i'i crc. orphol ogy' a, ] GC~n C ic Inter protal lous
or' Selcc.ced Colunbian Andosols
FRANK GILBERT CALHOUN, JR.
A DISSERTATION PRESENTED TO THE 'GRRAOIATE COUNCIL OF
THE UNIVERSI Y OF FLORiOA !;I PARTIAL.
FULFILLMENT OF I HE RF'QJIlRE;TE:T'S P OR HilE OLGREE OF
OJCTOR OF PHILOSOPHY
jUN 'ERSIT'' 'F FLORIDA
AC, I CL.iEUTS
t .au or wi ,:s to exprc-s his sinar p: ,prieci ion to 1r.
Victor W. Carlisle for his unid!.nce, crncouragci-ent, and a:sistancP.
,'urin] th' progress of this i vesti ati on. Appreciations are extended
to Drs. R Caldwill . L, Popenoe, F. l. Blanchard, and A. F. Lugo
for their interest and partici pation on the SnLuper,'isoy/ Cor,.li ttec and
r-view of this manuscript.
Supreme grati ude is expressed to Dr. Carlos Luna For hi hospi-
Ality and guidance during the Coloimian portion of this research.
i'ho author is grateful to !n nioo Agronoini Vic or. _Vega and Dr.
r niicisco Si lva for labor Lory fci;i tie-s t.hey ,,:ost kinil' y miade Freely
avail blie. Appreciation is expresoJ to Insi ti to Georjrofi co ":'Lgustin
Ccoazzi" for travel arr, ngn'nts, !Lot'i lotis tic and financial within
'olorbia Gratitude is exinded to Sr. L.,-o ;nid s taj a foir 1 ils assis-
IIance in mi cromorpho o ical a nai /es d ur i td'e el hr'1onC Ic Y tage of
this inves tigation. Sincere tanlk na nre ex.pre,'d the laboratory
tcchnicians in the "Laboroorio Je Sucos" n fo hil irig LoIdI!Ct misny
of thS routine chemical and physical analyses. Th'e au ,or i so cannot
fully express his dcup appreciation to th"e gi'o-iomi.'ts ao oth r
Colombian citizens for the many kinmrnesses i-,' e" -'.rd-' .o hiim.
The author is indeb -eJ o Dr. C. r. '.no for ajrcring the i'OEA
Ti i!e 1V [Fail .snlip which tacili at, this stuiy. Gr 'ci .u e is -l xten
to the. Ce.itr for Ti'o iOcai /,ric':i itui for pro i:;i, g :d. di ioi'i finan-
rcal support for th;s work both ;n Colo,,bia ard at the University of
i1o c- a.
Thanks are c 'd to Dr. 0, H. iubbell for access to p.oto-
graphic equipij' a i !1: oratory space during micron orlphol :icl i;n
-,etigations. Appreciation is expressed to Dr. L. I. rZel ny fcr
operational assistance in X-ray diffraction techniques :rd Icli~pl
consul tatli. pertaining to this study.
A special thanks to Sr. 'Juliali Velez for occasional Spanish trans-
The author wishes to express special commiendar ion to Mrs. Lillian
S. Ingenlath for excellent typing and proof'ng of this dissertation.
Above all, the author takes this opportunity to express deepest
gratitude to his wife, Nancy, whose unyielding encourajeisent, labcr,
and understanding contributed beyond measure to the successful coaple-
tion of this dissertation.
TASLE OF COHTE.iNTS
LIST OF TABLES . . . .
LIST OF FIGURES . . .
ABSTPAC1 . . . .
INTRODUCTION . . . . . . .
LITERATURE REVIEW . . . .
Andosols . . .
Definition . . . . .
Occurrence . . . . .
Morphology . . . . .
Physical . . . . .
Chemical . . .
Mineralogy . . . . .
Microfabric . .
Al lophane . . . . . . .
Introduction . . . . .
Structure and Compesi Lion
X-Ray Diffracltio Data ..
Differential Thermal Analysis
Infrared Spectrosco .
Dehydration and .':ehydialionr
Surface Area . . . . .
Optical Prope-. ties ......
Ion Exchange and Sorption
Fedocrnetic a iherng .
t i,>ti-,. ..... ..........
MATERi .i.3 AND IHETHMIs ....... .
Si .c P3 roce: n . . . .
fielc Proce,-' r.s . . . .. .
Physical I -thods .... .. .. . . . 26
Fa S-i;2 Size Dist ibut n . . . . . 26
Bulk Cc i t . . . . . . . . . 27
F; fteen-Atmosphare Water Cciat-.t . . . . .. 27
Chem; ca Metods . . . . . . . . . 27
pH Determin-tion . . . . . . . . . 27
Cation Exchange Capacity . . . . . . . 27
Exchangeable Calciurn and !agnesium . . 27
Exchanjgeable Potassium . . . ... . 27
Exch r.,geable Sodium . . . . . . . . 28
Organic Carbon . . . . . . . . 23
Exchan enable Alumiu . . . . . . 28
Free iron Oxides . . . . . . . . 28
Mineralogical Methods . . . . . . . . 28
Dispersion an" Fri-ciotionon of Clay . . . . 28
X-Ray Diffractiojn . . . . . . . .. . 30
DSfFerential Thermal Analysis . . . .... .. 32
Infrared Spectro-,etry Analysis . . . . . . 33
Sodium Fluoride Test for Allophane . . ... 34
Sand Miieralogy . . . . . . .. . . 34
Mi cron;iorphclogi Thin Seccicn Techniques . . . . 35
in regnat l or ........ . . . . . . 35
Preparation oF Thin Sections . . . . .. .. 35
Apaiysis i . . . . . . . . . . 36
DFS.RIPTIOi; COF HASRli STUCY AREA . . . . . .. 37
Location . . . . . . . 37
Physiography . . . . . 37
Bej,-otk and Surfi;ia1 Geology . . . . . . . 39
Cli ;H ate. . . . . . . . . . . . . .
Plant Eco!ogy . .. . . . . . . . . 45
Dry Sub-raopical Forest . . . ... ... 45
Dry Lowa-er Mlontae crest . . ......... 4
mi Lw r ontane ores . . . . .
:umlid icpta;a Forest . . . . . . . . 17
Sub-Alpin' Grassl a ds . . . . . . . 49
uLI A D CIS i ON . . . 51
V-th :y . 'r ; . . ............. 51
O lnic M li ter Uxi4.tion . . .. . . . 51
Oi'o;rsion of Ando Clays . . . . . . 51
Morphclogy . .. ............ . . . 56
Chemical Properties . . . . . 60
Soil Reaction . . . . . . . 60
Organic rbon .. ... . . . ... . 65
Exchlaiige-JJ cases ................. 65
Exchani., aJb e Aluminum . . . .. .. .. 66
Cation cxchSnge Capacity . . . . 67
Free lion Oxides . . . . . . . . . 67
Sodium Fi oiride Test or Al lophane . . ... 67
Genetic Ilterr-'latiorships of Chemical
Properties .. .. .. .. .. ...... 67
Physical Proper'ies ...... ......... .. . 69
Sand Hilin ralogy . . . . . .. . . . . 72
Light Minerals . . . . . . . . . . 72
iHea'v7i !- nerals .. . . . . . . . . . 777
Genetic Relations of Sand liinera!
Distrihut ons ...... . . . . . 78
Clay Mlineralogy . ... ... .............. 79
X-Ray D fraction . . . . . . . .. 79
S rrar i P'nalysis ... . . . ... . . 102
Differ -en ial Therma Analysis. . . . .. 117
Mi cro.ao' pholo .y . . . . . . . . . . 119
Pescri ti vc Features . . . .... .. . . 124
Cen-Lic lntarpreta tions . . . . . .. i 28
SUMMARY .. . . ... .. . . . . ..... . 33
CONCLUS ICGrS . . .......... . . . ... 139
APFENDI X ................... . ....... 143
Lli 'l ATURE CITED .. . . . . . 190
i OGRAPH CA. SKETCH . . . . . . 197
I IST Oi Ai bLES
.hbl e Page
0 Cli .I: rc ationshi p in
De a .,. ., Colo.A i . . . . . I
2. Fe, Sij, AI a 1ol.nis in "xLlact:, after
treal.r,;it of certain Andosol horizons by
iN'OCI o, H . . . . . . 52
2. EFF .ct of pr tiadtii:nt aIid dispersing
ac nt on particic size distr ib tion . . 55
i. Chti-nical prop ,r ti- s of selec.eJ Coloi bian
soils . . . . . 6
5. Ph',i;c l r -'pe '1 ies of selected Colonbian
oil s . . . . .. . . 70
G. Sad (50-500 ,; f' ,.'tion) miniralogy oF
seei ctcd Colo:rbian s.i ls . . . . . . 773
7. Cry. all ine *,ii;Cer: l recognized froi m
X-ray d;ffrct on itIcerns of the f 'n
cliy (<0.2 ,) a .oirse clay (0,2 2 .)
fractions oi sel',:itd Colombian soils . . . 92
8, 1ecta i;d Field description of s-eleced
Colom.ibian soils . . . . . . . . .. 143
9. The d/n spacing of crystal ne minerals
re olii zed firoi X-ray dii fraction pfatL rns
of 'th fine clay (<0,2 p) fraction of
s,.ccted Colombian soils . .......... 15/
!0. Tl'h d/ri s:pacing of rristalline minerals rec-
oni.--ed fron X-ray i fraction patterns oi
ith; oarce clay (0.2-2 p) fraction of selected
Colcrbian ooils . . . . . .. ... i0i
I1. Kicr c /ph-ology of selected Colombian
Ando ol s . . . . . . . . . . 166
LIST OF FI;OGES
1. Departameinto of Nari o located in south-
western Colombia . . .............. 25
2. Colombia, South Am-erica, lshcrwing location
of the Departamento of iari;o ...... ... 38
3. Cross-section of Nilr o, Colombiastudy area
showing locations of profiles 1-6 relative
to Volcano Galeras ...... ... ..... 41
4. Pumice beds 1 km north of Ecuadorian border . . 42
5. Typical vegetation of sub-alpine grassland
near profile 6 .................. 50
6. Color photographs of profiles I-4 rcpresent-
ing altitudinal sequence of 2,00- 2,730 a . 58
7. Color photographs of profiles 5 and 6 rep-
reo-Ceinci attitudinal sequence of 3,120 -
3,510 m and ancillary profiles 8 and 9 at
3,020 and 3,060 m ........... ... 59
B. X-ray diffraction patterns of Ig-satura Led
air dry, K-saturatcd 100C, end K-saturated
500C treated coarse clay of horizon. A
pro file 7 demonstrating identification of
netaalloysi te, hydrated hilloysite, il i e,
and vermiculite by changc.f in d-spccings . 80
9. X-ray diffraction patterns of rg-saLtrated
coarse clay (0.2 2 ),) and fine clay
( <0.2 u) Fractions of profile I ......... 82
10. X-ray I ffraci on patterns of Hig-saturaled'
coarse clay (0.2 2 pi) and fine clay
(<0.2 p) fractions of profile 2 .. . . ... 83
11. X-ray diffraction patterns of ig-saturated
coarse clay (0.2 2 u) and fine clay
(<0.2 ;j) fractions of profile 3 ............. 4
2. Y ri iIr .io n frns alii, d
c .' c!y (0),2 ? :) anOi tini clay
(C O. I) 1r.r ': ,r 's oF pro file .
i X- y i frac ti i r s of I- sa Lurated
cc i c cli. (0.2 2 ji) and Iine clay
(< 0. j ) i' ctiors of profit le 5 .
14. X-r i fr iio pc.ati ternsi o r l-satur ted
coarai clay (0,2 2 j) and Fine clay
(< 0.2 i ) fractions of profit le 6 . . .
16. X-ray di ffraction patterns of Hg-saturated
coarse clay (0.2 2p) and fine clay
(< 0.2 ji) fractions of profile 7 . . . .
16. X-ray diffraction patterns of Mgl-saturated
coarse clay (0.2 2 u) and fine clay
(< 0.2 tj) fractions of profile 8 . . . . .
17. X-ray diffraction patterns of Mg-saturaLed
coarle clay (0.2 2 ii) and fine clay
(< 0.2 j) fractions of profile 9 . . . .
18. X-ray diffraction patterns of Mg-saturated
coarse clay (0.2 2;1) and fine clay
(< 0.2 j) fractions of profile 10 . . .
19. Infrared spectra of coarse clay (0.2 2P)
nrd fine clay (<0,2 )) Fractions of
profit 1 . . . . . . . . .
20. Infrared spectra of coarse clay (0.2 2 p)
Ind fire clay (<0.2 F) fractions of
profit . . . . . . . . .
21. Infrac d spectra of coarse clay (0.2 2 p)
and fine clay (< 0.2 1) fractions of
profile 3 . . . .
22. Irfrared spectra of coarse clay (0.2 2 )1)
and fine clay (<0.2 .i) fractions of
profile 4 . . . . .
23. Infrared spectra of coarse clay (0.2 2 i)
and fine clay (< 0.2 ) fractions of
profile 5 . . . . .
24. Infrared spectra of coarse clay (0.2 2 1)
and fine clay (< 0.2 y) fractions of
pro ile 6 . . . .
25. Infrared spectra of coarse clay (0.2 2 i)
and fine clay ( <0.2 y) fractions of
profile 7 .. ......... ......... 10)
26. Infrared spectra of coarse clay (0.2 2 j)
and fi-e clay (< 0.2 y) fractions of
profile S . . . . . .... . .. .. 110
27. Infrared spectra of coarse clay (0.2 2 u)
and fine clay (< 0.2 j) fractions of
profile 9 .......... ........ ... III
28. Infrared spectra of coarse clay (0.2 2 )
and fine clay (< 0.2 p) fractions of
profile I0 ......... ....... 112
29. Infrared spectra of coarse clay (0.2 2 p)
and fine clay (<0.2 i) fractions of ki, 119
buried argillic horizon; Ward's halloysite
No. 12; and KBr blank ............... 113
30. Differential Lhermal patterns of coarse clay
(0.2 2 Ji) fraction of selected horizons
from profiles I and 10 . . . . . . . 118
31. Photomicrograph of All horizon, profile 3
showing tio fecal pellets set against matrix
of interconnected ortho-craze planes end
orthovughs . . . . ... .. ..... 120
32. Photomicrograph of All horizon, profile 3
showing organan on andesite lithorelict
and subrounded blocky secondary structural
unit set against matrix of interconnected
orthlovughs ........ ......... . ..... 120
33. Photomicrograph of All horizon,profile 3
showing isotic plastic fabric . . . . ... 121
34. Pihoomicrograph of A12 horizon, profile 3
showing feldspar grain wii th weathering
fractures perpendicular to twins . . . 121
35. Fhotcmicrograph of [BJ horizon, profit le 3
showing weakly silasepic and undulic
plastic fabric ............ ...... 122
36. Photomlicrograph of [B] horizon, profile 3
showing hornblende grain with thin,
siliceous isotropic border . . . . . .. 1. 22
37. icro h *f 'i( h ri; i lI 3
i 1 e io Ii (h tit c)
noulo aIind *v, r a mial lor on.. . . . . . 123
38. Phot"ic i-ir ,h of C .horizon, przfilo 3
sho-ing h;i nb g rain wi h t'in,
iiscontinLcii s si i!.n (h'I atan) set
':; i!st i:m trix or inri rcorncted ortCovlJghs . . 123
aernac, o Oi)ss a ition PrsKn-:nd to the
Grad .te Coul :i ci f die Univ-rsity of Flurid: in partial Fu l il e.t
Sthe -,ire 'as for t' gree of 1caor of Phiilso'phy
Mi' CR;CI PP!OLOGY IlND CE:'-FIC IN; EP AlTATI ONS
OF SELICTE; CO.L'o:"IA:I Aid;OSOLS
Frank Gilbert Calhoui, Jr.
Chairman: Dr. Victor WI Carlisle
Major Departrnet: Soil Science
Ten soi! profiles from t're Adean highlands of Departimeno 'ariarno,
Colombia, were investigated by use of chemical, physical, mireralogical,
and micromorpholog9ical techniques in order to elucidate pedocenetlic
processes in soals derived from andesitic volcanic ash anId similarr
parent materials. Six Andosol profiles were selected iin an iltitudinal
sequence from 2,000 m to 3,510 m as representative of maxir'.,; ranog of
weathering severity experienced by aeolian p;roc'lastic :.aterlais ia the
altipliro cf 'i-in'Ro. Four additional soil profiles, 4ev lopirg in
pa:-ent materials with varying degrees of ash iinfl-ence, provided si.pple-
mentary pcdoga'r t'c ;nforn!ation. All of tHe-soils ,.;e re infienced by
annual rainfai? range of 500-2, 00 nn and an annual isothermal tei-:per-
ature range of 6C to !SC ..hih was closely relaLd to li tu.de.
The folio'iljig parameters jwer dter, si ned on :.el ected horizons oi:
each soil: (a) particle size distribution, (b) buik density, (c) fifteen
atmosphere wa ter 'on-tet, (d) pH in water anJ t K;CI. (e) exchi;rqgeah!e
cautions, (f) cation exchange capacity, (g) organic carbon, (h) free iron
oxides, (i) X-ra, diiffraction of fine clay (< 0.2:') and coarse clay
(0.2 2p), (j) infrared analysis of Fine clay and coarse clay, (k) NaF
test for .'lop 'ah cid (!) liih anJi heavy nine' 'l contents "f the sand
,.0 I,0 p ) fr ion', Ili, action, pr apre'I f i, ,1 'h.c EoJ
*ori s of A o- .I p 'fils 1- (2,z 0t 3,510 ;) < d -I cri' cd in
Th 'O'. :.,ntioned an lys,; of Anrkl'ol p o fi 1 -6 r 11e ld the
I i,1 trI S itI inc sin l, v I t io : (I) i cre Ie 5 ir 5c11T1n-e--
'I i K ,iJ Ai; or A a ic carbon; olcanic glass, 1py'O xnes, alrd <,ndesi Lt
Ii ihorl icts in the j0 500 p said fraction; al lophane ni <2 )1 clay
I'rct ion; id isotropi sm of plasiic fabrics in subsurface horizons;
(2) decraasns in FH values; exchdii;nable Ca and Na; free i ron oxides;
quartz, feldspar arl; hornblende in 50 500 p sand fraction; hydrated
hal oysite in the < 2 ) clay fraction; sesquioxidic nodules; ondJ bire-
fri (eiince of plastic fabrics in subsurface horizons.
Vary ng amounts of hydrated hal loys i te, niLahs loysi te, vermicul i ic,
cristoba i Le, gibbsi te, feldspar, and quartz were identi filed by infrared
and X-ray analyses of the coarse clay fraction of Andosol profiles 1--6.
Hydrated hal loysi 'e, nsta'il1 losi te, and possibly allophane A ware
identified in the fine clay fraction.
Andosol surface horizons generally had isotic plasnmic fabrics while
subsurface ho i zons exhibited :wekly unduli c and silasepic pl5sm;c
fabrics which were replaced by isotic plasmic fabrics at higher eleva-
tions. The turri "Andic" vwas proposed as a rodifier for this sequence
of obhrlc types.
A clay mi neral wea hearing sequence or a llophane -- metaha loysi te--)
hydra.ld halloysite was postulated. The maturation of this sequence
increased with profi le depth and wi Lh incre-sii;r a!ti tude. CoIrse clay
varmiculi te was hypothersi ed as be;og tr'Icsi ent sr insui;-r cient time has
elapsed for it's tran forniation Lo other 2:1 phyllosi icaces. it was
Further postulated that vermicul i te pedogenesis occurred rather rapidly/
with some modification from a primary mineral source.
I IRONIC i I ON
Op:or iuni ties h;,.e been al i o r're ora genetic i nv l ig3 tions
in the tropics invol ving soils deri ',J froli na teria ls in an initial
stoie of eri'athering. Research in temperate regions such as New Zealaid
and Japan has disclosed that unique weather ln products occurs during
Lte early stages or primary mineral cdgradation in ?/yroclastic materials.
-3ils dIrivd from such coniniinuted acol in pyroclastic rat, rials (us'sl ly
.'desicic) have been referred to as Andosols. Andosols present very
real mngndgernt call enges due to their aberrant ph;'sical, chemi cal,
-id mi n1ralogical property is. These aberrations are in large pert due
LO their prcence of a lophone w-;hich is a primitive Veqthering prod rt of
There is reason to believe that the genesis of Lropical Andosols
is to some degree thermal dependent. Wright (1961+) noted a "thermal
progression" in r:orphology of low latitude Andosols in Souch America.
There twas ev'ey reason to assume that morphological changes were related
to chemical and r;,ineralonicai di fferences; however, laboratory data w ere
unavailable for substantiion of this potential rsiationship. This
investigation provides such analytical data. it also may be considered
as an addiLion to the general reservoir of kno'.lcedge irgarding the nature
and properties of tropical soils.
Colombia is ore io the worlds' largest coffee exporters. Thiis C op
is grown primarily ard most efficiently on volcanic ash soils of the
highlands. Additionally these soils hold an important role in small
grain and .esetable production fo.- local c, su*.ption. The populace of
Colo-bia is concentrated in the Andcan highlands. iL's eco,',> is
still primarily agrarian ard population expansion i ll continue to
apply considerable pressure on soil resources, especially the com-
paratively fertile Andosols.
A dire need evolves, then, for an accurate inventory and character-
ization of Aniosols, especially in the tropics ..here they most cormonly
occur. Genetic interpretation of these data can add to understanding
of Andosols with concomitant implications to their efficient management.
It would behoove the temperate climate oriented pedologists to partici-
pate in and contribute to these programs in order to broaden their scope
and understanding of soils derived front a wide spectrum of parent
materials. Selection of study sites in close proximity to areas of
historical volcanism would facilitate pedological investigation of
soi s dominated by easily wedatherable primary minerals. With this in
mind,arrangements ;eare mad vith the Insti uto Geografico "Agustin
Codazzi" in Bogota, Colo;mbia, to participate in their program of char-
acterizing and classic ying the Andosols of Colombia.
The intent and objective of the study presented herein was to
elucidate pedogenetic processes occurring in selected Colombian Andosols.
This .qas expedi ted by use of chemical, physical, mineralogical, and
heretofore seldom sedri micromorpholojical paramete-s.
L I Fi RAr u ;: REV I
-Ifini ti o
During sun ,ary and Lcchnical discussions of a "Meeeting on Lhe
Cliasification and Correlation of Soils From Volcanic Ash" held in
Tokyo, Japan ("noyir.ous, 19c5), the following dcini tion was proposed
for Andosols: "Mincral coi Is in which the active fraction is dominated
by a.:or'phous aeriall (rin;mum about 50%). These so Is hlave a hiyh
-orptivc capacity, 3 relatively thick friable dark "A" hori Zon, are
high in organic mi:tei r, have a low bulk density aid a ioi' stickiness.
They :3y have a (F) horizon and no' show sig.iificant clay r.oven:er.t.
These soils occur under humid and sub-hu mid conditions."
With the advent of a new so;l classification system in the Uni ted
States (U. S. Soil Survey Staff, 1970), an important si:border referred
to as ''Andcpt'" was developed which, according to Fiach (!969), en-
compassed ,any of Lhe soils that had beni called And'osois. Andepts
are described ai "i'ore or less freely drained inceptisois that have
Iow blk dr-sity and apprecciabl 1s.ounts of allophan -~h a high
ec,'chia:n capCa i y, o;t t ha i-v rie st'ly pyroclastic materials in the
sil t, sandI, Sa d jr- ei fr actionss"
According -,t tthe ., Si .So i S!,rvey Staff in Soil Ta;xo-omy (i9i0),
Andepts occur in or near mountains with active volcanoes from the
equal or co high lacitudes Andosols, therefore, occur ,.: .ly t ',o..h--
l-jt Lt= Pacific ,inj of volcanism '.4 inr volc'i c rc 1io of C 0 ELsi
Indies and Africa.
Luna (19s59) reported that in Colombia t:ypicil Andisols occur
most coi,,noily on gentle, slightly u:duidling topography betwen I 300 m
and 3,000 m abve sda level in the And.-s i;ounta;.' rnii j. Luai fu-her
stated that studies on volcanic ash '!is and volcanism in Sgnerai
were very l iri ted in Colombia. The i;pl icaeion was that expanded
programs in these areas would be qu; e desirable.
Var-ca (1963) completed a general study of soils in the Pasto-Rio
Mayo sector in Departamento Narino, southern Colombia. lie reportedd
chemical, physical and morphological properties for several profiless
collected fro: six irajor soil areas in the sector. The do!,i nant 0roup
of the six vaere soils derived from andes:itic volcanic aish. Vare
suggested that a large group of soils derived from vcicanic tuff had
"hardpans' cemented by carbonates and/or calcareous clay. Iield obser-
vation of these soils by the author aftiriro. thai the "hardpan" is
actually a duripan as ihe primaiy cerenting agent .as silica.
Wright (1964) csated that, even thiuigh Ar.,dsols occur under a wide
range of clin3atic co;ldi iions f.'cm lo,- to high lati :-des, the jross
i;or-hology of the soil pr.ofil es remains rather ul;iform. -!-' listed
several properties as co;rmon to Andcools throighout t'ce korld:
(a) deep profiles o.:'tn with distinct deposit;oncl stratification,
(b) thick dark surface horizonss high in negli;gily hiodegradable
(c) pi i r y I i ish br'o.mn ;u'':oil colors ~id. "' i ari :.ss"
(hixi x o n) ,
(d) low b il, densi ty i hinjh w.;.r--hoding and retention c paci ty,
(c) v.dk t I jctural ,a ilcgat:on aJn I ck of cuans on pod surfaces,
(f) lack oF I tickiress dor plastic Ly v.hern roist.
Wright also Ji cussed, in dtai l, properties of both high and low
latitude Ardosols. He indicated that at low- latitudes there is a
thcriIal scqrl: nc 4i lth altitude which imparts only faint morphological
trends to dte soil profiles. The following differences with increasing
terpern ture wrire noted:
(a) horizoa.lion progressed from AC to A1-A3-C to A-(B)-C as
n'oi s u r increased,
(b) topsoil colors changed from black to dark brown,
(c) weak qr-i:ll ar structure progressed to moderate blocky in the
(d) subsoil colors became redder along with some plasticity develop-
(a) organic riatter content decreased.
Very high natural moisture contents (measured on a weight basis)
cnd associated low dry bulk densities are comnion features of volcanic
ash soils (Swindale, 1969). Both total water and 15-har water contents
are high, however, and whpe nreasured on a volume bdsis, the values for
available water are not markedly different from other soils. When
these soi s are dried t,) i5 atmospheres or beyond, the shrinkage be-
comes increasingly irreversible. Gradwell and Birrell (1954) dis-
cove Id that if soi I samples ha,,e n pr'viou !y ai r-dr ied th re .as
a ,rarl' d dec rase in liquid 1 i it a; pl .as ic limit values as ihe
ol lophane content increased.
AnJosols, in general, have a very high total porosity. Ydioa-ki
et a,. (1963) reporLed a figure of 0S/ for Kanto loam, a predominant
soil around Tok;,o. Swindale (1969) stated thaL associated wiith this
high porosity is a high saturated permeability, a though these soils
are notoriously di fficult to rowet after they are dried because the
organic substances adhering to particle surfaces are generally hydro-
phob;c and the contact angles are large. Youngberg and Dyrness (1964)
published a range of 63-85% pore spaces for some Oregon Andosols.
According to Swindale (1969), the particle size range in Andosols
is quite often very large. He further stated that particle size
distribution data jre difficult to obtain due to poor dispersion
characteristics of these soils.
In general, pH values of Andosols rang. above 5.0 (hi lir et al.,
1968, and Flach, 1964).
Cation exchange capacity values for these soils are quite high,
Birrell and Gradw'l! (1956) have shown that this parameter varies with
concentration of leaching solution, nature of ions in solution, and
volux of wLatr content of the washing alcohol. G;rrell (1964) and
F'inik (196) poiitid out thla conventional CEC determination may be
subject to considerable I rror when applied to soils containing amor-
phous mineral cciloids and ali such determinations iust be interpreted
wi th caution.
Base saturation covers a wide range of values although pH values
S : i c, l ( ), i i t ibu ed ;o pi dep i -
Ano uu! s are kn 0.: io fix lirge quai ti 'ies of hosp'.ice, tolybJare,
ardI /th r i ili l rly sLruct 'rd nions. S~ uiin rs (1 59) a:d Mi l ler ot
.H. (1930) avi sho'n, for ;i i, Z.. li;ndl and C ,sto Rican 's i Is, respec-
tively, Lhat jphosplha is bound to a lumini, Blasco (1969) reported
d(t L for upla d soils in DeparLa, anLo ilri o, Coloh.bia, and claimed
Ltht inert plhospiaous represented about 52' oF tiha total P with rather
low values for other P fractions.
Andosols invariably contain relatively largyc counts of organic
maLLer in Lheir surface horizons. Kosaka et al. (1962) and Aominne
ardJ ;obaYashi (lS:64-, 196Lb) demons rated the negligible biodegrad-
ability of organic materials in these soils.
Eesoail (1969b) ipesented an extensive review of literature on
the sineralogy of volcanic ash soils. The sand mineralogyy of these
soils is composed mainly of prir'ary minerals such as ferron'acnesiums
(o livines, pyroxenes, and amphibolbs), quartz, foldspars, nmagretite,
and various silicate comply xes. The silt fraction may be constituted
of primary and secondary minerals. The secondary minerals, Ospecially
in high allophan.e oils, may be aggregates of cla/ occuriin9 as
psudosororphs of silt. ibbsite and hydrated iron oxides frequently
tend Lo accumulate in the fine silt fraction (5-2 -).
eesonin (I>6Sdb) wvnt into considerable detail regarding the
occurlircec and format io of various secondary minerals in the clay
fraction of volcanic ash soils. Allophane and halloysite were the
most prevalent species. Weathering sequences involving these two
members were especially interesting and will be discussed in greater
detail later. Under special environmental conditions, such secondary
mineral species as kaolinite, gibbsite, bohenite, imogoiite, montmo-
rillonite, hissingerite, vermiculite, chlorite, sericite, palagonite,
amorphous silica, aiiorphous alumina, iron oxides, and amorphous and
crystalline titanium oxides have been identified in the clay fraction
There is a dearth of published information on the n:cromorphological
properties of Andosols. Frei (1964) described the microfabric of a
black Andean or "Paramo" soil and a brunizem soil located in the
central Andes of Ecuador. The black Andean soil was derived from
andesitic volcanic ash and was characterized by having highly stable
crumbs which formed a spongy and very porous matrix. He speculated
that black cutans on ped surfaces in the lower epipedon resulted front
precipi cation of dispersed organic matter migrating downwards by
percolation. Below the epipedon in the B/C horizon, organans occurred
on all the primary sand-sized minerals. Frei also suggested that
perhaps colloidal silica acted as a completing and mobilizing agent
for organic col'oids with subsequent precipitation on mineral surfaces
at lower depths in the profile.
llejia (1971) concluded from fabric analyses of a profile of the
Corzo Leries (an Andosol on t.e "'abana de Bogota") that tiese data
provided valid additional criteria for the classification of ash-
derived soils. 'e outlined several unique characteristics the most
important of which wa:. the presence of an isotic plasmic fabric (see
"I ;r, r I I, f'or di scussio Lhi: t!)e ,' niL .ri lCno ogy osn
nric an lys is) i n tl A v; r hol i > z i"< id [ 0 t iL !, ic 1,1iisliC
fabric in i ho dccc-z;t .h ri/ons. This feature along wi ih characteristic
void p:5toris, i:t i niincr'.loI y n,/ d 'n range ii: nt, iand s ;d mil'ralogy
u, : ALed J i ni ,in r'ibrric rypo pi culiar io Andosols. rI "ji prr osCd
h n ic ., rica A.dicc" (A idic F b hric) For this Fabric class.
iaej ( r' intained, hiov v r, that rigorous statistical studies ovc.r a
wide range of Andosols iws needed before precise definition and adop-
tion of this fabric tpe could be realized.
Luna (1969a) mentioned the existence of a fabric formed by a
plasma of porous aspect and of isotropic character in a Typic DysLrandept
of Dcpartarento Antioquia, Colombia. The fabric type was Lentacively
designated as Amorphic.
As mentioned earlier,Andosols are characterized by low bulk
densities and low- base saturations in addition to high organic carbon
couiltnts and high phosphate aid water retention capacities. These
properties are to a considerable degree duc to high quantities of
-almohane (a disordered hydrous alumino-silicaLe) in the clay fraction.
The unique cualitiis of allop :-ne in contrast to the more common
orde-red alumino-silicates present special managrmen problems involvir.g
Due to the widespread distribution of volcanic ash soils and a
well-developea science of pedology in Japan and aew Zealand, consider-
able research on allophane has been undertaken iin these two countries
in the past 20 years. This review will outline and discuss ajor
portion of this research in addition ao accompli; sh enLs in ot-:r r.eas
of the world. Use of the tern 'allophane" will be restricted to
pedogeneLic disordered hydrous u luino-si icaces derived frow volcanic
ash, generally of an andusitic type.
Structure ard Comrposition
Ross and Kerr (1934) were probably t:., first workers to present
significant data on allophane. They reported for geologic allophane:
(a) variable chemical composition, (b) variable index of rafr-ction,
(c) no definite crystal structure (lack of sharp X-ray pov;.-dr peaks),
and (d) no regular molecular arrangement as interpreted From infrared
spectroscopy. Ross and Kerr referred to al lophane as an amorphous
alumino-si 1 icate and i ttle more was ascertained as to i ts structure
until the 1950's when Japanese and New Zealand ipe'ologists began to
explore more closely the weathering sequences of volcanic ash clays.
Advances in structural knowledge of allIopTer-e came haout through the
increased use of techniqu-s iuch as X-r/y an:d electron diffracromitry,
differentia l 'rrral anaysis, iinrned spectroscopy, and electron
Throughout the !i 3 s and ear ly j1,6's,,seaer3 investigators
disco-/ered that al ophane in -.,,.ic:anic a-h soils could exist in a
structural continue iirl bel ow the "rcl i ci.i cr s talli e puri ty" of hal oy-
i te or ka li:ite. Fields (i935) ir-nicated. a weathering sequence of
i creasingg crystal l ni ty: allophane B --al loph3re A .-methal loy-
site. Yoishnaga e s Aoc inna (1'62a) ca;i,..d to have dlscovcrad a more
crystalline alc mlia-r;ch species wi ih fibrous morphology which they
called "imogclite." Later Acmine and Miyauchi (1965) through the use
of 1iy d I OL ol :Ar le to
iIo a 0 !.o l i lite:" A J 3. "le'golite 3"C 'T s sup--
p A 0d to r "!" -! a "913 crystelli,,, stage LhU "i liic AI"
y 'a (l'";) ';-, n to r', acir se tp, sp-ci ici .y of al Icphn,; struc-
e '; h, infrar,, a:- ion with dI oleri.. (0 o) ex-
i. f hy). ../ glo up (?;l - O 0) at roo.i ii;r; i a ura e o OOC.
This : ','s one a c:,iparative basis with ian tmorillonile anr. hydrated
halloysite. ;I four that all the OH groups in alloph.ne could be
replaced by OD,F'hile vury ;minor and parltal reply acemen ts resulted for
montLinri I lon ie and hal oysite. Wada concluded that a sharp line
exists between structural OH groups and absorbed 20 in aillphane.
Uada (1967) dhen sur.marized chemical, infrared spectroscopy, and
rorphological data for soi l illophane and suggested two end-inembes
.ith chemical composition 2SiO2 e Al203 3H20 (allopha,,e) and Si02,A120
H2 0 ("i 3r-ol ita") along w i:h a structural scheme for the two end-
e:;,bers and inter:edia'e coiipositions. HIe proposed a structure for
allophaone wi th a 1:1 Si/AI ratio composed of 3 si lica tetra!.edral chain
and an alumina octahldial chain sharing a corner of the respective
tetrahedron anj octc hedron. Addition of another alumiina octaliedral
chain to the silica .etraheidral chain results in formation of alIlophane
with a 1:2 Si/Al ratio ("i rogolit':), Wada reported that noncrystalline
and poorly crystai lna X-ray patterns oi alilopha-.e with a Si/Al ratio
1:1 and 1:2 could he interpreted in t"iam of the differences in the
case wi:.h ihich the respective unit chains are aligned.
App3arintly there can be considerable substitution of Al for Si in
tetrahedral co-ordination in alnophanae which deelnitely segregates it
from halloysito ai d k'aol iicc. iada's (1367) scheme claimed to predict
the trinsfo. :ation of Al co-ordination from 6 to 5 upon dehydration
and further to 4 upon cehydroxylation.
Russell Cet a. (1969) presented supporting evidence for the
uniqueness of "ii:ogole i e' khich they believed .,arrdnced i ts cilas;i iica-
tion as a distinct mineral species. They interpreted electron diffrac-
tion patterns in terms of repeat units 8.4A par-alll and 2A perpcndiic-
ular to the fiber axis. They proposed an alternate structure to that
of Wlada's (1967) for "imogolite" consisting of discontinucus distorted
chains of Ai-0 octahedra linked through isolated Si20 groups. They
contended that the existence of the Si207 groups was supported by an
infrared absorption band near 930 cm-". They reported composi tions
of 3 SiO2 2A 20 3 0 5P20 and SiO 2 Al203 3H2C for "imoyolite"
and al lophane,respeccively, somewhat different from /ada's formulae.
X-Ray Diffraction Data
The presence or absence of X-ray diffraction peaks for allophane
would, of course, be highly dependent upon its stage of crystal inity
between partially weathered volcanic glass and hydrated lalloysite.
X-ray data have been presented in numerous papers generally as a oub-
Separation of the clay fraction (<2p) into s;,al ler size ranges
has usually facilitated diffraction in/estiga tins of allophane.
Yoshirnga and Aomine (1362a) showed that the 2-1 pi fraction of a Uemura
soil -rhibited seve-al distinct di fraction peaks indicatingg the
p esence of quartz, c'is obalite, fcldspar, and gibbsi e. They were
able to isolate "imogoliite" and allophane using-di fferential dispersion
properties. in the 0.1 ;r fraction, allophine displayed no diffra:cton
peaks or bands (X-ray amorphous) while "imogolite" gave distinct dif-
fraction bands at 4.5, 7.6, and 5.5A.
' b 1 'icrr ,opy'
i (i1 ) 1i d 1 t l .r ,: ,-c : s 1 alloe n ge
Srili ly s I a eJ fluffy a5reg wi th a rc',rdJ d r d! l,"r i-iearac-:e.
Yos'i r giy and Ao-ie (1962;i ) Jscrib-d ";V ry i.tp o glo'>>i's"' ile
Miy, : (1969) 'oh!i .v d 7.r.y "fibi us ': uters" whichh uI i ild in retro-
spect probably be ;ni fid 'as "ia5i oie." Yohiinap and Aomrine
(1i62') observed thread-- ike particles of relatively uniform size which
Lhey tenta-ivoly identified as "irogoli e.." Wiadd (1967) sunmmar;zed
several observations by ird ica ti n that a fairly good corre la ion
existed bel'ween iworphology and developing t of structural order. He
stated thit "imogolitc" developed smooth, curved and often branched
threads \with diameter 50-200A and extending as long as s'eeral microns.
W;th an increase in the Si/Al ratio, the thread-like tendency gradually
diminished and minute particles (50 to 500A) in aggregated masses or
thin film s baca-me dominant. The fibrous morphology of "itnogolite"
strongly suggested one dim'nsiona! regularity in structural organiza-
D fferential ThermT l Analy sis
Yoshinaga and Aomine (1962a) public shed thermal data on several
soil allophanes. They revealed no marked therm il reactions wit Lh the
exception of a strong cndotherm between 10-170C adsorbedd H20) and a
sharp exotherm bet^eenr 910-915C (fort,:aTion of gamma-aluminsa). A
sluggish exot.herm was nole-J just after the endotherm which was assumed
to be due to tightly bouod peroxide-resistant organic matter.
Thar.,i l a:s;alsis of "irfcogoiite" by Yoshinaga ar. Aomine (i962b)
displayed the early endothenr and late ex.otherm of allophane, cnly
they occurred at temperatures 20 to 40C higher along with a more intense
exo thbrm. In cJdition, "hia olite" exhibited -, endotherra betL,;en
425-435C, indicating driydroxylation.
Miyazaw!a (1Yi2) reported a sharp e.xother!a c 850C for clay From
a hufnifed all9ophlnic soil of Japan. This appeared to be a somewhat
lowi nucleation temperature for allophane.
Miyiuchi a:.nd Ao.mine (1966) indicated that DTA curves varied con-
siderably with 'exchangeable cations, especially for the high temper-
ature exotherm. They ranked the cation effect of this exotherm from
highest temperature to lowest in the following order:
Ca> K > > g > Na
Campbell et al. (1968) revealed that particle size, pH, and organic
matter content :had considerable effect on the thermal analysis of
allophane. They found that the area of the low temperature endotherm
and the height .nd temperature of the high temperature exotherm in-
creased w;ih decreasing particle size. With increasing pH, here was a
considerable reduction in height and sharpness of the exotherm. Removal
of organic matter had the same effect. The authors concluded that con-
siderable changes in the high temperature exothermic peak of allophane
could be produced by treatments often used in the separation of
amorphous colloids from soils.
I n f red Spectrosc.o-
Infrared absorption spectra maxira For clay minerals have been
generally identified as follows (Grim, 1968):
F-eg e Lgm ...i(J Absorptior due to:
3,500 3,700 -4 Cil groups
1,300 1,90 6-10 -1adsorbed 1120
400 1,150 8-25 lattice vibrations
Several investigators such as Lai and S-Cindale (1969), Yoshinaga
A (la i, 196?T ), i V ti-'c Os '- d F. ik (i' ) reF ried
r, -. 1 '. o;- i :i r. .J n ': xi Iy 3 c "1, D, 0 c i 1-,
J 930 :-"1 d< e .o hydro,/yl rou s, ab o- ,J H.,0, amd Si--0 or '5E -0-
AI -nd vibr ion r re pecti vely
U ( f (19 ')w I ",LOe lo o-cor I i i bU-ic dif !rtnc o bEc-w.en
i"ir te" and aiu' p ',; in Si 0 s trcthi n band. Allow phae' a i ith
Si/AI ratios of 1:1 to 1:1.3 displayed broad absorption naxima at 1,0!0
and 9':5 cml1 while "i aogoli Le" (Si/Al = 1/1) had rather w.l el l-d fi ned
absorption maxiri at 990, 955, and 925 cm-1.
Lai and Swindale (1969) reported that for four Andosols of Hawaii
and one from Japan the main infrared absorption band shirl'ed froia
1,100 to 900 cm-1 with increasing v.'aight ratio of A20 3/A1203 + Si0O2
This apparently reflected a change in state of Al coordination. Cation
exchange capaci ty and infrared data together suggested that soa
stabilized AliV 0 Al bonds occur in allophane minerals.
DchyI.r tion and Rhl'dration
loc,'gral dehydration curves of aIlophare hive generally been
ob-served to be qui te smooth (Girn, 1968, Yoshinaga and Aomine, 1962a,
1962b); however, Yoshinaga and Aomine (1962b) reported an inflection
for "inogolite" indicating rapid dehydration bot';cen 275-350C which
was attributed to structural H20.
Schalsa e a!. (1365) reported that air-drying of Chilean volcanic
ash soils produced sigaificanr Irreversible changes in CEC, soluble Fe,
and P. Air drying has been ecpo lted by many workers to cause formation
of pseudomorp s of sand and sil t which became difficult to disperse.
This gives sore indication of the rehydration properties of allophane,
Aomine and Yoshinaija (1955) '-ported that echylene glycol ritenL;on
was high for their allophane samples; retenLion by unheated samples p 'as
si milar to that of montmori lloi e, but heated materials gae valie-s
higher than those of heated mnontmori l on!it.
Orchiston (1959) indicated that heating of allophane considerably
increased the area available to the water molecule at mono-layer cover-
age. He further stated, from a comparison of the surface areas avail-
able to water vapor and nitrogen, that some allophanes may possess the
equivalent of internal surface.
Clay contents of soils, containing varying amounts of allophane,
were calculated from measurements of surface areas of separated frac-
tions using adsorption of nitrogen, acetic acid, and water-vapor as
methods of measurement by Birrell (1966). Values for nitrogen adsorp-
tion ranged from 29 to 320 m2/g of surface area. Since these clays were
not pure allophane, the above data should be interpreted with care.
Allophane is optically isotropic with an index of refraction close
to that of glass. Discrete clay units are unobservable in thin sections;
however, due to the anisotropic properties of layer silicates, their
overall orientation relationships can be observed and interpreted pedo-
genetically (see Brever, 1964).
Luna (1969a) reported mainly isotropic clay in thin sections for
a Colombian Andosol; however, Luna (1970) indicated thb.t as allophane
weathered to a relatively nore crystalline state, it also gradually
tool; on some anisotropic properties.
Steen and Fryxell (1965) stated that weathering has had little
rdi il .r i. lfl on 'hi val,-.s of !'9c i. 'l-x of 1 f r .;c )f pumice
I I S :,:' 1 1, ;, j, ard G I 3c i ri Fa k.
,)s Jr i Kcrr 1934) oi 0) rvcd a vir i ble i -icx of refr.actonc
( .';72 1- i .' ) ior al lophn
I on E:. c i d emotiorn
fhi ion .xch.ino i oprt ies of allohane p-i:e Andosols in a
very unique nanig','- t position. lon exchange capacities of allophane
are highly pH-depcndent.
Ao-1ine and Yoshinaga (1955) reported a CEC (at pi. 7.0) range of
23-51 mraq/100 g oven-dried clay from three Japanese Andosols; however,
Girrell and Gradwell (1956) published data indicating that conventional
CEC methods were not necessarily appropriate for allophane.
'.ada and Ataka (1958) then shed considerable light on the CEC
and AEC pH-dependency of allophin e. The CEC and AEC values were
n terni ned with Hil, CI solutions varying in concern ration and pH.
Two adsorption mechanisms were discerned, based on; pH and equi ibrium
concentration. They found that the higher the pH of the solution,
the more cations adsorbed vi th the opposi te true for anions; also that
tahe higher the concentration of I Cl, the greater was the apparent
CEC or AEC.
Aoriine and Jackson (1959) claimed to be :ble to use "cation
-xchlage capacity i delta value" (ACEC (: EC pH 10.5 CEC pH 3.5) to
calculate allophanc content of Andosols.
Fieides and Schofield (1960) reported on two allofhanic soil
cl-ys ,*ich had a net positive charge below pH 5.5 but acquired con-
siderable negative charge between pi-1 6 and 7. They postulated that in
allophane, because of its origin From glasses and disordered feldspars,
octaiedral posi> -ns .ere icrc'ing and its ch)arce tic var bile
charge was atli 'bca ad to the J'-iavicr of speci ic sites origin Liig
from bro'-en boiLs of Al in ittrahedral co-ordination. In l!ht of
Wlada's (1967) observations, octa Idral posi tions inere ,-ot r ccssarily
lackingg", esp: cially in "imolgolite." It could alIo be that h'ie a .tnit
of tetraharaal alu.ii nu.m, as less than that inferred by FieldIs and
Houng et aL. (S566) published data indicating that the pH-dependent
charges of allcphane were more likely due to dissociation of surface
hydroxyl groups associated with silicon atoms (silanol groups), and
that permanent charges were probably due to tetrahedrally co-ordinated
aluminum in the a!i.mino-silica network. They further sugay5sed that
the amount of exchangeable bases should be expressed in terms of per-
centage of the permanent charges, since the pH-dependent charges were
considered not to take part in the exchange reaction under normal soil
Aomine and Egashira (1968) reported flocculation of allophane
occurred 'ith a relatively snall arrount of divalent anions such as
sulfate as against ironovalenl anions. Their results indicated that
allophane w!as positively charged at the prevail iing pH of Andosois,
unlike the usual crystalline soil colloids.
Eschena and Gessa (1S63) showed negiti e charge density of
allophanic clays calculated from permanent cation exchange capacity
(CECp) as lower than that of bentonite and kaolinite. Heating For
2 hours at 400C ruduced pil-dependent exchange capacity (CECv) and
specific surface, but had no effect on CECp. Tan (i~5's) useJ CECv as
a criterion for classifying the Andoso!s of Indonesia.
I ( 1 ) v ,ti j). r ic f)01 :,ho h,' wi 1 h 1 1oph nre.
;'; ''.0, O,,i. . ospi- )2 '" ] :ci J r 1 1h r r .pidly
i a lloph :- ilo r i n r," )l'b i ,: a ; hi e pIH 7.0, the
ri',- ction c i t- b: I is il lustraicd !h i portsnce of
p',., ph ia il 1on in lade. aly -icid An:ioso' s,
Adosois typically have thick dark A horizons hii.h iae hii l in
organic matter. Org--.ic mrtier accu;iuleatlin takes place rapidly after
new additions or volcanic ash and is exceptionally resistant to bic-
logical deccon,;,osition. A series of .Jpanese paplars in the i,-rly and
mid 1960'5s wi.re concerned with the relationship bet.c.en a lophian and
d-cor positionally resistant organic matter of Andosols.
Early paper by Kosaka (19f3), Adachi (-i963), and Tan (1i9l +)f!
I ndoo sia vcr- concurred vwi th humi ficat ion s cci's and hur:ic-fulv c
acid conLIents 'rcm a soi clasi Fication viewpoint. A series of aj.b-
licaLions then fol 'ou.ed on specific allophan-organic reactions.
Aoi ino and Ko'byushi (196!! 1965 ,)) found .hat a:lophane inhibited
the activi ty of protease, cC- cnd -a,rylases, and cellulase enzymes.
Aliophaaie sere -d to adsorb enzymes at both positive and negative charge
Polyphncrols '.re found to undergo rapid oxidative changes in the
preseaice -f a; lophane according to Kymia and Kawaguchi (1964). Non-
bi:loi!ical c~taly'ic oxidatoin appeared to be responsible for the
changes. These polyphencls could be cdsorbed by ailopiane and calaly-
tically e,;d!ied to give dark-colored, highly acidic polymerized
produciLs similar to humic substances, regardless of the acid environ-
ment and low base status of the soiI. Tannin-rich qguercus sspcies are
ofien aound anong the vegetation on Andoso!s.
Kobo d Fujisawa (196) c]ai,'ed that ai lophane showed preferen-
tial adsorption for different types of hod;ic acids. Toki;L o, r end annoo
(1i65a, 1S65b) reported that in Japan, yoi.ng Andosols ha -e lov.er u 1 ic/
fulvic acid ratios than older Andosols indicating that the concentra-
tion of hunic acids, the alteration of fulvic acids to ht:nic acids,
and the carbon content of the so is increased wi th developsren of
pedogenetic processes, Based on their analytical data, they c!aii.iod
that most of the hurus jas bound with allophane and sesculoxi'des,
especially aluminum. Humic acids were characterized by high darbor
contents and high C/H, C/N ratios while fulvic acids had low carbon
contents and C/H ratios.
According to Tan (1966), Al and/or Fe will migrate to lo-.er hori-
zons depending on cho humic/fulvic ratio, In Latosols, A! appeared to
be mobilized due to the large amounts of fulvic acids pree-.t whi le Al
and Fe were both robile in Andosols due to the presence of both fulvic
and humic acids.
Pedoggentic ,ea l then g
Under well-draired, i.oist conditions, the weathering of volcanic
ash may lead to formation of i3iy different secondary minerals. Besoain
(1969o) claimed that under humid conditions accompanied by good drainage
conditions a mineralogical sequence front allophane to knolinitic type
r!inerals alnmot invariably occurred ji ih Li:e. The incidence of allo-
phan- and/or kaolinite type clay ,,i. :- a s in arid envi ronmeii ts i s rare.
i'ieldes (1955) stated that andesitic volcanic ash developed in
time, che folliowinq series: Allophane (6, A3, A) --- halloyi tc/
me tahal ioysi te --' aoi i ni te.
3esoain (1969b) suggested that the inclusion of kaolinite was a
logical bu' LIeo. Lical ai sibilily si; ce e, a d soils con-
h l loys i e.
Fi eI :s (l 5) o tlii d A b ril strucLur-l col ti u rii r rhe
.Iove-r ti ...... 1h riirg e .e;'a : ( ) allop hnn> 0g in which .r ';oI
;ilica ,i3 di crc tnd cl y partitcl s ul ra fine, (L) Allophaie A in
whi h alumii'li and i I iica v 'wre randomly colii')ined and particle si ze was
greater, and (c) nctaihalloysi e in which alumina and silica are coiabirned
in a kaolin structure.
ilay (1560), on the island of St. Vincent, 8.W.I., reported that
andesitic ash originally consisting largely of glass and the minerals
anoirhite labradorite, hypersthene, augite, and olivine had altered
to hydrated halloysile, allophane, and hydrated ferric oxide in 4,000
For Ha'.:aiin Andosols, Swindnle and Sheri an (1964) indicated that
in the early stages glass weathers to yellow, brown, and orange
palagoniteC (Ca, Mg, and K containing amorphous alumi no-silicate) due
probably to hydroxylation and physical breakdown. They said that glass
contained much strain energy; consequently expansion due to hydroxyla-
tion increased the strain, and physical comminution occurred as a
strain-relieving mechanism. Some removal of alkali and alkaiine-earth
caLions undoubtedly occurred simultaneously with hydroxylation.
Ol.nrasa (1964) outllined what he conceived as the weathering
s'.a:ue1nco of volcanic ash in Japan: (a) leaching caused immediate
neutrality of acidic new ash, (b) large amount of bases are ieieased
to a great depth and the ash becomes alkaline, (c) freed bases are
i .h ,d quickly along with Si due to the alkaline or basic condi tions,
S h S i s s a ,d --iLl- s occt (d) and Al are w-e-k y i'5incd
,n t C._ b a-inr in" but later 3a1 i;: c j;-aduaily forms, ia d (e) .ilopine
gradually crystal ies to I-yl'ra d halloysite ind, in soie cases,
Fields (10G6) co: silered structural randomness in hydros al: Liino-
silicates as being highly significant in the formation of ailop't ne.
He outlined four possible mechanisms of al !ophane formation in soils:
(a) weathering of basic silicate minerals dissolution of discrete
Si tetrahedra occurs under local alkaline condi tions with subsequent
reprecipitation with Si and Al ions under more acid pH after leaching
of basic cations, (b) weathering of glasses direct formation from
glass, (c) weathering of feldspars the ability of feldspars to aiter
to sericite apparently depends on the proportions and ordering of Al
and Si in 4 coordination. Thus in suitably ordered fe!dp.-rs,
single chains wi th Al -- Si order identical with feluspar ca.: detach
from (100) and (010) sunfac.es and polymerize to produce mica sheets.
Feldspars in ,which A! and Si have disorda,-d arra-gements such trans-
formations are not possible, so that sericitisation cannot occur and
a!umino-si licate weatheling products of such feldsparts appear as
allophane. Fields claimed that this process occurs during initial
weathering of feldspars from iNew Zealand volcanic ash, and (d) grinding
Kanno et al. (1968) claimed that aliophanization of glasses
proceeds through desilication, hydration, and replacement of Si-O-Si
li-ikaes by Si-O0-Ai linkages.
a3iN 3 et al. (1368) recognil.'ed a weathering sequence from ;luophane
to halloysite i ia Coioibian Andosol, while Luna (1969a) also recogni,-:d
alloohane A ar-d 8 In Colombia.
3r-main (1 ', ) (U .co pr a '- ,r, .parl p a 2 a "dolil'"
C'iil ; :l' ; ic ,--. A idools caLS-in
"i! o.ol i '" 3 I :I, n i p arc, .pci clay r A cLi on r ,IJ ih L its
occorr cce i f ro! I / I'ltei to i the :i pn -,nt oi Fi i : re 2o ordered
Utili gI i ; n ied in this litera ure review, V ii
l01 ph< (19/1) repoiLed ihat im bers of a recent amorphous a!uiiio-,
silicate w\orkhlop in Japan agreed to the Foolloini tentative defini tion
of ill ophane:
"Allcphanes are rm i:L:s of a series of naura lly occurring minerals
which are hydroja -l.i]:,'' i lic-ites of widely varying chemical con-
position, characterized by short range order, by the presence of :i-0--Al
bonds, and by a differential thermal analysis curve displaying a low
temperature endotLherm and a high temperature exot'ierm vli th no inter-
med Lte endo Lthrr."
i-LA E. IALS 'D3 I, THODS
Site SLi- action
Soil profile s ies were selected by investigitic,, of -ivi hle
iarial photographs in Bogota and an initial land recoirai sanca of the
Narino area about one month before actual fe!ld work co,:e-ccj, It
was decided, after observing ;Nari ,u Ai.dosous occurring ':iaely bet'lcn
2,000 m and 3,500 m in al titude, that meaningful pedogen:tic data
Lould be obtained by profile selection in an a!t tidinal sequence.
Profi le locations in the Departuento of Narino are shown in Fiy.
i. Profiles !io. 1-5 were selected at altitudes between 2,000 m and
3,200 m within a 25 iki radius of Volcano Galera (Pasto) in order to
ai low tihi assunprtion oi ash-proi ncc uni formity. Profi le 6, represent-
r, ..he higl.est altitude investigated at 3,510 m, ,'as near Vc!cano
Cjti!al about 80 kra southwest of Galerss, SiSusti tuition of tiis si e
--s necessary because chick ash Jeposits do not occur above 3,500 n
on the flan'ks of ial eras. An assu'mptior was made that ash nincralogy
,.'as noi o\e,- dissinmlar in 1hea Cumbal region due Lo predominance of
-.jsi te tholrougihcut t.eo uplards of Marno. These six piofi ls ,.sre
r-cside-ed Lo Ieprc-senr app,-o:.'iiately the maxi u,! ringe cr weat a :iering
s',e i-ty exe-ri ,i-ced by loessial pyroclastic deposits in tie a;tiplano
or lr-no. Factors supporting this ssurrption will be discussed :n a
Profit i 7 was SrTpLJ 57 kic, nr, c::heas t Of ; iers in the vicinity
o, Volcano Dona Juare at 2,G003 a for comparison purposes with profile 1,
DSIARTAMEN TO OF MAPiNO
V.G T, l s, M6 1
Io o," Caho 1e
Fij. 1.De partame to ofr Nriio I]ocatd ip sout!.este rn
'Col biAe, Smil] inst numbers Adic-ate loca-
tions of prof; es 1-10.
tions of pro. Fles 1-10.
i 3-'ofi 83 s'pled in a lJarg valley I(Sbana de Gunchcal: )
pro i 6 ; : e pirpos cf cr.r; n ininI the : n lu nce ci ..jlcinic
activist on all u lo- -l u rin's s il ;iLhi n th s udy ar .a, Pro miles
3 and 10, altihoioc'i .ro'hlc o ic-illy similar ] o Andosols, W:epre Found by
h!F field 'est to be lo:, in all phane. Obviously, these soils nr rited
further ir. t i on,
All soil profiles :a.-r sampled 7rcm road cut'. Descr options ,ere
a.ado and samples cotalned dfter rriosal of app;oxirately 50 to 75 cm
of soil iate'ial] paralla to the profile face. Profile descriptions
for all i tes were mrade in accordance wi h criteria described ii, t:ha
Sol; Survey iMarlual (Soil Survey Staff, 1951).
3u k saimpes (approxi.;:ael one-ha3 f gal I ) '.*"-e co l i-::ted from
each horizon ad replaced in plastic bags. Undi iturbd ccre sa:; les,
epproxiia Le ly 8 cm in diamicicer, .:sere col.l ?c'd fior.I s'eicted hSori ons
of most ioi ls for ,ulk density mieaj-ji events.
N-atrai ly oriented clods were col lected f o.l ; ele) t major lo'-"
zons of prof'Ies i through 6 for Cthn Jsetion analysis. These speci-
nc!Ts ',,er- placed in labellpd ne'tl Lins .i ;h ',I c ri ietln.aion mr'rk-d o0
the containers. Sjlops wr re determined by use. o. an Abey level.
tPrttcle Siz Dilst.ibuJtiolu
Partici C si.e l e.te rination.Ca .as b a .odli fiid hydi-c.etet :eth'od
adcpei fr, :m ouyoucos (1926). Organic atteta, ,J:hcn pr-es. t, wtcs
p* ,c 0ed prior t o rialys' s usii;, h/ydr-9n per; d Thf. d i
3 -7. u p-IK pL '- i I i i c ilfc!r lat i on
'j t U. S. D ,- r t .; ,,1 2 ,- i, 1, cl. s i' ca lilonl
( I I l i r C it.
,ii DIe ity
T io s a ,dificn tio o, f : o a r l outlined
y 31 k ( 19 '). S i c coar s s ci! ton con t' n L s vi tir al ] noi-
eisLcnIt in h' i!,':ino Andosols, the core rrii'.od was col-siderilcd to be
a sai ai act or :.' i: iq ic for bulk densi ty du; rmi nation.
Fif oitn-lo sOsre ict-or Conteit
This dcteri.lj ira tio in .ws nade according to the r tr-iod ouc'iined by
the U. S. S.liniLy Laboratory Staff (1951).
Chemic a M methods
. '.~. g:j ,':_i tat cis t
A soi -I:ol tion ratio of !:1 in distil ld water and, in 'os0 cases,
I N ,CI -as i.a srAd by a ecklan Mot;del G ipl meter.
Cat.ion nExa' ."ntr P C. '
This paF-ar' ir is dctrni ined after the Nrthed of Bower et al.
(i:, 2) usingj I l ven ,;it niul, ,s.eti:te at pH- /.0 as leeching ac enr,
Thies ccr,,,!nts ve-e da 'tr'.i-ined '.pa -ait ely using the EDTiA method
oi: darros,, aind iri'pso (i962). Tenl giram of air-dry soil was leacihd
with 0i 0 in of ',IAc. c at ptH 7,0 as described in Pech et iL. (19t7).
An aliquot of the N l,OAc leachate used for C--Hg determination
was .- ayzed for petass i I: aing a Coleman Jr. Spectrophoc e.- a
Ex chan e ble SodL -im
An aliu ot or the NH4OAc Ilachate used ror Ca-Mg d'torf ,innation
vcas analyzed f sr sodii'l using a Col.: ,ian Jr. Spec trophotoaiTiecr at
This was de ermined by the Walkley aid Black (1934)) method.
Elxchageabhe Al'.rmi num
Exchangeable aluminum was determined by ili fluoride tiLration
method of Yuan (1959).
Free Iron Oxides
Free Fe203 was analyz.J d by a technique reported by Ching ~a al.
Disrersicn and Fractionation of Clav
Portions of the so l samp es in plastic bS: .ra .'einoved a. d
allowed to air-dry, -hile the remainder was i-ai stained at epproxi atiely
Field r oist re. This .-as ado.e, because An:dusols, upco drying, oItun
form sand andn sil I pse,'domophs o f c!ay particles (Birre i, i964). This
oulid decrease tremindoansiy the a61ount of ci iy that might be dispersed
( right, 19 6LS ).
Duplicate 5 cj9 saples of soi I fromin each horr'zoi. ,'ere piaccr in
130 ml poiyi thylene centrifuge tu aes A; r--dry surface sa.:p leas r;t.'
i l I l.p i b blh ouE ,. t o ro i'g t:c r :d to r etain
'ici1nt ii ,s ri err e Aible i and At' ;' t io r,
Iu U', i, o !,zi ors '. k ac !< t? ppr I" y ) icd .0i :> ure si nce
in most c Is s s i :. irJjcr ibe in t e 28 ;d C h ori ns, Organic
a. t ,U 1 i ; I 'or sur face' 'or i ,.ois by ;i (r th [ t oI L vk' I i ch
)d in, ,s (19 u) t i'S o j codiul- hypochiloi it e solutionl adj ,st d ,. pH y.5
by 1.0 N HCi I i; iately prior to use.
T1n m ili liitc s of NTOC solution (mini r um 6% uvai labie chlorine)
wa!s ad1d'd to each noi [ ia1le in the polyethyle.,e Lubes. This fwas
repeated fou.- to five times, hating the suspension in a boi ling water
baih [ r 15 minutes during each treat, !ent. The supernatant .-.as Ic-
canted after centrifugation. Surface horizons treated in this manner
t.are qui te v.ll dispersed after completion of ianOCI oxidation.
Consicdrable amounts of aluminum oxalate and fertic oxalaite com-
plexes in peroxide extracts of soil clays have been reported by Fr.-nler
an!d Miltchell (1963), especially in soils containing a higqi amount of
nallphanic colloids. Since Andosois contain large quantitri s of
1 loph.ane, whhich is quite v-! cablee to common pretreat-;unts such as
organic matter oxidation and free ilroi oxide removal, it would ba
cdvantosrous to :.i i, i~iz possible pretreaLimenL -efr ccts. Therefore,
iron oxides rcc.-,' not -enmo,/ed ard NaOCI rather than Hi22 was used oa an
oxidiz'ing agent for orin c matter.
Subsurfo.ic s-.iples .cere di:sl:ersed with 2% Nl.2CO3. Approximately
5 9 of roist 0sil P;as placed in 100 ,1 polyethylene centrifuge tubes,
Twent mi ii i tit ers of 2^, Na2CO3 solution was then added to the soil
samples ard the s,'spcnsion ',as stirred for 2 minutes. The less than
2 p frtaction was rtl!on scpara ed by centri fugi ng as described by
thittig ( 9J5) o. :ently, the less t 2 2 p 'etion :s ,-rated
into 2 0.2 ~ and less than 0.? 9 i frac ,. s by centri-. i 'uj i.
X-K- Di ffraction
Clay suspeqsions representing the 2 0.2 pj nd less i0a:. 0.2 i
fractions v.re placed on cermic tiies after the ,.:thoui r.', ;:;. and
Diamond (1956) as modified with the use of a suction apparatus de-
scribed by Rich (1969). The initial treatment pr;or to irradiation
was saturation by r-agnssiLun (I T.SCC2). The tile with plated seriple
was subsequently irradiated, glycerol so!vated, irradiated, washed \iLh
methanol and water, saturated with potassium (I N KCI), irradifaed,
heated to 50CC tor Ii hours,and then irradiated once more. In some
cases, the sample was hated to 100C for 12 hours after KCI satura-
tion and irradiated prior co 500C treatment.
Obtaining and storing the aforementioned oriented clay specimens
presented somn problems especially for the fine clay ( <0. 2) samples.
There was a te.defncy for the fine clay to be dra'.:n through the cel,-.iic
tiies under vacuum, This was alleviated by concentrat:n9 and flcccuiat-
ing the suspension .i th 1 TJ MgCi2 prior to applying it ro the tile.
hininmum water washirgs, usually equivalent to volume of llgC1, used
vuere necessary; otherwise, the problem arose again, Crackin g -;nd
fiaking of the fine clay speciiens of the tiles, even in a 100C glycerol
ai.,,splphere, Is:o created difficulties s. Thi: was ce,rnered in ,ost cases
by Lho-ough satur ation ith a 30% jiycerol solution dcra'.i through the
clay under sucticn,
Potassium-saturated samples ;:e re irradiated irmediately a ter
treatment with I N KCI. Anticipl.ting the cracking a-d flaking bronighc
on by dehydration and dehydroxylation of allophane at temperatures
v, r , d I i r o .' J d'y ik ..! c .ile
1 c. Wi h a very feI ,:C i ns f' or '0s Clay
of l 1 cCs for to rse cl y (0.2 2 ), i't iipos-
t u L i t t I for irradia. icn witho t losing all of the
Sle ii, i i'ic l iy 3si ci r i.cvenlid by i thr of '.o rietiods
'liic' s c orl : iually :ll. Double stick Lransp i
i: i Ald in < glass slide and LIhen pressad onto the dry, loose clay
filkc s lying on 'he ceramic tile. The glass slid' could then be
placed in the X-Irny isam path. The second rcethod wms som0iihat io:0i
ti e consuiiing. Ic involved transferring the clay From the tile to
a, agate mortar and pestle. The sample ,as then gently ground in a
srcall .niousit ovf wi'er Intil miost of the aggregates were coirpie'ily
broken. At thi s Lir,: the suspension was transferred witih dropper
to a glass slide end placed in an oven at 100 for about 2 horse.
Aftar drying. the clay was irradiated.
X-ray d i'fraclegrams '.?re obtained utilizing a Ceneral Electric
XRD-700 insLruci nt. Radiation was detected with a proportional co.ntlr.
i19-snturated tpcci':ens were X-rayed from 3 to 320 (2 0). IMg-saturaLcd-
glycciol-solvatad, 1,-sa tu.-ated, 1OOC and 500C treated specimens were
irradiated frocn 3 co 150 (2 f). Instrument conditions and settings
were as follows:
iadiation: Copper K alpha.
Fi ter: Ni cke I
Potential: 25 KV.
Current: 25 rpa.
Gonioaeter scan speed: 20 (2 0) per minuLe.
St.ip-chart drive speed: 30 in.ch s per hour.
i.ulse h.t selector: L =
Scale e:'pans7on: 600.
,ro oF Fset: 20.
'oC-ii '/i -1 li L: U.' .
Serene El its: io.
C'ot:ir t.be high voltage: 2.25 KV
A,|ii fiber ratemetor: Time constant 2.5 seconds, range
2 5 ;mal fier gain 16 low pps.
TaLe--of angie: 30
i fferentTal Therrm'l Anilyvsi
Portion; of the stc,'ed fine clay and coarse clay suspension were
transferred to aluminum neighirg pans, dried at 'OC, and subsequently
gently pulverized in an agate mortar and pestle. A 100-mg portion of
the dried sample .as then transferred to on;e of the four sample positions
in the insert no d.:r of the Deltatherrm tnermoanalyzer where it was
gettly taped into place around a plati 'um t'ermocouple folloIrg
improved packing prroecdures as outlined 'y Re-eau and Carlisle (1970)
wherein the clay sample was "sandwirchei" between asbehcos which had
been fired at 1000C a'd passed through a h"frr--,n ill fitted with a fine
screen. The sample holder c.ntal'ing the four clay samples with alter-
nating reference sample posiLions was then ccrnected to a transistorized
circutl oeTeremi nations were made at 25" sensitivity using a heating
rate of 10C pur minute fro:c r,'oro temperature approximatelyy 23t1 to
nfrred! soc-trc" rtr Aa sjs
!n'f i bn : o I.,aL i c b, c' y 1 n rin is *s investigat.d 'i th
1 10 -c i rho.o ar. es -sturatred .;s were
S'OC 1.5 erloi ulv'rized u irn an agae -ortar and pestle.
A m'xture consisting of 1.0 rj of the ground racnjs um-saturated clay
and aJpioxirmatiely 'lCO ng of spn:troscni c-grad KBr was used to form a
itr.nparent Fellet. The pellet was formed using a Reckman K ,r die.
Aproxiieately 200 ig of the KBr-clay mixture was placed in a Wig L -
Bug electric mortar and pestle (i,:ae by Crescent Dental Mfg. Co., 1839-
45 South Pul;ki Road, Chicage Z3, 111.) to reduce the particle size
and thoroughly disperse the sample in KBr. The optimum grinding time
appeared to be app.-oxiiately 20 scconids. The Beckman KBr die consisted
of an anvil and a ram constructed in -uch a manner that when pressed
together by a hydraulic press, the sample is compressed into a disc by
the confined space. A partial vacuum was created in this space by a
vacuum pump connected to a hose coupling on the die which led to the
aforementioned confined space. This tended to remove entrapped moisture
and air .-h;ch othernvi-c coull result in a cloudy to opaque pellet.
After cleaning all parts of the die with acetone, it was assembled
arid the 200 mg of Krr-clay mixture was transferred from the Wig L -
Bug mortar and pestle to the die. The assembly was then placed in a
hydraulic press and the vacuum pump activated. After 1 minute, slight
pr.assure was applied to the ram for 3 minutes. Hydraulic pressure was
then c.-ased to a reading of 8,CO0 psi and Iaintained for 5 to 10
:min utes. The vacuum was then released after which the hydraulic pressure
;as gradually released.
The pellet was removed with tweaze rs and placed in a Beck!ian
Infrared sample holder. It was then introduced to the infrared beam
'or an-l yis. The scan speed was 15 minutes from 4,000 to 350 c'1
The instru.eiL was calibrated by scannigr. a st'edard polystyrene film
from 4,000 to 350 cm-1. A KBr blank and Ward's halloysite No. 12 were
scanned as reference samples.
Sodium Fluoride Test for Allophane
Fieldes and Perrott (1966) indicated that large quantities of
hydroxyls were released when allophana was treated with NaF. The
magnitude of release was great relative to other soil constituents.
The aforementioned authors outlined certain modifications of this
knowledge which allowed a positive field and laboratory test for allo-
This procedure was used for field work in Colombia by placing a
small portion of soil on phenclphthalein paper and treating it with
I N laF. The appearance of red color was accepted as an indication of
an appreciable allophane content. In the laboratory, pH values were
obtained by suspending 1 g of soil in 50 ml of 1 N NaF solution. The
suspension was stirred constantly for two minutes after which a read-
;ng was Immediately taken on a pll meter. If pHi values were greater
than 9.4 after t,'o minutes, the sample was assumed to have an allophane
content equal to or greater than 60% of the colloidal cc.mplex.
Luna (1569b) pointed out, however, that this test has been found
to be positive for certain Colombian soils in the presence of apprecia-
ble ha!loysite 'nd aibbsite.
Sand ili nra-logy
Sand mineralcgy \,as determined for the 500 50 j) fraction sepa-
ra I ro- L: I Ii ey ic.l3
::sity u ing q .
1r, 1 1 i ,, roin. ,inre or
C p- t. > r I i u- ,t OIpa uC
in e c'?o of h-vy minerals.
'1 sis. Li jht J he vy ii i ra1s
I-o r,.i (s. g. 2.9)., /evy inernl
re i'cntifi i d wi Lh a 1 lari i ig
: /,;r,.] ,l :n i Irobenzri nc (n 1: I .552).
bi is of speci. s pr' 'ent in 100
miciner;' were abulat d epraritely
Mljor hor ions from profiles no. 1 through no. 6 wcrc: selected
for ricromorpholcgicil investigations,
V r i- ical y-ori '.ntod undisturbed peds iwere i; loved froim thie me tal
count i; her's use. in the tie ld and p lced in si.aldl 'luminu!i con l.t iners
approximately 4 ci: in dianimeer and 8 cm high i-d allowed to air-dry
for a few' days. Dry peds remaining in alumin um containers vecre then
placed in a vacuum -Iesiccator, An impregnation solution consisiingj of
a mixturee of 50% L .nirac r-esn /4116, 4: rronor-er'Tc sty-one, and 1%
Lupa sol DDM hardener (Pettry, 1969) w-'s th-n periodically introduced
to oacn contaiolLr ov'/ir a period of: 4 to h-ours unidJ- vacuum. Sialiies
erre then reinmved from the vacuum and Dpl-3:e. in an initially cold oven
.i,.] hated sloiwi to 10CC for approximat ly i2 hours. After cooling,
Lhe Alulminum ccnolainer ;as pecled off and the samip!es wire ready for
se5i,: on i nr .
Erypccdtisn of Thina Sec'ion
Thle initial step r;uas to bioc'k our a sect.ioi: 2.5 x 2.0 c.-t btwcen
0., to 1.2 cm thick using a Felker Di-Met, ,:odel 1i -R sna' i th a diamond
jlede and .'ter as a coolant. The slab obtained in this manner was
then lap-ground on ore side using aVon Hulen Thin Section Grinder.
This waas done in three steps, s arting with! coarse 150-mesh silicon
carbiJe on the rough grinding 1ip using Water as a lubricant. This
operation uas then followed by lap grinding on the inLter,-ediate lap
with 320-mesh silicon carbide. Final grinding was done on a 15 cm
agate lap with #1200 optical finishing powder. The last two operations
used kerosene as a lubricating agent.
The smoothly ground surface was then cemented to a 2.5 A 7.5 cm
petrographic slide using an epoxy cementing agent. The excess saeple
was then removed to a thickness of about 90 i above the glass slide.
This was accomplished using a specially constructed slide holder vhich
allowed a parallel cut to be made with the diamond saw. Further reduc-
tion of thickness rias obtained by intermediate grind with 320-mesh
abrasive on the cast iron lap. This process was continued until bire-
fringent colors of second order blue for highest orientation of quartz
and feldspar were obtained. This indicated a thickirss of about '60 J.
Final grinding was necessary to reduce the specimen to about 30 p in
thickness. This was done on the agace lap with #1200 aluminum oxide
optical finishing ponder. At the desired thickness, the highest bire-
fringent colors of quartz and feldspar were light yellow or w.hite. The
slide was then thoroughly /washed, and a cover glass was mounted over
the thin section with epoxy cement (n = 1.58).
Thin section slides were described using a petrographic microscope.
Photo icrographs were obtained wiith a 35 rnin camera attached to the
microscope. Thin section descriptions were made using the terminology
of Bre'..er (IS64).
S .i,'lI '- 1 i STUiY A FA
ILo ; ion
Thli Cap r e- nto of ik -rilo is o3 cated in th' c txtre:,e soi.ithl.,as torn
pFr of Cole rbi S< uth Arci ica (Fig. 2). Nari o is bourdd o1 t-he
ror:-h by t'e Dep5 rtla ,lo of Cauca, the Pacific Ocean on the ,,est, the
DeplrL't. ,,L o of Putom;yo on the east and Ecuador on ith south, it has
iian -r of 32,70' km2 (Banco de la Repub ica, 1959) and !ies fro: less
than I to slightly more than 20 nori' of the equator.
rE si/ cg'PJ.
Miari o is ch1 aci eri ze b by .levationsi ragi ng fror.i sea 1 vel a lng
its Pacific Ocen lshol%' i nei to n miaxili m of 1,830 im at the snow covered
su. ,. t of volcanoo Cil bc!. near Tu;iIerres i tih' Andean uplands. The
teinnina! ranges o: the Ai;ne dividai' in the northern part of Narir.o i -
to th.re distinct t chains called "cordill!eras" rd extend almost i the
At!ntic Oce in (or iC'riihbcn Sea). This junction imparts a very ruggd,
mountainouss characLtr to the castin part of Lhe departamc.]to. The
An <'. n -i fhli hands .-r co ns i tu d by i tera!ti it y i toLrmontai e *,al ieys
and ridges. Probably the most striking feature of the uplands is the
--b.nldanc of volcenoe., alasco (I1;6) reported that 2, volcarces habe
Le. iJ '.ti fied in iNar;7o of which 5 are knov.n to be active (Cumbai,
Ch! l-s, G;]a res Az:ifral ~nd Dona Juara).
nt.i;::i;nLarne sirs of cons de'rable exCent iccur frequently in
COLO i BI A
Fig. 2.--Coiombia, South America, shoving location of
the Departanento of Nari- o.
ha 1 s v. t h
T-.pic-l of C- is a ]Iar I1' e r Tlque-rres
c;iy it i)lf la r. ea .r i.,c vao'o. ,rl (Chiles,
Az r'o j l) rF r 'I e w s -frn p ripl.i y,, of the Anres. ThIu
is 1ppo 'i; tely 3,000 m in at i Ltd and is occ(ujpid by
S fi t .strii. A 'i M i er ba sin eJi ts east of Volc.:no
U ti tuJ3 of 2,530 inm
st,.?r part of Narino is co-priscd of Andean piedmont foot-
;.rg ra her rapidly into the Pacific coastal plain,
Be rock and Surficial Geology
Lana (lSjna) indicated that Andean basement rock composition in
Narino cwas primarily andesite, basalt, and tuff of the Cenozoic.
V.rcla (1933) concluded that recent eruptive rocks due to volcanic
activi ty of the Cenozoic domindtrd a rmljo part of Nlarino.
Luna (i969a) stated that volcanism tu.dides and pyroclastic nmatrial
inventories wver quite limited in Colcnobia. He reported that rost
references were Lo soccific OruplionS .,iLn insubstantial details on
quantity and comrpsition of pyroclastic materialss A maximum age of
7,000 years by C 1 has been reported for an ash 1dposit in .he Departa-
mento of Toi ma.
lEipirical observaLions by the author in the Nariino area revealed
that the highJ! -n' have teen universally affected by aeolian and fluvial
l' rocl asti deposit ts; t'ocever, the influence of this factor on soi I
ldevelcpi.ment varied considerably in magnitude. volcanic ash 'ccumula-
tion ar:d di; tribhion in the Nari-o highlands has been r mandifested as a
'"p ch.:orl'" or discontinuous p.tern over the laodscape. S-:vecal basic
fcL:.rs hia. pro:'ab!l contributed to this pattern, De to .iic strongly/
dissected nature of the region,considerable ash has been eroded from
the steeper slopes. Differential deposition due to a-berant int r-
,ontane wind pattLrns has, u-doubtedly, been a supplsnaintal factor.
Additionally, it was very difficult to assess the territorial limit of
various ash deposits. Wrinh) (1964) indicated t'at mapping of ash-
derived soils is a probleri in peripheral areas at the ou:er territorial
confines of ash-mantled landscapes. Figure 3 shows the general distri -
bution of volcanic ash deposits associated with Volcano Galeras in
addition to locations of profiles 1-6.
Areas in the Mari-o higniands \rhich ;ere covered by thick ash
deposits characteristically exhibited smooth, rounded land f orm. which
generally conformed to pre-e"i tin surface configurations.
Nature of the pyroclastic deposits changed considerably from
northeast to southv.-est in the highlands. Deposits in the Pasto-C'.:-saco
region (Fig. 2) were composed of finely corTiinuted ardesitic ash ex-
hibiting little or no stratification. The character of these duposits
indicated gradual accretion of ash where eruptions were infrequent and
not of great magnitude. The contesting nature of pyrcclastic deposits
in tne Tuquerres Ipiales region (Fig. 2) was r,.anifested in stratified
beds of ash and lapilli. Lapillitic strata ,.era quite often pumiceous
Thick wall-stratified and well-sorted fluviatile pumice beds were
observed '!ong the western walls of the previously mentioned Tuquerres
basin. Similar pumice beds were observed along drainage outlets to-
wards the Pacific lowlands and I k- north of the Ecuadorian border
S Salers ,
Oio-8 :ii j OF nIlAn'i,1 SLIBla
S-in 21 0 ci
dl?:itU (m ml
Fig, 3.--Cross-section of !ari n Colombia study -ea showing locations
of profiles I-6 relative to Volcano Caleras. Stippled araas
sho5: ;U >ei;zed disLribution of volcanic ash.
Fig. 4.--Pumice beds I km north of
S i ty oi i c i i o I p r ,, .ri o
t .'c. x::s" a ri l e rath r i i .i
,"J/0 I! oi s of !o!lcano tl rnIsi i stc red 0n n I r .j o annual
precipita lon of 700 n'm and a a verae te Q era tJr'; of 131 At the
lotonai -gricll Iur l station (2,/50 m), thl e i ver e annual rainf ia l and
.tmp-ratuce .,re 781 mm and 13C, respectively. A station near Consaca
(1 40 rim) in :he subtropical zone had an average annual precipitation
of 1,9,2 mn and temperature of 20C. Tumaco, on the Pacific coast,
reported 2,819 nm of rainfall per year and 26C annual temperature,
The co;,,lcx topography and wide altitudinal range of Narino
i.,p rt considierble variety to local climatic conditions. Pro;xi i y
:o i-e lqunor, however, dictates an isothermic temperature rcegi,-a
which is c!os-lyc related to elevation. Luna (1969a) stated thar. oi--
plarature is related to elevation in Colombia by a 6C dccrase for each
i ,CG m i ncr ,c-s, in altitude. Espinai and Montenegro (19e2) re?.o.' zed
five i3,ajor la-inperai:ure zones in Narino based on the aforel-'n tionc
Ther..l *riadient (Table 1). These zones ranged ''oil t;op;cil (> 2-C)
in ie FU r c fc lovlarids to sub-ioipine (3-SC) in t:-e Ar'-daln highlands.
lti tlin each tleriail region, subdivisions w re r ade on t'>c; basis of
p-ci pi :t tion di lfcrcr;cs. Precipitation is maxi,tus.i alorg sIopes F. .'i n9
;ie Pac;iic io',-lanids a.d tend. to decrease It th depch in i ite&:-. Laie
v!illeys. Varele (G93) reported a disi.;'ct drc/ s aon occutri rg; during
jl.iy, August, a-id Septeriter in the Pasto-fio 1:y1, s- :ior oF N.-roi 'I .
Table Cl i mate-vegeta 'on rel ci onsii ps in Do rt
Colo bia (Espina! and iontoneg'aro, 1352)
500 -- 2,000
9 SA 3,500 +
500 !,000 hf M
1,000 2,000 vhf M
> 2,000 pf M
500 1,000 df L'
1,000 2,000 hf LI
2,000 4,000 vhf LI
>4,000 pf LI
500 1,000 df S1
1,000 2,000 hf S1
2,000 4,000 vhf S1
> 4,000 pf S1
T 3 800
= grassland ("paramo")
= pluvial Forest
= very humid forest
= humid forest
= dry forest
= very Jry forest
SA = sub-alpine
M = montane
LM = lower montane
ST = sub-tropical
T = tropical
Rai nfa l I (mli) V g La i on A I ti _uiue (m)
i na| I i' ro (1962) us th s of .yo l ;, (;-I)
ipr Ci i ". C r c vir ft 'i'o i n C )cb i I.
U 1vill ia3 i/ i C 1 c uI C isp i ioa1 trr r ll-
So";h ,:., y i dd" i ;d 23 differ,
indi nons s io OD-prt i .onto Nri no (Table I). The Nlriro st,dy area
-rcom ,ssad 5 majorr v2jetation formations rangiiig from dry sub-tropical
forest to sub- pinr grassland. These pertinent formations ire discussed
below as outliin a by Espinal and Montenegro (1962).
ry: yLTripi ca I Forest
This Formition is found predominantly in intermontane valle-s and
is characterized by 18-24C annual temperature and 500 1,000 nmm annual
precipitation. Rainfall deficiency in these valleys is most likely due
to orographic effects which produce aberrant local wind patterns. The
inajor part of this formation occurs in mountainous terrain with roderate
to very steep slopes. The original vegetation has been almost eitt:rely
altered by man. The lone Narino plant species list published by Espinal
and :iontenrgro (1962) was enumerated in the Guaitara river valley for
this formation. They reported that the area uas covered with dense
clusters of a trce ca led Cocaa' (E rthroxylon sp.) associatLc with:
Crtoln. fr-l~ ie.s H.B.K,. (nosquero),
fa .a- 23:cl t, ? (tacishuo) ,
C~li and, a sp, (carbonero),
A clj.a f n--si t i l id. (pe ),
a." na- c lese s H.B.K, (vrenturosa),
lporbi a cj-aaca:eni 8Sos (Ichero),
antisa sp. (tuna) ,
C-'' lo_ reu. sp. ( c e i on),
TJ.c3P_, FJuss. (chi r lobi rlo),
aursra tc., -eiceca Fr. aed !1. t i arraco ,
-C_ s-l i L:ts : (ti ntilla), and
Ve rbenaceae (pendo).
In Nari o, areas of dry sub-tropicai forest are used for the
cultivation of coffee, suigr cane, plantain, a,:d in sore cases exiensi c
grasslands for cattle production.
Drr' Lower Montane Forest
In gener al this vegetation Formation has as climatic linl- s an
annual temperature between 12C to 18C and annual rainfall bt!e-en 500 mm
and 1,000 mm. Dry lower montane forests are generally encounteiud be-
tween altitudes of 2,000 m and 3,000 m in interimontane valleys and
basins of the Andes. The primary vegetation of this formation has been
completely altered and destroyed by man. Due probably to an ideal
climate, indigenous pre-Colombians populated a large part of these
areas. In establishing their agricultural systems they initiated the
demise of the natural plant communities of this ecosystem. Areas which
are left uncultivated are invaded by grasses and small trees or i!hrubs
such as Cordia sp.
Some common species identified in this formation are as follows:
Solanium maria natum,
Euhor bia orbiculata,
S particum jsceum,
Phyl lanthus salviaefoliu s HB.K.,
Croton sp., and
Large tracts of this formation have been reforested with eucalyptus
(Eucalyptus lobhuus) and pi-. (Pinus radiate). This vegetation forma-
tion has traditioeall, supported a high population concentration in
the Andean highlands. Ory lower Ircntane forest alees are considered
to be some of the mosi productive regions in the country. Within these
areas are located large cattle ranches and commercial forests. Intcn-
si v, c iuc ti' of v 'at, corn, pott tes, and tree frui ts is -ncouiraced
in io /-G I r irrigation systems.
MI 1n t o' r o n r Fi, ost
I is v g,!t tioni fo irmation is of I ir i ted occirr'r ic in Col .' bi' .
fhe r,:'-ratur r hiJ al i tude raJge in this 'orma ion is sirii'ar to
that of the dry lover i,:ontane forest system; however, avcragq: annual
rainfall is higher ranging between 1,000 mm and 2,000 rim. Cliniat is
generally mild with gentle rains occurring throughout the year,
Occasional frosts occur at the higher elevations of this formation.
These forest formations occur on undulating to moderately steep moun-
tain slopes and intermontane valleys and basins.
In areas where the population has been established for several
centuries the natural vegetation has been considerably altered.
Some common species identified in this formation are as follo'-s:
< Crcus sp.,
Ced re I a
eLin^annia sp. ,
In areas here the topography is flat to undulating, crops such
as potatoes are grown. IMore strongly sloping areas have generally been
esabli sherd as pastures composed mostly of kikuyu grass (Pennisetum
rlanderstinu) Pine and eucalyptus reforestation has occurred in many
miarginal agricultural areas.
iumid io!itarle Forus t
This formation occurs generally between elevations of 3,000 m and
3,500 m in the Andes although locally it ,ay extend in sowe cases up
to 4,00) m. It has been referred to as "sub-para ,o" by natives. The
Tuquerres basin in Harino is corposed almost entirely of this vegetative
formation. Average temperature generally fills between 9C and 120.
Precipi Lation ranges betv een 500 r" and 1,000 mm annually. Even though
rainfall is relatively low, the climate is quite humid due to low
thermal efficiency that is associated with considerable cloud cover
and high altitudes. This is reflected in low evapotranspiration rates.
Day temperatures are generally quite cool and nights are frequently
below OC with common frost and ice formation.
Humid montane forests occur on varied topography in the Andean
highlands. Considerable areas of the formation have been sacrificed to
cultivation;howeverremnant trees and on occasion complete con',unity
remnants have remained intact. A partial species list of a humid
montane forest community in the Departmento of Boyaca is presented as
Wei nmannia sp.,
Polylepi s p.,
,e ;ari s sp.,
Bona rea sp.,
Espletiva sp., and
Mi conia sp.
Population density is not great at this altitude althc9gh the
soils in tnis formation are quite fertile and have sustained cultiva-
tion for many years. Potatoes, wheat, barley, and vegetables are grown
on the flat and undulating areas while the sloping regions are generally
utilized for pasture.
01 *'1"t.i~ P cu pios th, hi
I;' t .-n l i S I i is :not axt
c- tur l i ,3or :c Col','biaJ st'
s iici ily ,id h e to th ir i
cl i i to. R i, iif i :y ranqe froS r 5i
an n al t~'nper-l t iur bet:,v.c n 3C a dd 9(
St!3cs., especially F stuca and C_1I
~ad shi ubs (Fig. 5) such as:
Di.plo t.ejhi u revolutum Blake,
S ciioa s ccinioides,
V -l rimn s arborea,
icL-i i a buxi folia,
P Jiyl/eji_s acea is,
S. .- sp. and
gl st ?.l.vo,! , s in -he Ai dl s bef} ;
ensive and is of very little ijrl--
b-alpine ecosyste-s have i:':n in-
nacce ss) ility I-rd iniospl : bi
00 mm to 2,000 : jn annual ly with an
C. The veoytation is dominatO d by
Ingrostis, interspersed vwtth bushes
Fig. 5.--Typical vegetation of sub-alpine
grassland near profile 6. Broad
leaf plants are Esp el i sp.
REFs., fS A ) DISCUSSION
ro nic Mlatter 0 Oxidi tion
Lavkulich and iens (13/0) p esented datia ccarli-y howing that
not only was NcOCI r.ore efficient in oxidizing organic matter !but ihat
the content of Si, Mn, Fe, and Al in extracts after treatments was
signi f'ic-ntly higher for H2 2. Comparative data for selected Andosol
horizons using H202 and NaOCI treatments (Table 2) were even more
driaaatic than those presented by Lavkulich and Wiens. H202 removed
five to ten times the amount of Si and ten to seventy times the r.:ount
of Al than that removed by NaOCl. The H202 treatment was the sarm as
th t reported as H202 I by Lavkulich and Wiens (1970).
NaCCl would appear to be less destructive of sesquioxides, silica
coatings, allophane, and crystalline clay minerals. It can be con-
cluded from these data that NaOCI was a more acceptable reagent than
H,20 for rapid routine organic matter destruction in Colombian Andocols
prior to nineralogical analyses.
lsPersc ion of Andosnl ClIs
iL would be aiJvan : jt us at this poinE Lo cx;
d;spersion properties of soi Is conai ning high qlluai i te s of al ophane.
Ai thoughh Lhe intent of this tiudy was not: ie thlod oriented, an interest-
irg point has a risen. -iistori ; iIy most soil mini erc logy analyses have
been performed on air-dry samples. As has been mentioned previously,
Table 2. Fe, Sioand Al amounts in ettrarts after :r: ant of certain
Andosol horizons by IaOCI or H202
Profile ?1o. Horizon Fe Si Al Fe Si A
Sppm -- -
3 A12 2 240 0 0.2 902 88
2 240 10 0 1,001 99
5 Al 5 230 30 36 1,738 1,705
6 270 30 35 1,914 1,760
5 AC 6 390 30 117 2,500 2,079
6 360 30 118 2,519 2,211
6 Al 64 330 170 164 4,025 6,105
73 350 220 116 3,630 5,830
h, nh-e "'-n enc cs in AnJoloi cly dispr'sicn due to ir-
Ir-....i c t. It is :, p l it 'i riors iive hocn
J reki nj-p th3 r s. A yriad of toch-
ni.,; J 1-'v b):?iL :i, l, ; th c; xyin3'x g o. O success (or faii Irc).
Ni'y e L ase .:iho
Dii i 1 i r .oc1 r c ac i J (see, for ex- pl e, 3irrell I : Fi eles, 1952)
his been used by cmr,/ workers Fields (1955) and Fieldes aind Taylor
(1361) dispersed Andosols, wi th varying success, by adjusting the pH
to 10.5 with H.1-. Kobo and Oba (1965) used a sonic vibration method
for disintegrating aggregates to facilitate mechanical analysis of
volcanic ash soils. They reported that in most cases the clay was well
dispersed by Calgon after sonic treatment but addition of dilute HCI was
still necessary for subsoils dominated by allophane.
In most cases mentioned above, dispersion was obtained by some-
w.t'hli drastic treatments with little consideration for allophane. Ahmad
and Prashad (1970) until recently had been impeded in their investiga-
tions of Andosols of the West Indies because they found it impossible
to disperse these soils even by the aforementioned "conventional"
methods. They discovered that zirconium nitrate (Zr(N03)4 5 51120)
solutions were very efficient soil dispersing agents, especially for
Andosols. They postulated that the high ionic charge, small atomic
radius, and low ionization potential of Zr apparently resulted in
saturation of the exchange sites and some tetrahedral substitution for
Al leading to a net positive charge on the exchange complex. Achmad and
'rashad felt that their data were the most reiiaBile so far quoted for
tnese soils. Unfortunately, zirconiume nitrate does not lend itself to
use ;s a dispersing ;cgent in mi rer.a og;cal i nvestig atios, Due most
i kely to its o', ioniza tion potential, it focis prec;pi tacc~ with most
of the accessory solutions such as i;gOc, r.qCl2, and acetone which are
used for satiratfon and washing of cl-e colloidal complex in cly miir r-
It was observed by the author that seemingly good production of
clay (i.e. good dispersion) jas obtained front surface horizons using
NaOCI and from field moist subsurface horizons using 7i Na2CO Zir-
conium nitrate also seemed to provide adequate dispersion so it was
decided to verify qualitative observations using zirconium nitrate as
the best available standard. Sample dispersion with zirconium nitrate
was according to the method utilized by Ahmad and Prashad (1970).
Samples were centrifuged, clay decanted, flocculated accordingg to
Whittig, 1965), and weighed. Silt was separated from sand by wet
sieving through a 300-mesh screen and each separate was weighed. Data
in Tablc 3 clearly indicate that in most cases there was no striking
difference between dispersive quality of zirconium nitrate and either
NaCCl or Na2CO In 50% of the cases zirconium nitrate gave slightly
better clay production. Seventy-five percent of the time zirconium
nitrate dispersed samples, in which organic matter was removed by
11202, gave slightly better clay production than NaOCl. Three out of
the four horizons dispersed with Na2CO3 produced better than zirconiun
So it would appear that for Andosols of the humid subtropical to
sub-alpine uplands of southern Colombia the maintenance of field-mcist
condition assured adequate dispersion. it also sceeis that even though
thesee soils contain high quantities of allophane the principle of sodium
saturation of the exchange complex cad resultant development of strong
electrical repulsion forces remain valid.
Th,)ble 3. i'f, t: f trit Ln ad, disi s in t i Li cl s i /.e
I i : ic
Oi Dv i por-
Rrij 1 .,.ov l s i on
C-- 2 All H202 a
C-2 2 A 2 H202 a
C-3 2 A3 H202 a
C-4 2 [B] a
C-5 2 C a
C-15 3 C a
C-l7 5 AC H202 a
C-34 4 C a
- Organic matter removal unnecessary.
a Zirconium nitrate,
b Sodium hypochlorite.
c Sodium carbonate.
Pro i o
Lab, o. ;o.
Sind Silt Clay
39 '3 32
38 28 34
40 30 30
39 34 27
34 39 27
31 L6 23
37 40 23
35 39 26
29 42 29
29 40 3i
22 40 38
24 46 30
39 34 27
33 41 26
25 48 27
22 48 30
Detai led field descriptions for the 10 oil- elecued in this in-
vestigation are presented in Appendix Table 8. The discLs' on of
morphological and subsequent data wil relate initially to p-ofi ls 1-
which we're selected in an altitudinal sequence between 2,000 and
3,510 m. Profiles 7-10 will be treated individually as ancillary sites
providing additional pedogenetic information.
All soils were well drained and quite permeable. The altitudinal
sequence of profiles 1-6 exhibited definite morphological trends with
decreasing temperature. Horizon sequence at low and middle altitudes
(2,000 3,000 m) was AEB] C; however, above 3,000 m the carbic sub-
surface horizon was absent imparting an AC sequence to these soils.
Surface (A) horizon thickness tended to increase with increasing alti-
tude. Surface color was dark grayish-brown (IOYR 3/2) in profile 1,
but all subsequent surface horizons at greater elevations were black
(IOYR 2/1). The [B] horizon thickness tended to decrease with elevation
and was replaced by an AC transitional horizon in profile 5 (3,120 m).
Cambic horizon colors displayed maximum development (7.5YR 4/4) at
2,000 m. The EB] horizon color at 2,150 m (profile 2) was yellowish-
brown (I0YR 5/S);and with decreasing temperature,both value and chroma
of this horizon tended to decrease. The C horizon colors tended to
have similar hue and value but slightly lower chroma than the overlying
 horizon. Str.ucture or A horizons tended to be subcng'-lar blocky
IBrackets F] are used to indicate a caenb;c diagnostic subsurface
horizon. Right (i164) advocated the ses of this symbool in describing
hb lo. 2,,U') i o I C. ul 1a ib ,v'- is I vatioi. C..,1 bic pr I horizon
S ; s ,are 1- ,'.i < blo y. a joriity of the soils, C
he I r1 r, c I s si ve zxce t at l Ow r a 1 tii tu the e,
.a o jLcrncy s.o r-s the lsl ian ular blo k 1 y typn. Notable .was thc
1.'k o i i-. t d clay iargill n -) on p-"1 urfce's. Oro nic coltin. i s
, a cor aily :otad on individual sand grain surfaces in A ior ;iois of
ill soils (Figures 6 and 7).
Pr of l 7 u3s a shallow Andosoi at 2,000 m in eIevation. The A
horizon was unusually dark (IOYR 2/1) for similar soils (i.e. piofi le I).
Profi le 8 was sampled and described in an alluvio--lacustrine region.
It appeared to be a young, well drained soil and showed little evidence
of profile development. The most striking feature of this profile was
a layer of white (IOYR 8/1) silt at 131 cm. It is possible that this
Iayer represented relatively unweathered fluvial volcanic ash deposits.
There was a pronounced change in depositional history below 152 cn.
Profile 9 had a thick (66 cm) black granular to blocky Al horizon.
Colors of the C horizon were redder in hue (5YR and 7.5YR) then was
typical for Andosols at comparable depths in the study area. The C2
horizon was probably developed from andesite. Although morphologically
similar to Andosols this profile exhibited negative NaF test results
for all ho,-izons. Profile 10 was similar to profile 9 but it was more
strongly dIveloped. The A horizon thickness was less (39 cm) and not
's dark (10YR 3/2). It was the only profile with an argi llc horizon.
Although aeolian pyroclastic materials have undoubtedly influenced Lhe
pedogenesis or this soil it has developed predominantly in andesitic
residuum. According to Wright (1964) the thick dark A horizons ex-
hibited by these soils have sone connection wi ih primi tive iwes.lesring
Profi l 4
1-4 repre-enting a i i i tu-..na
P.-ofi le 3
Fio. 5--Co1or photographs of profiles
sequence of 2,C00 2,730 m.
le 5 ir 6
Frof i le 8 rufi ~e 9
F;'. 7,--Coior photographs of prcfili s 5 ard 6 reprcsrniin al tit ud i al
sequence o- 3,120 3,510 -. ad cirillary profiles 8 and 9
at 3,020 and 3,06.' Im.
products of volcanic glass. T- :' ,o Andcsol A Iorizons r~~: prol'- ly
zhe result of organo-metallic (.n"i,p;- nic) complexes encouraged by
occasional uniform depositions cf fresh volcanic ash. Increasing thick-
ness of A horizons with altitude was probably due to decreasing bio-
logical and/or oxidative decomposition due to decrease in temperature.
Proximity to volcanic ash source was most likely an additional thick-
Genesis of the [B] horizons was somewhat more difficult to ascertain.
The soils are quite permeable but in their natural state do not have
well developed ped faces. Due to relatively uniform rainfall the soils
appear to remain moist throughout the year. Year-round moist condition
is encouraged also by high water retention capacities. These factors
tend to discourage desiccation fractures. Lack of layer-lattice sili-
cates whose plate-like morphology expedites orientation on available
surfaces is an additional feature contributing to the lack of B horizon
Overall development of profiles 1-6 seems to have been highly
temperature-dependent. Decreasing potential evapotranspiration with
increasing altitude may have discouraged profile development at higher
Soil pH measurements in water and I i KCI solution are recorded in
Table 4 with the exception that neutral salt pH determinations were
not made for profiles 9 end 10, In all horizons ji' profiles 1- p:
values we.re hihber when .e-3sur-,d in afterr -tan wen .casured ;n 1 '
-1 ~ ~ ~ C 00' -to c 3u7Cr-mi~
O . .
-n Ln oD o o~
ccr 00cc cc\ .
-0 o- -t mt um-T
Ln i: LA tr ii Ln A
.-4 0 -- -r- io r
cr. L1j **^ (
0 0 r- o r--- m- n
\ o i'^o r,% d.o ur r0-- c -> -.J t n
-o o o o 00 00
o -: TNN -T -- -Ct(
'.o. ml i, .- .
S oo. ooo0 o o oom o
S'4- 00 0 '- 00000 4- 0000
_4zr ooocc- o-o-
rocin- occccoM oooo
cco 4O 00-0- 00-0
1 CILi. 04.o C Lc.0CO 041 O 0 m oo. -0
0 0 d0 -cOdd --0 4 -O0dd
o -- . . 0 . . | . .
--o....... 4 i 0 -00-
.j- o0 <0-0' -0 c.- o0 o -- ,4 ', o r--. io
SAdd-000 -0000 4 000
un. )O i0)00 .- -t 0)-N
0 43 0 -- N
10 ^fjo40) ~t -0J0
0 cI U 0000 '1 00000 . 0 000
S -oo00 00000 0 000
I. I. . .1 m .
o -N20 )0 N 040) 0)00)
u0 I .m . 4 . .
_i> I r 0)0)040 0)0 0 -
01 04N1 -41 O --1.
S100 1 1 1 1 -s
~ ~ ~ ) \ m -j- h-c o oc r-- ~ l\ r~c
Or -'. '.-' t-j- N CO -'i
0--- 1 o r N- -. rr, r^, r- r- N o o r-.,o
0 o Ln --OO N 6-- 0 c0
CNI >0 0 -Zrr N N -^-^- m*2ccONo(
S,0 co- r --o ,io -co -. o-l
ooo Q.I -c-N- c o\o
II 0-0 0000 0010
ou I, . .-0 .N. . .
IU) --t o -20020 0 '.l G '.0~Nr'
S0 N N
I I' 4 o o -
(0- N- Nfl2 r- *- (N --Nt20
0 Ie '- 000 C- 0000 IIo 00000
S-Nt 021N- r02 N-.Z-Nrc
Ic --N2 cm- O\cOc
-U -- 204) u\ oco-4 -
4- --(Ni--C- --<<<-2
' O~-- ~ C I- << << <- ce ^U O
(-1 0 -
a, Lo 00
N-2dL 0 Oh-3
-0 L -- o a-
uo o o
- N (N c1
, 00 ao 00
0 IO i 0 0 n
-,l iti n. C li isl- (I. ) ,' ,- r i 'nlt neutral ,t pH 'i,. l s ir..present
i i ty in !i ) sdil d t:' ,fore l,:uld l a ,jctel .o in 'lr.
il rI fiction values v.re r c iar, ab ly uni forn for profit les f-6 with
j i' of 01 5.1 to 6.0 in wai er and 4.2 to 5.3 in KCI. Even Lhough tle
i-; i i:deJ of vnriabi li ty hardly cnconipised one pH uni t, certain trends
or, ti noticeable. The pH values tended to increase with depth in tl-.u
ploFile and to decrease with increasing altitude.
r i':i c Carbon
Organic matter is formed in the biological decomposition of plant
ard anlial residues. Narifio Andosols had unusually high organic carbon
conients as shown in Table 4. Organic carbon contents of Al horizons
of profiles 1-6 ranged from a low of 2.9% at 2,000 m to a maximum of
oq.L in profile 3 at 2,440 m. Values tended to decrease with depth and
to increase for comparable depths below the Al horizon with increasing
Profile 7 exhibited lowest relative organic carbon contents of all
profiles investigated. Profiles 8-10 had similar A horizon organic
carbon contents;however,for profile 8 these values remained relatively
hish with depth.
.Lha eable Bases
Eci lr.neable calcium values geqera i' decre e -ed .ith depth in the
pronfil and ,i th increasing altitude for comparable depths in pilfi es
:-b. Treirds .e re mr're variable for profiles 7--0, i'xcha geable Ca in-
cri',:?Sd wirh depth for profi l-s ard 8; remained reF!mii-ely constant
For prcfile 9; and cec ea-.ed with Idepth to rch C horizonn for profile 10.
Corn isLent tr-ends '.re ;. l di -o avrd hy r chc 'y-,o abI e M s. dist,'ibu; tioas
(Table 4) for pio, iles 1-6. M.axium exchangeable Mg ..as encountered
in profile 1 (?.,COO m). Exchargeable leMg increased with depth in
profile 7 but decreased with depth in profile 8 where maximum values
(6,1 9.1 meq/100 g) for all profit les investigated were encouniteed.
Exchangeable Mg values were variable with depth in profiles 9 and 10.
With the exception of profile 3 exchangeable K contents tended to
decrease with depth for profiles 1-6. There was a general tendency for
exchangeable K to decrease with increasing elevation for these profiles.
Maximum exchangeable K contents for all profiles investigated occurred
in profiles 8-10.
Exchangeable Na tended to decrease with increasing altitude for
profiles 1-6. No noticeable trends were observed within individual
profiles. There was some tendency for exchangeable Na to increase
with depth in profiles 7-10.
With the exception of profile 3 total exchangeable bases for
profiles 1-6 tended to decrease with depth in the profi le;although in
some cases such as profiles 2 and 5,there was a slight increase in sub-
surface horizons. Total bases increased with depth in profile 7 and
were maximum for all profiles investigated in profile 8, Total ex-
changeable base contents of profiles 9 and 10 were similar in magnitude
to those of profile I.
Exchangeable aluminin values for profile 1-6 tended to increase
wi th increasing elevation and decrease with profile delth again wi th
the exception of profile 3 Exchangeable Al distribution was erratic
with depth in pr-oaile 7. Profiles 8 and 9 were quite le: in exchange-
able Al in comparison to all other profiles investigated. Profile 10
Si, i it d a r in fch Ie
r: r Ci' C??'iLy.
CI ion change cpaci ty vailucs w,;re va-ri l'e and did ot display
ti ..! i h profile depth or altitude. Profiles 7-10 did h1ive slightly
io.:r C vC values than those exhibited by profiles 1-6. CI.C values
-a.-ged from a low of 14.9 meq/100 g in a buried C horizon of profile
6 to a raximun of 65.7 meq/100 g in the Al horizon of profile 2.
Fr c.e 1ron Oxides
Free iron oxides tended to increase with depth in all profiles
and generally decreased with increasing altitude for profiles 1-6.
rMximum percent Fe203 for profile 10 coincided with the B2t horizon.
todinjiu Fluoride Test for Allophane
Sodium fluoride reaction values in Table 4 indicate that all
horizons of profiles 1-6 were dominated by allophane as evidenced hy
values greater than pH 9.4. These values ranged from the minimum of
p! 9,.4 in the Al and [Bjhorizons of profile I to a maximum of p'l 11.4
in the Al horizon of profile 3,
lanetic J nterre-ati;onlshsps of Chemical Preperties
The aik of picfi ;e development and disti'ibution with d
::-st chemical p rca.,.-ters indicate t',it profi les 1-6 were ycuihul
soils. The A horizGins of thesee s.ils -Aith their cark colors due to
high organic carbon contents provided visible evidence of profile cif-
ferntiuation. Acc!u:;ulation uf -:rganic carbon especially in the surface
horizons of profiles I-6 was most litcy encouraged by a high amount
ani of 1,.43 i: q/./100n n in n J
of biologic a i cc,'i ty and the presence of hi ghly rea' ,.i ve i a- 1 ic
-'rfaices in rth firn of allop:rns and oiher ar.orphous col lics. Tii
relative. ly Ic;' org ,!-ic carbon content of the Al horizon of prof!l I
:.is due mainly to t'e oxidation enhancement of hig'-er temp ie ure-s.
SOganic collo;d translocation was noted as evidenced by the rei Lively
high ioranic carbon contents in lower horizons.
Base saturation and pH values were generally unrelated for profiles
1-7. Interpretation of CEC and base saturation data was confounded by
the presence of allophane which has a highly pH-dependent exchange
capacity. Cation exchange capacities for these soils were determined
r;: h i-14HOAc at pH 7.0 and consequently were high due to the inclusion
of a considerable amount of variable charge. Cation exchange capacities
deaLrmined at lower pH's or at the prevailing field pH of the soil
generally give a more realistic picture of the actual charge participiat-
i:n in exchange reactions under natural conditions. The magnitude of
permanent charge would be expected to vary according to the degree of
tetrahedral substitution of aluminum for silica. The amount and crysi.-
aliin:ty of allophane present in addition to the presence of crystalline
colloid.- species with low pH dependent charges would considerably
influence cation exchange capacity measucremnts /t pH /,0. As wiold
be expected chi aforementioned factors vary from horizon to horizon
and fro., soil to soil. Co.-squeijntly base saturat:on value h-ve dubious
inter.prc active -orth Ju to a changing cation exchange capacity base.
Tfie cnt;-ibutioi of organic matter, especially in surface hori,.rs, to
confounding ilterpietation of these data cannot be ignored.
The distribution of free i on oxides with profile depth indicates
that Fa has bean relea. d from primary minerals and cranslocatcd by
percolatinig wat-r to lcwer horizons. Choluviation has most likely leen
r o, .e ri :, ech-i s of ir.n trr n oc i n in dd'Jition to
r-djctio" ,nd sub a jent lnecdhi .
/I lepha.t ccn n;i; as slo;n by N-iF Le t pH vai.s wer, "eater
at :.isher altitides for profi.es 1-6. The tendency for th':e values
to decrease with depth in the profile indicates that allcphane has
taken.on a more crystalline character and/or there has been an increase
in crystalline phyllosilicates. Either factor or the combination of
both i.p1lies a dccrc3sed capacity to release hydroxyls upon treatment
with sodium flucride solution.
Particle size distrib-'tion data for profiles 1-10 are presented in
Table 5. Several horizons in profiles 2, 3, 5, 6, and 7 refused to
disperse in sodium hexraetaphosphate. The. A12 and A3 horizons of
profile 2 and the AC horizon of profile 5 were dispersed with NaOCl.
The [B] and C horizons of profile 2 and the C horizon of profile 3 were
dispersed with N2CCO Clay distributions with depth for profiles 1-9
indicate no evidence of downward movement and accumauation in lower
horizons. A maximum of 483 clay (<2 p) was noted for the BI horizon
of profile 10 which did not coincide with the argiilic horizon as
determined in the f'led. Fine clay (< 0.2 ;j) conrtints are irosi likely
greater in the B2t horizon d';e to maximum deve!opiisnt of clay skins
(argillans) in this horizon. ii ller (1965) reported that the major
potion cf argillans in a Canif;id silt 3lan were composed of < 0.2 i
clay. This conclusion was confirmed by Caii-o''n (i68) on similar soils
in northeastern Ohio.
Tale 5. Phy ical properties of s lce, d Colt -ian soils
P, r ticl SiU a D;s : ut bu 1o;I
Sand Silt Ciay
2 .05 .05 .002 <.002 15-bar 3uik
Horizon Depth ------------- ,"-------------- H20 -osi iy
Al 0-45 27
 45-73 37
CI 73-121 25
C2 121-151 59
C3 151+ 15
All 0-41 45
A12 41-58 39
A3 59-70 31
Le] 70-96 35
C 96-160 29
All 0-50 *
C 1201 27
Al 0-68 29
A3 68-88 28
183 83-115 26
Ai 0-55 *
AC 55-69 33
C1 69-94 4G
C2 94-139 30
i C3 139+
39 34 25.) 0.93
38 25 31.1 0.80
44 31 30.7 0.72
21 20 0.90
30 25 29.0 0.44
34 27 26.2 0.71
46 231 29.4
39 26 38.2 0.49
40 31 34.7 0.64
42 312 33.0 0.64
Pro-i Ie 4
34 37 14.2 0.84
33 39 11.2
41 33 11.7 0.81
1,3 26 13.0 0.60
Pi ofi le .
41 261 22.5 0.49
30 30 11.9
34 36 22.3 0.45
,-i; : n De th ----.--
Al 0-50 *
A3 50-67 43
IIC 67+ 25
05 .002 <.002
-- --la~ ;-----------
Prof i le
Profi le 10
Sample wouldn't disperse nor determined.
1 Dispersed with NaOCI.
2 Field moist soil dispersed with Pa2dCO.,
I IAl b
I I Alh
A I 2
iulk densi y values for p ofilas 1-6 varied from a lo; of 0.44 /,:c
:.r the Ai Ihorizon of profile 2 and the Al horizon of profile 3 to
rs'i mum of 1.22 9/cc for the I rlb horizon of profile 6. 3ulk .nsit ies
,;are characteristically low. as uxp'-cted for soi is developed fron aolian
pyroclastic materials. 'he lo! e exception of the i lClb '-ori.-cn n n.ioned
above was due to a high sand'content consisting of vitric c~r:c'rs and
other coarse-textired pyroclastic components.
Fifteen-bar water contents were typically high for profiles 1-6
reflecting the voicanic origin of their parent materials. They ranged
from a low of 10.4% in the lidb horizon of profile 6 to a high of 38.2%
in B horizon of profile 2.
Low bulk density values were a reflection of the exceptionally
high porosity of Andosols. High 15-bar H20 contents were a manifesta-
tion of the affinity of allophane for water.
Sand Mi neralogv
The primary mineral content of the 50 500 }j sard fraction rep-
resents the original mineralogical nature of the volcanic ash parent
material as modified by pddcgenetic processes.
The distribution of light minerals n the 1 500 pu fraction is
given in Table S. Quartz was a minor light mineral constituent in all
profiles investigaled. Feldspar jas the dcmineni species observed
generally followed in abLndance by volcanic glass. We3atheiing products
represented difficulty identifiable, higher, ai tcred minerals which may
have been derived from biolt ce and/or Feld.s ar (Luia, 970).
Quartz contents generally displayed erratic distribution with
T e 6. 1." ( O- I .) I .1 I of i l cL,! Colom'bian soil
tor i O : Pir
Al 12 /17
1 15 33
Cl 11 83
C2 7 55
C3 8 78
All S9 45
A12 5 60
A3 2 63
[B]1 19 60
C 16 64
All 4 52
AI2 3 66
C3] 7 30
C 4 68
Al 2 53
A3 3 40
 3 57
C 10 75
AI tr 57
AC 3 64
Cl 1 47
C2 5 45
11C3 6 62
_-!. ;(,;L;1LIs IJQ 5t. q rivc. s . ..- .
'Wa th- Rock
Ic nic crri g frog- Other
311i products ,e its Siort-i mineral
Lr 6 tr
13 tr 20
Prori le 2
Profit e 3
Pro:i ie 4
Table 6. Cont;Inu:d
-He- v rnirn als iin O0 .. tr,.iLparent '_grains
Horn- horn- Hyper-
blende blended A.: ite st tene Zircon Biotice Altered Opaque
95 tr 5 tr tr 17
100 tr tr 3V
96 tr 2 tr 2 12
100 tr r r 12
85 4 tr 9 2 79
87 tr 5 8 25
87 5 8 tr 21
89 4 7 24
88 2 6 2 2 I1
88 6 tr 4 2 17
Prof I le 3
86 3 8 3 3
85 6 9 tr tr 14
66 2 10 19 tr 3 !4
47 cr 10 37 tr 6 22
71 2 7 16 tr 4 23
67 2 13 15 3 15
62 18 18 tr r 23
89 2 4 3 4 32
Profi e 5
87 tr 4 9 tr 12
76 8 16 tr li
64 17 19 tr tr 13
It 2 19 5 0
58 18 18 2 4 6
1!;1 Co.i IJ
"ri.1 O1 ri Cptr
Al 3 36
As 5 32
I IAlb 1 29
lICl 8 31
I IAlb 5 26
AI 5 68
A3 2 80
iIC 17 76
All 9 29
A12 6 38
A13 7 45
AI4 7 33
IIC tr 25
Al i tr 52
Cl 2 i4
81 tr 77
P2c IHD N'D
C KC ND
I CI2 Nr ND
i;.3 ot de .ermined.
Ia in 100 or, ills
V ic<.c e ing frig- Other
I ass pr lcii c ,ts 5 t ii to minerals
Proii le 6
iPr- i le i .
Prefi le 3
Profi !e 9
Table 6. ConLinued
Sr i.neral s in 100 LrnLpare2ntari n ____
Horn- horn- lHyer-
blonde blende Augite scihne Zircon bioti e Altered Opaque
Prof; e 6
42 24 32 2 8
44 tr 18 32 6 0
67 16 9 8 9
73 10 15 tr tr 2 16
44 tr 33 23 -
Profi e 7
87 tr 5 8 tr 4 tr i9
95 tr 3 tr tr 2 tr 36
93 3 2 2 tr tr 47
88 tr 7 tr 3 2 7
77 tr 11 3 6 3 3
85 12 tr 3 6
81 6 8 tr 5 7
80- 6 5 3
15 21 28 -6 9
53 20 27 tr tr 18
33 3 17 33 12 22
32 4 18 34 2 7 1I
16 tr 10 40 I
96 tr 4 -
78 tr 8 12 tr 2 10
86 2 5 7 2 tr 14
94 2 tr 2 14
97 tr tr 3 -
85 2 9 t r 54
I; h profit' 1- I1 pro file i h r, ihi s it,i r l sI eci'es
.1o . '' re ci ''ol ie lir'" n cy
ior qnIrtz c crL ,:h i n i r n j i a l de. QuIirt content
Oxs oe< r v L i 1 ilS 9 d cho upper hor i :o is of
I'o: ssi : ; d ppar s aid th plogiocl s series r. re not Ji Fforen-
Li, :d biut cor: i cd a-nd reported as fldspars. Feldspar ,as present
in grcjt sa ai 'Onts ,^nerally at lower altitudes for profit !es 1-6.
Fi ldspar disL ibutions within these profiles were ro.ostly erratic how-
cver in profiles 1-4 hhoween 2,600 m and 2,730 m there was sonle Lenden-
,y for feldspar to increase wirh depth. Feldspar content of profile 7
iwa shri lr to that of profile 1. Tle content of this species in
profile 8 paralleled that of profit c 6. Profile 9 exhibited uniform
fold- par distribution with the exception of a discontinuity at the Cl
Volcanic iass dncreased w\i th profile depth and increased with
incre-iinj altitude in profiles 1- Profile 6 was highest in class
co-ntnt but did not show trenJas ii th dJpl-h due to deposi tional strati-
fication and possibly t.o rcJ:ced weathering Tntensity at the 3,510 m
jiy 4_Mi neral s
Distributloii o heavy mi; e rai in the 50 00L ;i fraction is shown
;n Table 6. I;-;o blonde w,;as t!-e dominant individual mineral species
for profiles 1-6. The pyroxene group, of which augite and hypersthene
.are rost co.mion species, doT;inated the A ,, As, nd il IA1.lb horizons of
profit e 6. Distribu lio of ih-;e i:e vy lircreol suite in profile 6
supports field identification of lithologic discontinuities. These
data suggest t!ha, the I Alb horizon was developed in n.aterials miner-
alogica ly simi lar to the A1 an-d s horizons. Ti- I !Alb and !I b
horizons probably represent pyroclastic depositions eitther from a dif-
ferent source or variation in roij n cl9-nabr com .Pos i ion from i:le share
HornbT'nde tLcindeds to idecr; e i :h pro file I :ph ar:d ; crei sing
elevation in profils -6. rrofile cxhiibi ted lcwer hornblende con-
tents in contrast to profiles 7, 8, and 10. T-ne pyroxene group
dominated all horizons of profile 9 and hypersthene as an individual
species was essentially equal in quantity to hornblende in the A3, Cl,
and C2 horizons.
Zircon, oxyhornblende, and biotite eore observed occasionally and
only in minor quantities.
Opaque minerals were tabulated separately and were mainly rep-
reFented by magnetite and iron oxide nodules.
Genetic Relations of Sand Mineral Distributions
Abunaance of hornhblende, particularly in the heavy mineral fraction,
is indicative of pa-ent materials in their initial weathering cycle and
of youthful sofIs developinrq in these materials,. MInor quantities of
quartz in :he liqht: i-eral fraction provide additional evidence for
this conclusion. The tendency of hornblende to increase at the expense
of hypersthene and ugi te vi th decreasing elevation indicates that
pedoligic sic ithering has proccceded at a more rap;d pace at lower altitudes.
C ja. Mi ralo0
a ii ati I e es
l;l ::ir 'is be identified through Lhe diffraction of X-rays
Jue to a sivii lit-; between interplanar distance (d-spacing) end wave-
leogrh. The characteristic d-spacing of a specific clay minerall may
Ie czlclted a-,curding to Bregg's law (n = 2d sin 6) since X
(ua'l enr1th) and the anyle e are known. The d-spacing corresionds to
the pln:.e iperpendicu-ar to the c-axis of layer silicates.
T'ie d-spaciny of specific clay minerals will vary predictably ac-
ccrdinj to cation saturation, interlayer liquid (organic molecules)
sorbed on clay surfoccs and the solution from i.,\ch the suspended clay
..as dried (Jackson, 19 ).
Hydrated halloysite was identified by first order spacing of
C1.OA which coill.-ped to 7.41 7.20A after heating a ll-saturated
soeclren to 100C for 24 hours. Metahal loysite was suggested after
Mg-s-turatioe by a /.25A flrst order peak. Vermicalite was concluded
to bo present by the !I-saturation 14A !SA spacing and a 10.0A -
10.2A spacing after hoatint to 00C. Illite was identified by the
presistence of a l.'. pek for all treatments. Figure 3 demonstrates
the technique utii zed to identify vermiculite, i lite, hydrated
Khlloysite, and metahliloysite. The diffractio pattern for the Mg-
saturacd corps cocr ey (0,2 2 r) from horizon A3 of profit e 7 exhibits
pea's at 14.2A, 9.93A, and 7.25A -hi h car be attrlibu'ec tc vermiculite,
Si te--hydrateoi :illoys ite, and r.:etahalloysite, respectively. Heac1ring
of this spec men to 100C for 24 hours re',,ea id J fi action peaks at
appr-oximately the same pic i ions. However it can be assume" Tiat the
Fig. S.--X-ray diffrdccion patterns of mg-saturated
;,i c dry, K-saturatedj,iOOC, ardi K-satuateJ
5CCC treated coarse clay of hcriz'n A3 in
profile 7 demonstrating identification of
!eLart- loysi te, hydrated halloysi t-, i l i te.
and vermiculite by changes in d-spacings.
So. n -h n .1 ,I ria d lloysitae -nd tfha
S* t i c e rn r a ir i rn L'. of c t ,l oy-
i ; i co fIor ihe I u C Iiffr:ction ni tern i figiire 8
S i 1r -. i ri 1' T i Yy ; cr. /, 25A ,-ik an; rccioju iiin ensi y of
S 10, C I 1 I, 1"k T s .ll i A. IA k.-- can e t t ri-Fbu o to illi t .
t I I I,, )!C JLti,'J t:he hai ysi q a l cy n n' a d caused
-. rti l ol ,ii <; of ve 'i- c li cj re to 10. '. A due to d s triuction of hydroxy-
'1 i.. t o rl ;. I A p rtion of the 10.2A peak can be assigned to
ill te ,'l7 ch ;-- .: i ,t 500C.
Non -.:r/s I ll i n si n pecies such as a I lophane l hicih are amoi-phous to
'X-ilys c-a ,ot be i ent i field due to absence of di ff actionn maxima,
Ch -ori te a.!d mon.. Lori l c.i te (s5, cti te) ..-re not i en L field in any of
ohe soi ls i ve iratcd. Peaks i, the 7A region were ino' assiq'ied to
koolinitr a Iu:c to :.hir broadness and 7.2A or greater position. It is
oi lin a :. ''Ler of opinion as Pto *.bhethri components in this region may
he iden'if I d as i. etthalloysite or poorly crystal zed kaolinite.
Obvio;']ly me abha loysi te-porly crystal lized kae l ini te-crystal 1 in
k;ir, i rite continil a exists which complicates assi nment of a species
Cr.-, cbal itoe nd gibbsite rwere ideciL 'id by 4.0"A and 4.33A
sp;:'cinjs, respectively. Spacings of 4.2A and 3.3.A iere assigned to
quartr:P. FI ,ld'.par r. as idontif:e by di ffr cti : peaks in the 3.0 A to
X-ray diffra.ctgra:'s of fira c:ay (<0.2 p) and coar:e clay (0.2 -
2 ,.) frI, rions foe- Fr Fi s -0 lre p ,re noted ;n Figs. 9-ri. Recog-
rizable cr', ta! ina species f, on X--ray diffract;cn p-ters are li sted
in Table / und d/n spci-g5s are rl:,-e:!td in Appendix "cbil 13 for the
ao-o' e. tior~, clay fracl.: n tnd pr; fi l s.
4 5 7 10
Fig. 9.--X-ray diffrac ion pattern of
iM-saturaTed coarse clay
(0.2-2i? anjd Fine clay
(<* ,.2,'-) fra-ctins of profile
F -X6 i on ,
prof? / 2.
dill ,o Ii-S ROitlS
F3 4O--X-ia dF cion 13a7i
clay O,-.2pi) and fine c!.y
(< 2,1) fractios of
AL --- I .
4 5 7 10 17
Fig. il.--X-ray diffraction patterns
of !g-saturated coarse
clay (0.2-2jj) and Fine
clay (<0.2i) fractions of
profit l 3.