranges from 21 - 81 percent of the clay fraction. The clay mineral content consists mainly of chlorite and plagioclase feldspar with lesser amounts of mica, kaolinite, vermiculite, montmorillonite, chlorite integrade, halloysite and imogolite-like minerals and some quartz and possibly Cristobalite. A similar content of clay minerals was found in soils formed on Mazama pumice by Chichester et al., (1969) who indicated that alumination of 2:1 layer silicates results in 143 the formation of chlorite intergrades, and extends to the formation of pedogenic chlorite. Even though there may have been some dissolution of primary materials, it is believed that the high Si:Al ratios would not be conducive to the alumination of 2:1 layer silicates in the case of the soils in this study. The relative youth of the ash soils in this study (about 2,440 years before present) and limited soil development at site 2 suggest that alumination of 2:1 layer silicates would involve a much longer process than has taken place in these soils. The unique micro-environments occurring may provide a range of suitable conditions for the formation of clay minerals that do not reflect the overall weathering environ• ment. CONCLUSIONS From the data collected in this study the following con• clusions are drawn. All of the solutions used in the treatment of the soils for the removal of organic matter and sesquioxides and for dispersion resulted in some dissolution of soil material. Treatment for the removal of amorphous material results in the dissolution of amorphous and primary materials. With the majority of the Si to Al ratios being greater than 2 discrete amorphous silica is indicated as being present in some if not all horizons. The affinity of Al for Si in solution (Mitchell e_t al., 1964) means that most of the Al released by weathering combines with Si to form amorphous aluminosilicates. As the Si to Al ratio of the amorphous material in these soils approaches 1:2 the formation of allo• phane (Wada, 1967) and imogolite will take place. The minor amounts of imogolite detected formed in isolated capillary channels where conditions suitable for the formation of this material occurred. The presence of occasional lathes of halloysite are considered to be a product of plagioclase weathering. The chlorite, the dominant clay mineral in the ash soils, is derived from the weathering of the biotite, pyroxene and horneblende (Fields and Weatherhead, 1966; Kawasaki and Aomine, 1966) present as phenocrysts in the parent tephra. 145 REFERENCES BATES, T.F. (1962). Halloysite and gibbsite formation in Hawaii. Clays and Clay Minerals. Proceedings National Conference Clays and Clay Minerals (1960) 9, 315-328. BATES, T.F. (1971). The kaolin minerals. In "Electron- optical investigation of clays." (J.A. Gard, Ed.), pp. 109-157. Mineralogical Society, London. BESOAIN, E. (1969). Clay mineralogy of volcanic ash soils. In "Panel on volcanic ash soils in Latin America." Section B.l.l. Turrialba, Costa Rica. BRYDON, J.E. and SHIMODA, S. (1972). Allophane and other amorphous constituents in a podzol from Nova Scotia. Canadian Journal of Soil Science 52, 465-475. CHICHESTER, F.W., YOUNGBERG, C.T. and HARWARD, M.E. (1972). Clay mineralogy of soils formed on Mazama pumice. Soil Science Society of America Proceedings 33, 115-120. CLARK. J.S. (1966). The relation between pH and soluble and exchangeable Al in some acid soils. Canadian Journal of Soil Science 46, 94-96. CORTES, A. and FRANZMEIER, D .P. (1972). Weathering of primary minerals in volcanic-ash derived soils of the central Cordillera of Columbia. Geoderma 8, 165-176. CRADWICK, P.D.G., FARMER, V.C., RUSSELL, J.D., MASSON, C.R., WADA, K. and YOSHINAGA, N. (1972). Imogolite, a hydrated aluminum silicate of tubular structure. Nature Physical Science 240, 187-189. C.S.S.C. (1972). Proceedings of the Canada Soil Survey Committee Meetings, Saskatoon. Canada Department of Agr iculture, Ottawa. DOUGLAS, L.A. and FIESSINGER, F. (1971). Degradation of clay minerals by H202 treatments to oxidize organic matter. Clays and Clay Minerals 19, 67-68. ESWARAN, H. (1972). Morphology of allophane imogolite and halloysite. Clay Minerals 9, 281-285. FIELDES, M. and WEATHERHEAD, A.V. (1966). Mineralogy of sand fractions of New Zealand soils. New Zealand Journal of Science 9, 1006-1021. FURKERT, R.J. and FIELDES, M. Allophane in New Zealand soils. International Congress of Soil Science Transactions 9th (Adelaide, Australia) III, 133-141. 146 JACKSON, M.L. (1958). Soil chemical analysis. Prentice Hall Inc., Englewood Cliffs, N.J. JONES, L.H.P. and HANDRECK, K.A. (1963). Effects of iron and aluminum oxides on silica in solution in soils. Nature 198, 852-853. KAWASAKI, H. and AOMINE, S. (1966). So called 14A clay minerals in some Ando soils. Soil Science and plant nutrition 12, 18-24. KIRKMAN, J.H., MITCHELL, B JD. and MACKENZIE, R.C. (1966). Distribution in some Scottish soils of an inorganic gel system related to "allophane". Transactions of the Royal Society of Edinburgh LXVT, 393-418. KITAGAWA, Y. (1971). The unit particle of allophane. American Mineralogist 56, 465-475. LAVKULICH, L.M. and WIENS, J.H. (1971). Hydrogen peroxide- organic matter-pH interactions. Soil Science Society of America Proceedings 35, 1971. MCKEAGUE, J.A. and CLINE, M.G. (1963). Silica in soil solutions. II. The adsorption of monosilicic acid by soil and by other substances. Canadian Journal of Soil Science 43, 83-96. MILESTONE, N.B. (1971). Allophane - its structure and possible uses. Chemistry in New Zealand 35, 191-197. MITCHELL, B.D., FARMER, V.C. and McHARDY, W.J. (1964). Amor• phous inorganic materials in soils. Advances in Agronomy 16, 327-383. PETTAPIECE, W.W. and PAWLUK, S. (1972). Clay mineralogy of soils developed partially from volcanic ash. Soil Science Society of America Proceedings 36, 515-519. RAMAN, K.V. and MORTLAND, M.M. (1969). Amorphous materials in a spodosol: some mineralogical and chemical properties. Geoderma 3, 37-43. RUSSELL, J.D., McHARDY, W.J. and FRASER, A.R. (1969). Imogolite: a unique aluminosilicate. Clay Minerals 8, 87-99. SHOJI, S. and MASUI, J. (1969). Amorphous clay minerals of recent volcanic ash soils in Hokkaido (I) Soil Science and Plant Nutrition 15, 161-168. SNEDDON, J.I. (1973). A study of two soils derived from volcanic ash in southwest British Columbia. Ph.D. thesis. University of British Columbia, Vancouver, B.C. 147 SOIL SURVEY STAFF (1967). Soil classification, supplement to 7th approximation. Soil Conservation Service and U.S.D.A. Washington, D.C. VAN OLPHEN, H. (1971). Amorphous clay minerals. Science 171, 91-92. WADA, K. (1967). A structural scheme of soil allophane. American Mineralogist 52, 690-708. WADA, K. and YOSHINAGA, N. (1968). "The structure of "Imogolite." American Mineralogist 54, 50-71. YOSHINAGA, N. and AOMINE, S. (1962). Allophane in some Ando soils. Soil Science and Plant Nutrition 8, 6-13. YUAN, T.L. (1968). Composition of amorphous materials in the clay fraction of some entisols, inceptisols and spodosols. Soil Science 107, 242-248. 148 SUMMARY Volcanic ash is widely distributed in western Canada. The amounts present in soils vary with distance from the source and position on the landscape. Studies on two soils derived from Bridge River volcanic ash indicate that in these youthful soils the physical properties are inherited from the parent material. The colloidal and chemical properties are initially imparted by organic matter with some influence from the weathering products of ash and especially aluminum. With increasing age and in more intensive weathering environments physical properties would develop that are more pedogenic in origin and chemical properties would develop that to a greater extent are imparted by the weather• ing products of the ash. In evaluating the methods used to identify spodic horizons pyrophosphate, pyrophosphate dithionite, citrate dithionite extractions, phosphate sorption capacity and pH- dependent cation exchange capacity determinations all high• lighted podzolic B horizons and were not affected by the presence of ash. Acid ammonium oxalate and pH in NaF did appear to be affected. Extractions of the clay fractions of these soils determined that they consisted of from 31 to 81 percent of amorphous material. Some crystalline and primary amorphous material also contributed to these values. The Si:Al ratios were greater than 2 indicating the presence of free silica. As the Si:Al values approach 2 the formation of allophane and 149 imogolite will take place. Very minor amounts of imogolite- like material and halloysite were detected. The former most likely formed in isolated capillaries where favourable condi• tions developed. The latter is considered to be a weathering product of plagioclase.. Chlorite is the dominant clay mineral in the ash soils and is believed to be a weathering product of the primary biotite, horneblende and pyroxene present as phenocrysts in the ash materials. Shallow additions of ash will influence soils to varying degrees depending on the bioclimatic environment and depth of material added.