PertanikaJ. Trap. Agric. Sci. 26(2): 79 - 88 (2003) ISSN: 1511-3701© Universiti. Putra Malaysia Press

Weathering Behaviour of a Basaltic Regolith from Pahang, Malaysia

J. HAMDANa , M. PELP & B. RUHANAbaDepartment of Land Management, Universiti Putra Malaysia,

43400 UPM, Serdang, Selangor, MalaysiabDepartment of Management and Marketing, Universiti Putra Malaysia,

43400 UPM Serdang, Selangor, Malaysia

Keywords: Regolith, weathering, saprolite, elemental mobility

ABSTRAK

Giri-ciri dan kadar luluhawa pada regolit saprolit dalam terluluhawa yang terbentuk daripada batuan basalttelah dikaji. Jujukan regolit tanah-saprolit-batu sedalam 15 m yang terletak di bahu jalan di Pahang, Malaysia,telah dipilih untuk tujuan ini. Kadar luluhawa pada regolit ini telah dinilai dengan beberapa indisis luluhawa,perubahan pada sifat kimia-jizik tanah, mineralogi lempung dan ciri-eiri mikrofabrik. Kesemua nilaian telahmembuktikan bahawa kadar luluhawa adalah tinggi dan cepat, walaupun di peringkat pembentukan saprock.Kehilangan keterlaluan elemen utama seperti K, Na, Ga, dan Mg, dan penambahan jelas oleh Fe, Ti, Gu danNb berlaku semasa proses saprolitizasi, mungkin menjelaskan bentuk luluhawa yang tinggi pada regolit tanahini.

ABSTRACT

The characteristics and degree of weathering in a deep saprolitic regolith developed on basalt were investigated.A 15 m deep regolith of soil-saprolite-rock sequence, located along a new road cut in Pahang, Malaysia, wasselected. The intensity of weathering in this regolith was assessed lJy various weathering indices, as well as lJythe changes in the physiarchemical properties, clay mineralogy and the microfabric characteristics of the profile.All assessments gave strong evidences of intense weathering, even at the stage of saprock formation. Extremedepletion ofmajor elements such as K, Na, Ga and Mg, and significant enrichment ofFe, Ti, Gu and Nb occurredduring saprolitization process, and, these perhaps explain the extreme weathering pattern of this regolith.

INTRODUCTION

The extent to which particular elements aremobilized during weathering depends upon thecontrol of solubility in aqueous solutions andtheir interaction between these solutions andthe complex surfaces of primary and secondaryminerals. Thornber (1992) reported that cationswere more mobile at low pH while anions weremobile at higher pH.

Weathering and mineral transformation areimportant phenomena in the arena of theMalaysian soils. Roe (1951) first reported theobservations of weathering profiles in PeninsularMalaysia. An intensive study on soil formationand its variation with altitude throughout thepeninsula was investigated by Burnham (1978).Eswaran and Wong (1978) and Yeow (1975),made some detailed studies on the chemical,

mineralogical and micromorphological changesrelated to the transformation of parent rocks tosoils in granite. Study on metamorphic rocks wasconducted by Stoops et al. (1990), and Zauyah(1986). The genesis of basaltic soils was reportedby Ives (1966), and West and Dumbleton (1970),who concluded that the basaltic rocks wereformed probably during the middle Eocene age.

The present basalt regolith studied wascomposed of the soil-transition zone-saprolite­rock sequence. The saprolite, that is theweathered rock, comprised the largest portionof the regolith, and is increasingly important tothe Malaysian upland plantation industry. Theunavoidable terracing during crop planting androad construction activities, landslides anderosion had exposed these materials to or nearthe surface and become accessible to roots. This

J. HAMDAN, M. PELI & B. RUHANA

paper describes the degree of weathering andchanges in the regolith characteristics under thehumid tropical, well drained conditions ofPeninsular Malaysia.

MATERIALS AND METHODS

Location and Geological Setting

The selected regolith developed on basalt islocated in Pahang state on the West coast ofPeninsular Malaysia. The geological study byHutchison (1973), suggested that the extrusionof basaltic lava occurred during the Quaternaryage and it overlies and surrounds the granitichills to the north and northwest of Kuantantown. The rock is compact, microcrystalline, andgreenish black vesicular olivine basalt. Theclimate is equatorial with an annual precipitationof 3660 mm and potential evapotranspiration of1,130 mm. The soil moisture regime is udic andthe soil temperature regime is isohyperthermicwith the mean annual soil temperature of28.7 °C. The landscape is gently undulating andthe profile was sampled on a new road along theroad from Kuantan to Sungai Lembing, about 8km from Kuantan town. A profile of about 15 mdeep (Fig. 1) was horizonated and morphologically

DEPTH (H)

o~~....,."..,,.,.,......,, ApB210x

.• •. Cl

-4 . I ., .. . .

C2

Cr.!

Cr2

described following the criteria of the USDA(1981). The profile is classified as fine, clayey,kaolinitic, isohyperthermic, typic Acrudox (SoilTaxonomy 1996). Bulk samples and undisturbedsamples of soil, saprolite and rock were takenfor various analysis.

Labaratory Analysis

The bulk samples were air-dried and were passedthrough a 2 mm sieve. The undisturbed coresamples were taken for the bulk densitydetermination. The pipette method wasemployed to estimate the soil texture and thewater dispersible clay (WDe) was determined bysuccessive sedimentation method (Tessens 1984).Soil pH was measured in suspension of 1:2.5soil:solution ratio, while pH in sodium fluoridewas estimated after stirring vigorously for twominutes (Rayment and Higginson 1992). Themethod proposed by Ferrari and Megaldi (1983)was used to determine the soil abrasion pH. AllpH readings were recorded using a glasselectrode pH meter. Soil organic carbon wasdetermined by the Walkley-Black dichromatetitration method and nitrogen by macro-kjedahldigestion procedure (Bremner and Muliraney

SOLUM

PEDOPLASMATION

UPPER SAPROLITE

LOWER SAPROLITE

SAPROCK

ROCK

80

Fig. 1: A schematic sketch oj a basalt profile

PERTANIKAJ. TRap. AGRIC. SCI. VOL. 26 NO.2, 2003

WEATHERING BEHAVIOUR OF A BASALTIC REGOLITH FROM PAHANG, MALAYSIA

1982). The free Fe content was extracted bydithionite-citrate-bicarbonate method of Mehraand Jackson (1960). For the CEC andexchangeable bases determination, the leachingmethod with 1M ammonium acetate buffered atpH 7 was used. The determination of aluminiumand P sorption index were done following thealuminon method (Hsu 1963) and Bache andWilliams (1971), respectively. The bulkmineralogy of the clay fraction of the soils andsaprolites were analyzed by x-ray diffraction. Soilcharge characterization was determined bypotentiometric titrations and ion retentionmethods (Uehara and Gillman 1981).

Undisturbed samples from major horizonswere collected in Kubiena boxes of 55 x 75 x 50mm size. These samples were air-dried andimpregnated with resin (araldite). Thin sectionswere prepared and described using theterminology outlined by Bullock et al. (1986) .The major elemental chemical content of basaltrock and its weathering product were analyzedwith the Inductively Coupled Plasma (ICP). Anisovolumetric calculation was performed todetermine the intensity of weathering throughelemental mobility, converting the percentageweight chemical analysis to volume-basedconcentration by multiplying with the bulkdensity of the respective sample. Using theunweathered bedrock as the reference, absolutepercentage gains and losses of each elementwere then calculated. The weathering indices ofParker (1970), Rock Alteration Index by Eswaranet al. (1973), and the Molar ratio and abrasionpH by Ferrari and Megaldi (1983), were adoptedto evaluate the degree of weathering of thisprofile.

RESULTS AND DISCUSSION

Morphological Descriptions

A su.m~ary. of the profile morphological?escnp~onsIS presented in Table 1. The profileIS prommently characterized by clayey yellowishbrown solum. The surface layers have a strongcrumb that changes gradually to weak subangularblocky structure in the subsoil horizons. Theconsistency is friable and fluffy but becomesfirm towa~ds the up~er saprolite layer. Drainageof the soIl profile IS somewhat excessive. Thesaprolitic layers are well weathered, yet massive,clayey, slightly friable but increase in firmnesswith depth, and become more coherent towardsthe rock. The upper saprolites are variegated incolors of mostly dark brown with reddish andgrayish patches, but becomes more gray andgreenish with depth towards the saprock. Thedrainage of the saprolite layers is somewhatimperfect.

Physic~ChemicalCharacterization

The selected physico-chemical properties of theprof~e are presented in Table 2. The profile isphYSICally characterized by the high clay contentthroughout the regolith, with the content in thesolum of > 70% while the saprolite of > 60%.The high clay content did not coincide with thevery friable and fluffy consistency of the solumlayers observed in the field, and this wouldsuggest strong aggregation of clay by iron toform pseudosands and clayballs (Paramananthan1977). Log clay percent (Fig. 2) roughly followsa strai~ht line pattern in the saprolitic layers,suggestmg that the presence of clay is mostprobably d~e to weathering (Eswaran and Wong1978). ThIS assumption is supported by the low

TABLE 1Morphological characteristics of a basalt regolith

Horizon Depth Texture Color(m)

Matrix Mottles

Soil 0-2 Clay 10YR4/4 nilTransition 2 - 3 Clay 10YR3/4 nilUpper saprolite 3 - 6 Clay 2.5YR3/4 10YR4/1Middle saprolite 6 - 10 Clay 2.5YR3/4 10YR4/1Lower saprolite 10 - 15 Silty clay 2.5YR3/4 nil

Consistency

Friable-FluffYFriableFriableFirmHard

Structure

Crumb-SABSAB

MassiveMassiveMassive

PERTANIKAJ. TROP. AGRIC. SCI. VOL. 26 O. 2, 2003 81

00N)

TABLE 2'i:i Selected physico-chemical characteristics of a basalt regolithtrJ

~~ Horizon Clay Log B.D WDC CEC Exchangeable Bases PC PDC %O.C %N Fed P Al Soil pH

c......,

~% Clay % (g/cm3

) % (cmol (+)/kg soil) (cmol(+)/kg clay) % Sorption

~':-' Index..., Ca Mg K Na pHw pHKCL ApH

t::l~ v~;0

> ~0 Ap 78 1.9 0.98 33 6.2 0.87 0.59 0.28 0.11 2.5 23.0 2.60 0.27 12.4 78 0.01 5.34 4.79 -0.55 'i:i~ trJP B20x 80 1.9 1.09 0.4 2.2 0.30 0.05 0.09 0.05 1.0 20.1 0.86 0.13 12.5 82 0.01 4.81 4.52 -0.32 t:rJ) p;oP BC 66 1.8 1.37 0.4 1.1 0.26 0.05 0.05 0.05 0.8 23.1 0.06 0.02 14.9 82 0.01 5.14 5.44 0.30

t:J:j<:

Upper saprolite 64 1.8 1.17 0.3 2.9 0.29 0.04 0.09 0.03 1.3 22.8 0.02 0.01 12.5 82 0.04 4.84 4.47 -0.370~r

Middle saprolite 57I\D 1.8 1.07 0.1 3.0 0.28 0.06 0.06 0.02 3.9 22.5 tr tr 12.3 78 1.97 4.73 4.11 -0.62

~0'>

Z Lower saprolite 30 1.5 1.17 0.1 5.7 0.27 0.09 0.06 0.02 15.7 45.4 tr tr 12.5 71 3.64 4.61 3.92 -0.699,!'O Rock nd nd 2.41 nd nd nd nd nd nd nd nd nd nd nd nd nd nd nd ndN)00<.10

Note: B.D - Bulk density, WDC - Water Dispersible Clay, CEC - Cation Exchange Capacity, PC - Permanent Charge, PDC - pH Dependent Charge,O.C - Organic carbon, N - Nitrogen, Fed - Dithionite extractable ferum, Al - Aluminium.

WEATHERI G BEHAVIOUR OF A BASALTIC REGOLITH FROM PAHANG, MALAYSIA

WDC values in these layers which range from 0.1to 0.5%. The silt to clay ratio (Fig. 2) shows acurvilinear pattern with depth, being maximumat the lower saprolitic layer, and decreasingtowards the solum. The decrease from thesaprolitic layer towards the surface horizonspoints to the increase in weathering and soilformation (Van Wambeke 1962). The two phasecurvilinear patterns as observed by Eswaran andWong (1978) on a deep granitic profile werenot detected in this profile, suggesting that thisprofile may experience extreme stage ofweathering. This is supported by a drastic changein bulk density that occurs between theunweathered rock (2.41 g/cm3

) and the saprocklayer (1.17 g/cm3).

Intense rainfall and high temperature alongthe east coastal region of the peninsula resultedin a higher rate of organic matter decompositionand mineralization. The plot of log organic

carbon shows a curvilinear distribution. The nickpoint appearing at 2.5 m corresponds to theseparation of the pedological from saprolitelayers (Singh and Singh 1987). The organiccontent is very low in the saprolite and could beattributed to its migration along fissures andremnants of cracks in the saprolite (Stone andComerford 1994). The soil pH shows a decreasewith depth, and could be attributed to the effectof organic matter content and degree ofweathering. This is also supported by the drasticchange in the abrasion pH values in Table 6.The DpH data indicates a positive value at thetransition zone, suggesting the dominance ofpositive charge. Further study on the surfacecharge properties (Table 3) shows that values ofthe point of zero net charge (PZ C) are higherthan the zero point of charge (ZPC or pHo)

values throughout the profiles, except for thesurface horizon where the organic matter content

2

1.5

0.5

-0.5

-1

-1.5

-2

4 6 8. toHbriZondepth (m)

-x- Silt/ClayRatio

~log%Clay

---6-Log % G.C

Fig. 2: Depth junction or related soil properties

TABLE 3Surface charge characteristics of a basalt regolith

Horizon PZNC NegativeCharge

PositiveCharge

(f.tmol(+)/g soil)

NetCharge

Ap 3.71 4.17 -20.01B20x 5.29 4.35 -13.57Upper saprolite 5.85 3.91 -14.01Middle saprolite 5.69 3.85 -13.14Lower saprolite 3.74 3.65 -17.88

15.4615.7116.0116.4518.13

-4.542.142.013.310.25

Note: PZNC - Point of zero net charge, PZC - Point of zero charge.

PERTANIKAJ. TROP. AGRIC. SCI. VOL. 26 0.2,2003 83

J. HAMDAN, M. PELI & B. RUHANA

is higher. Similarly, the positive charge valueswere also found to be higher than the negativecharge values at these horizons. The presenceof positive charge indicates that the soilexperiences extreme weathering stage (Tessensand Zauyah 1982; Van Wambeke 1992).

The PC and PDC values do not demonstrateincrease with depth. The almost constant valuesmay suggest little change in mineralogy as aresult of intense weathering even at the lowersaprolite layer. The CEe values are extremelylow, except for the surface horizon where organicmatter is abundant. The exchangeable bases forthe whole regolith also point to a similardistribution pattern. In the east coastal areas ofPeninsular Malaysia where rainfall andtemperatures are high, weathering may reachgreat depth. Most of these bases may have alreadyleached away even at the initial stage of saproliteformation (Burnham 1989).

Clay Mineralogy

Fig. 3 shows the results of the x-ray diffraction ofthe clay size fraction of the basalt profIle. Only

traces of primary minerals such as feldspar andolivine is detected in the saprolite layers. In thesolum layers, strong peak for goethite andgibbsite are observed. The peak for gibbsite isweak in the saprolite layers, suggesting that mostaluminium is well crystallized in soil materials.The low aluminium content in the soil asdetennined by aluminon method, may also pointto a similar conclusion. Kaolinite peak isdistinctively high in all horizons, suggesting thatmost weatherable minerals such as feldspar andolivine are well weathered into clay minerals,even at the lower saprolite layer.

The diffraction pattern of the profIles showsthat the main bulk of the soil mineralogy is notdetected. It is suspected that a reasonable amountof x-ray amorphous materials are present in theprofile but is not detected by the diffractogramtechnique. The assumption is supported by therelatively high values of soil pH in IN NaFsolution, particularly in the saprolite.

From the study, the transformation ofminerals from rock-saprolite-soil for basalt profIle,can be proposed as follows:

RockOlivine

Saprolite-----. Goethite

Chlorite

Soil~Goethite

Goethite

Go

G.

G.

L-- l- . l l l._. .--L.'_---'2i -J) '~I -is -II

Fig. 3: The x-ray diffraction pattern of the Mg saturatedclay size fraction of a basalt profile (Note: M-mica, Gi­

gibbsite, Q-quartz, K-kaolinite, Ge-goethite)

Augite -----. Goethite ----. GoethitePlagioclase~ Plagioclase ----. Kaolinite

Kaolinite ~ kaoliniteGibbsite ----. Gibbsite

Opaque -----. Opaque ~ Opaque....... Goethite

Microfabric Observation

The study of the profIle shows drastic changes inthe microfabric of the rock-saprock-saprolite-soilsequence. The fIne-grained basalt rock iscomposed of microphenocrysts of plagioclase,olivine and pyroxene. The groundmass iscomposed of the same three minerals togetherwith roughly rectangular magnetite minerals. Atthe saprock zone, the olivine and pyroxeneminerals are moderate to well altered. The matrixhas an undifferentiated b-fabric and an openporphyric c/frelated distribution pattern (RDP),suggesting that a certain amount of clayformation is already occurring at this layer. Themassive saprock gradually developed into vughymicrostructure, with the void size < 1 mm, andincreased in porosity from 8% to 15%. Most

84 PERTANIKAJ. TRap. AGRIC. SCI. VOL. 26 NO.2, 2003

WEATHERING BEHAVIOUR OF A BASALTIC REGOLITH FROM PAHANG, MALAYSIA

primary minerals in these saprolite zones arewell weathered into dark brown dayey matrix.Pseudomorphs of olivine and pyroxene are rare.The total porosity increases to approximately50% in the soil layers, comprising dominantlypacking voids. Abundant of opaque mineralsand some quartz are observed. Only very fewsubhedral olivine and pyroxene are seen coatedby iron oxides that may have protected them

from weathering. The b-fabric and RDP remainthe same throughout the profile.

Elemental Mobility

A study of elemental mobility during saproliteformation was conducted using isovolumetricmethod. The results are presented in Fig. 4 andTable 4.

40

5102

~-,oaOJ

........Fe203

--'-'002_MoO-a--CaO

_"'gO_Ne20

-&--K20

-+--P205

--+-1.1... 10$1

Saprock zone20

-60 +

-40 ..

-1 00 ~--o---.".-...-;;;-e-;;;;;;;;;;;;;;;;;;;;;;;;;~;;;;;;;;;;;;;;;;;~

Fig. 4: The loss and gain of elements during the formation of saprolite

TABLE 4The isovolumetric loss and gains of major and trace elements during

rock transformation into saprolite

Element Elemental content (cg em-I) Loss (-) and Gains (+) of elements (%total elemental content in rock)

Rock Saprolite Rock - Saprolite

Major elementSi02 19.0 34.0 -72Al20 3

39.0 33.0 -16Fe20 3

29.0 33.0 12Ti02 4.3 5.2 21MnO 0.5 0.1 -82CaO 21.0 0.2 -98MgO 15.2 0.3 -98Na

20 6.2 0.1 -99

~O 3.3 0.0 -100

P20S 1.3 0.3 -79

Trace elementBa 925 51 -95Cr 1920 448 -77Cu 77 182 136Nb 36 75 108Ni 241 212 -11Sr 1356 24 -98V 438 338 -23y 84 8 -90Zn 342 149 -57Zr 361 309 -14Bulk Density 241 117(cg/cm3

)

PERTANIKAJ. TROP. AGRIC. SCI. VOL. 26 NO.2, 2003 85

J. HAMDAN, M. PELI & B. RUHANA

i. Mobility of Major Elements

The transformation of rock to saprolite hasresulted in a total mass loss of 57.8%. Duringbasalt weathering, most of the rock constituentsare depleted significantly even at the initial stageof weathering, i.e. saprock formation. Silicadepletes abruptly from 66% to 76% during thesaprock and saprolite formation, respectively,and this accounts for 62% of the total mass loss.Aluminium demonstrates a gradual loss of 18 to26%. Manganese and phosphorus decreasedrastically in the saprock and are almost totallydepleted in the saprolite. There is absoluteimpoverishment of potassium, calcium,magnesium and sodium during saproliteformation. Ferum and titanium show a slightdecrease during saprock formation, but a markedenrichment in the saprolite formation. Themarked depletion of these cations from thesaprolite, as reported by Ferrari and Megaldi(1983), may have resulted in low soil abrasionpH (Table 5). The magnitude of the majorelement depletion in this profile, with decreasingorder, is: K, Na, Ca , Mg > Mn , P > Si > Al > Fe,Ti.

ii. Mobility of Trace Elements

Among the trace elements studied, strontium,barium and yttrium are most mobile, in which>90% are depleted from the saprolite. Thesequence of trace element mobility, withdecreasing order, is: Sr > Ba > Y > Cr > Zn > V> Zr > Ni > Cu, Nb. Copper and nobium indicateenrichment in the saprolite.

From the study, the mobility of the variouselements in basaltic profile can be summarizedas follows:

Most mobile: ~o, Na20, CaO, MgO, Sr, Ba,

andYIntermediate: MnO, P

20

S' SiO, Cr, and Zn

Least Mobile: A403' V, Zr, and NiEnrichment: Ti0

2, Fe

20 3, Cu, and Nb

Weathering Pattern

Various weathering indices were analyzed andassessed for their applicability to determine thedegree of weathering in basalt profile (Table 5).All indices show a very drastic change in thedistribution pattern with depth at the saprockzone, obviously suggesting that an intense stageof weathering has occurred even at the earlyweathering of basalt. At this point, it is possibleto say that basalt rock may have actuallytransformed directly into saprolite. The highweatherability of basalt in humid tropical climate,as in the study area, may have resulted in suchphenomena. The weathering pattern in thesaprolite and soil layers show a gradual change,yet already at the extreme stage.

CONCLUSIONS

The study suggests that weathering in this profileis intense and rapid, even at the lower saprolitelayers. This is indicated by the changes in thephysico-chemical properties, chargecharacterization, and drastic transformation ofweatherable minerals into secondary forms. Theregolith is characterized by drastic change inbulk density and soil abrasion pH values, highfree iron content and P sorption index, as wellas low aluminium content. The low CEC andbase saturation, even at the deepest horizons,suggest that extensive leaching has taken place(Burnham 1989; Hamdan 1995), attributed to

TABLE 5The degree of weathering as determined by various weathering indices

Horizon Molar Ratio Silt/Clay WIP Abrasion RAJSiO/Al20 3

Ratio pH

Ap 1.14 0.16 0.17 4.20 3.50B20x 1.11 0.16 0.90 4.50 3.40BC 1.29 0.21 1.30 4.80 3.20Upper saprolite 1.66 0.32 1.40 4.80 2.10Middle saprolite 1.81 0.35 1.50 4.80 1.60Lower saprolite 2.18 1.86 2.00 4.95 1.53Rock 5.22 nd 104.4 8.90 0.44

Note: WIP - Weathering Index of ParkerRAI - Rock Alteration Index

86 PERTANIKAJ. TROP. AGRIC. SCI. VOL. 26 NO.2, 2003

WEATHERING BEHAVIOUR OF A BASALTIC REGOLITH FROM PAHANG, MALAYSIA

the significant depletion of bases duringsaprolitization. This may explain why soils inthe humid tropics are relatively low in fertility(Hamdan and Burnham 1996). In this case, thecontribution of nutrients from basalt weatheringseems insignificant. The atmospheric inputs andthe recycling of organic inputs are thereforeimportant to sustain minimum level of soilfertility in the tropics. The mineralogy of theparent rock as well as climatic influence, perhapsattribute markedly to accelerate weatheringprocesses in this soil type, that consequentlydoes not reflect its age of deposition (Hutchison1973) .

REFERENCES

BACHE, B. W. and E. G. WILLIAMS. 1971. Aphosphate sorption index for soils. J SoilSci. 22: 289-301.

BREMNER, J. M. and C. S. MULLRANEY. 1982.Nitrogen total. In Methods of Soil Analysis,ed. A. L. Page. Part 2. 2nd edition. (ed.),Agron. No.9., Amer. Soc. Agron. and SoilSci. Soc. Amer., Madison, WI.

BULLOCK, P., N. FEDOROFF, A.JONGERIUS, G. STOOPS,T. TURSSINA and U. BABEL. 1986. Handbookfor Soil Thin Section Description.Wolverhampton: Waine ResearchPublications.

BURNHAM, C. P. 1978. Soil formation and itsvariation with altitude in Malaysia andWestern Sabah. Ph.D Thesis, Wye College,University of London.

BURNHAM, C. P. 1989. Pedological process andnutrient supply from parent materials intropical soils. In Mineral Nutrients in TropicalForest and Savanna Ecosystem, p. 27-41. Specialpubl. No. 9 of British Ecological Society.Oxford: Blackwell Scientific Publ.

EswARAN, H., and C. B. WONG. 1978. A study ofdeep weathering granite in PeninsularMalaysia. Soil Sci. Soc. Amer. J 42: 144-158.

EswARAN, H., G. STOOPS and P. DEPAEAE. 1973. Acontribution to the study of soil formationon Isla Santa Cruz, Galapagos. Pedologie 23:100-122.

FERRARI, G. A. and M. MEGALDI. 1983. Degree ofsoil weathering as determined by abrasionpH: application in soil study andpaleopedology. Pedologie 33: 93-104.

HAMDAN, J. 1995. Saprolite and soil fertility inthe humid tropics (Malaysia). Ph.D Thesis,Wye College, University of London, UnitedKingdom.

HAMDAN, J. and C. P. BURNHAM. 1996. Thecontribution of nutrients from parentmaterial in three deeply weathered soils ofPeninsular Malaysia. Ceoderma 74: 219-233.

Hsu, P. F. 1963. Effect of initial pH, phosphate,and silicate on the determination ofaluminium with aluminon. Soil Sci. 96: 230­238.

IVEs, D. W. 1966. A weathering sequence onMalaysian soils derived from basic effusiverocks. In Proc. of the Second Malaysian SoilConf, p. 114-22. Kuala Lumpur.

MEHRA, O. P. and M. L. JACKSON. 1960. Ironoxide removal from soils and clays by adithionite-citrate system buffered withsodium bicarbonate. Clays and Clay Minerals7: 317-327.

PARAMANANTHAN, S. 1977. Soil genesis on igneousand metamorphic rocks in Malaysia. Ph.DThesis, Univ. of Ghent, Belgium.

PARKER, A. 1970. An index of weathering forsilicate rocks. Ceoi. Mag. 107: 501-504.

RAYMENT, G. F. and F. R. HIGGINSON. 1992.Australian Laboratory Handbook of Soils andWater Chemical Methods. Melbourne: InkataPress.

ROE, F. W. 1951. The geology and mineralresources of the Frasers Hill area, Selangor,Perak and Pahang, federal of Malaya, withan account of the mineral resources. Mem.5 geol. Survey, Fed. Malaya.

SINGH, A. K and B. SINGH. 1987. Soil propertiesas a function of depth in a deep weatheringprofIle on gneiss under natural Sal (Shorearobusta) Forest of South Faipur (M.P). 1.Physico-chemical properties. J of TropicalForestry 3: 336-343.

SOIL SURVEY STAFF. 1996. Keys to Soil Taxonomy.Seven edition. Washington, DC: U.S.Department ofAgriculture Soil ConservationService.

STOOPS, G., SHI GUANG CHUN and S. ZAUYAH. 1990.Combined micromorphological study of a

PERTANIKAJ. TRap. AGRIC. SCI. VOL. 26 NO.2, 2003 87

J. HAMDAN, M. PELI & B. RUHANA

laterite profile on graphite sericite phyllitefrom Malacca (Malaysia). Bull. De La Soc.Belge de Geologie 99-1: 79-92. Brussel.

STONE, E. L. and N. B. COMERFORD. 1994. Plantand animal activity below the solum. InWhole Regolith Pedology, ed. D. L. Cremeens,R. B. Brown and]. H. Huddleston, p. 57-74.SSSA Special Publication o. 34, Madison,Wisconsin, USA.

TESSENS, E. 1984. Clay migration in upland soilsof Malaysia. J Soil Sci. 35: 615-624.

TESSENS, E. and S. ZAUYAH. 1982. Positivepermanent charge in oxisols. Soil Sci. Soc.Amer. J 46: 1103-1106.

THORNBER, M. R. 1992. The chemical mobilityand transport of elements in the weatheringenvironment. In Handbook of ExplorationGeochemistry: Regolith Exploration geochemistryin Tropical and Subtropical Terrains, ed. C. M.R. Butt and H. Zeegers, 4: 79-96. Amsterdam:Elsevier.

UEHARA, G. and G. P. GILLMAN. 1981. TheMineralogy, Chemistry and Physics of TropicalSoils with Variable Charge Clays. Boulder,Calorado: Westview Press.

USDA. 1981. Soil survey manual. Revision ofchapter 4: Examination and description ofsoils in the field. 430-V-SSM.

VAN WAMBEKE, A. 1962. Criteria for classifyingtropical soils. J Soil Sci. 13: 124-132.

VAN W AMBEKE, A 1992. Soils ofthe Tropics: Propertiesand AppraisaL New York, NY: McGraw-Hill.

WALKLEY, A. and I. A. BLACK. 1934. Anexamination of the Degtjareff method fordetermining soil organic matter and aproposed modification of the chromic acidtitration method. Soil Sci. 37: 29-38.

WEST, G. and]. ]. DUMBLETON. 1970. Themineralogy of tropical weathering illustratedby some West Malaysian soils. Q. J Eng. Geol.3: 25-40.

YEOW, Y. H. 1975. Weathering of rocks in humidtropical condition. Ph.D Thesis, Universityof Malaya, Malaysia.

YIN, E. H. 1976. Geological map of Kuala Lumpurarea. Sheet 94, scale 1:63,360. DirectorateNational Mapping, Malaysia

ZAUYAH, S. 1986. Characterization of someweathering profiles on metamorphic rocksin Peninsular Malaysia. Ph.D Thesis, Univ.of Ghent, Belgium.

(Received: 27 May 1998)(Accepted: 21 August 2003)

88 PERTANIKAJ. TRap. AGRIC. SCI. VOL. 26 NO.2, 2003