ie encineerinc ceo oc icacescris:ion o'car oona esui:eroc<sane soi sby A. D. BURNETT", PhD, DIC, MIMM, FGS, and R. J. EPPS>, BSc ARSM, FGS

MOST EXISTING systems of carbonateclassification tend to use terms that areunfamiliar and confusing to engineers.Any scheme that is to be acceptable inengineering geology must therefore beboth simple and unambiguous. This reviewof carbonate nomenclature will attemptto develop a scheme of carbonate des-cription which is both simple and geo-logically accurate, and to draw attentionto those features of carbonates which maybe of engineering significance.

Review of classification schemesThe description of limestones depends

largely on the purity of the limestonewhich should, therefore, be classified on atwo-fold basis:(1) according to mineral composition;i.e., if purely carbonate the specific min-eral type such as calcite, aragonite, dolo-mite, etc., or where contaminated by non-carbonate minerals, the degree of con-tamination of those materials;(2) according to textural composition;i.e. grain size, grain type, degree of sort-ing and packing, which reflects the depo-sional origin.

Pure carbonatesThe majority of systems developed for

the description and classification of car-bonates stem from the interest of thepetroleum industry in these rocks. Conse-quently, factors such as depositionalorigin, facies and porosity are of impor-tance and descriptions are largely basedon texture. The two classifications mostwidely used by geologists are those ofFolk (1959, 1962) and Dunham (1962) .Folk's classification attempts to embraceall common carbonate rocks and there-fore includes more terms that Dunham's,which is solely based on texture.

Folk bases his classification on the factthat limestones are composed of threeend members —"allochems", microcrystal-line ooze (micrite) and sparry calcitecement. Allochems are of four types-intraclasts, ooli'tes, fossils and pellets. Theterm intraclast is applied to fragments ofpenecontemporaneous, generally weaklyconsolidated sediment that has beeneroded from adjoining parts of the seafloor and redeposited. Fine in'traclasts arefrequently mis'identified as pellets, whichhave an upper size limit of 0.15mm.

The classification is based on the pro-portion of the three end members, and onthe proportion of the components in theallochemical constituent. Each class oflimestone may then be further d'ividedinto eight groups according to their de-positional maturity, reflecting in part theirenvironment or origin.

Dunham's classificat'ion is primarily

eoirector, and l)formerly geologist, EngineeringGeology Ltd., Teknis House, Meadrow, Godalm-ing, Surrey.

concerned with depositional texture, andthe nature of the predominant allochemsis indicated by "foraminiferal", "skeletal",etc. The terms packstone, grainstone,mudstone, etc., should also be qualifiedby compositional terms such as lime,carbonate or dolomitic. The textural basisof the classification is whether the rockis grain supported or matrix supported.

Leighton and Pendexter's classification,proposed in 1962, considers three vari-ables: grain size, the proportion of matrixto allochemsf and the degree of dolo-mitisation. The different types of allo-chems that may be present are shown inTable I (and the degree of dolomitisationin Fig. 1). The term detrital is applied tograins of limestone derived from an olderrock and to fragments eroded penecon-temporaneously. Lumps also correspondsto the intraclasts of Folk's classification,such as composite fragments, whilst coat-ed grains refers to oolites, pisolites andother algal encrusted fragments,

Impure carbonates and admixturesof carbonates

Limestones are defined as those rockscomposed of more than 50'/9 carbonateminerals, of which 50'/9 or more consistof calcite and/or aragonite. The classifi-cation of impure limestones and dolomitesaccording to composition is best achievedby the use of ternary diagrams. Leightonand Pendexter (1962) proposed a ternaryclassification between limestones, dolo-m'ites and other impurities along theselines (Fig. 1).

Fookes and Higginbottom (1975) havealso evolved a similar classification oflimestones, sandstones and shales, withadditional binary diagrams not coveredby the triangular diagram and using analternative clay-limestone spectrum. (Figs.2 at 3).

Fookes and Higginbottom have pro-posed a classification of carbonates foreng'ineering purposes, which is based ontexture and the degree of induration andtherefore strength as is shown in TableII. This, therefore, also classifies differenttypes of carbonates in the unconsolidatedstate.

The spectrum between limestones anddolomites has been subdivided by Petti-john (1956), and in greater detail bySchmidt (1965) as shown in Fig. 4.

Proposed classification forengineering purposes

A mistake that is commonly madein devising systematic classifications of

tThis parameter is measured by the Grain toMicrite Ratio (GMR) according to the followingequation:

%%d (detrital grains + skeletal grains +pellets + lumps + coated grains +

mineral grains)GMR =

/ micrite

rocks is in believing that a name canreplace a thorough rock description. Thepreceding paragraphs illustrate the diver-sity of terms that have been used toclassify carbonates. For engineering pur-

nur trna

Calcareous

Siltstone

Silty

Limestone

10ea 50;r10e'i

ti!ei

0cnc0

Cs

Ca I ca reo us

Conglomerate

Conglomerate

Limestone

(al Classification of indurated silt carbonateand gravel-carbonate sediments.

Pure Limestone

20

Marly Limestone

35

Limey Marlstone

MAR LSTONE

65

80

Clayey Marlstone

Marly Claystone

95Pure Claystona

(bl Classification of indurated clay-carbonate sediments.

Fig. 2. Higginbottom and Fookes'omposi-tional cfassification of impure carbonatesedhments

March, 1979 41

10// 10Dot o Lime/ Carr., reous Dolo ru Dolominc Lnnestunemite/ 't stonr sv

9 1 1 1 Dolomite Calcite 1 9 0100'. 90". 909 Dolomite". lou 0"

"An appropriate compositional term should besubstituted for the word "impure"

Fig. 1. Leighton and Pendexter's composi-tional terminofogy for carbonate rocks

poses the properties that are of signific-ance are the degree of cementation andstrength, the grain size and porosity, andother criteria as described by the Engin-eering Group of the Geological Soc-iety (Anon 1970, 1972). In addition, var-ious contaminants such as gypsum, chertor clay may be of significance in certaincircumstances.

Purely geological descriptions of soiland rock materials are of limited use tothe civil engineer or quarry manager. Ac-cordingly it is necessary to describe bothsoils and rocks using terminology thatindicates mass or bulk and material pro-perties that are of significance in an ap-plied sense.

The general recommended approach isto prefix the main soil or rock name withterms that indicate principally structure,weathering, cementation and grain char-acter and then to add suffixes to indicateengineering properties. Rock materialnames are kept simple but accurate andsoil names follow standard soil mechanicspractice.

Working parties of the EngineeringGroup of the Geological Society of Lon-don have recommended and defined a rangeof terminology to be used and the follow-ing scheme of description is suggestedwhen dealing with the carbonate suite ofrocks and soils, particularly as encoun-tered in the Middle East and North Afri-can Coast.Preffxes to main nameColour

It is possible to use either the Munsell

CARBONATE

Colour Chart or a qualitative description.The former allows comparison of a rockchipping at natural moisture content withan extensive range of standard colourswhich have both a word and a numericaldescription (i.e. hue, value and chroma).The latter comprises choosing a maincolour from column 3 and supplementingthis with terms from columns 1 and/of 2.

1 3white

2pinkishreddish

yellowishbrownishgreenish

bluish

pale creambrown

darkgrey

Grain sizeThe grain size scale suggested follows

the conventional engineering scheme, buthas been modified for medium grainedrocks (Table III).

Skeletal, oolitic and detrital carbonatesare predominantly medium grained, andconsiderable advantage would be ob-tained by the use of the subgradesF, M, C in brackets referring to a pre-dominant grain size of fine, medium orcoarse sand grade.Structure

The structure of a carbonate is ofutmost importance to its engineering per-formance, particularly where the less in-durated skeletal oolitic or detrital carbon-ates are involved. The terms recom-mended by the Working Parties cover thedescription of the structure of the rock,but reference to cross-stratification or thepresence of stromatolites (algal struc-tures) may give further indications of themanner in which the rock can fail.Discontinuities

These include all fractures within the

rock or soil, e.g. joints, fissures, faults,cleavages, etc., and their description andrecording are essential. Table III showsthe recommended terminology and sizeclassifications.Weathering

The terms recommended by the twoWorking Parties to describe the degreeof weathering are summarised in Table IV.It should be pointed out that these scaleswere developed from experience in tem-perate climates, and although applicableto weathering in humid tropical climates,they may not be suitable to weatheringin a hot dry climate. In an arid environ-ment, where many of the younger car-bonates occur, there is very little move-ment of water through the rock mass ex-cept at or near the surface. Weatheringtherefore tends to produce only a thinmantle of waste and involves complexchemical processes, often resulting in sur-face hardening of the rock, and the con-centration of aggressive chemicals.

Another feature peculiar to the carbon-ate suite of rocks is that the weatheringprocess does not necessarily involve thestraightforward disintegration of rockinto a soil, but the solution of the rock,producing voids and karstic surfaces, witha thin soil of insoluble residue.Cementation and compaction

These terms are reasonably synonymousfor both rocks and soils and their descrip-tion is difficult but should be included ifeven on the qualitative basis as shownbelow:

Well cemented (with quartz/calcite?)Moderately cemented (with calcite/

quartz?)Poorly cemented (with clay/calcite?)Non cementedIndurated

TABLE I. LEIGHTON at PENDEXTER'S TEXTURAL CLASSIFICATION OF LIMESTONES

Grain'ienle

ratioGrains

Detrital Skeletal

Grain type

Pellets Lumps CoatedGrains

Organicframebui(dere

No organicframehui(dere

91 -- 90

DetritalLst

SkeletalLst

Pellet.Lst

Lump-Lst

Oo)itic Lst Cora()ine LstPiso(itic Lst Algal LstAlgal encr Lst etc

OUART 2 CLAV

Fig. 3. Fookes and Higginbottom (1975)—classification of impure carbonatesaccording to composition

50

1'9 -- 10

DetritalMicriticLst

M icritic.DetritalLSI

SkeletalM icriticLst

M I cII \ I c.SkeletalLst

Pellet-M icriticLst

M icriticPelletLst

Lump.MicnticLst

Micntic.LumpLst

Oo(itic(Pisa(itic etc)-MicriticLst

M <critic.oo(itic(Pisohtic etc)Lst

Coralline.micritic, LstAlgal micriticLst etc

M i C I' t I C.

cora)(ine.M icritic.a(ga(Lst etc

100 90Per cent calcite

50 10 0

Micritic Limestone

C0

E

E 0Jl0

0'o(omiticLimestonr.

Calcitic

DolomiteE00cs

TABLE II. FOOKES 81 HIGGINBOTTOM'S ENGINEERING CLASSIFICATION OFCARBONATES (established alternative names are in brackets)

P,irtic<ilate carbonate r)eoosits (increasing grain size)Non particulateor massive rar-hon,ite <I<'Iiosi<5

0 10 50 90 100Per cent dolomite

(a) Pettilohn's classification of calcite dolomite mixtures.

Volume percentof rock

DetailedClassification

StandardClassification

Traces —2 vo( % Extremely slightly do(omitic

2 —5 vol % Very slightly do(omitic

5 —10 vo(% Slightly do(omitic

10 —25 vo(% Fairly do(amitie

25 —50 vo(% Highly do(amitieDo(omitic

(bl Schmidt's detailed classification of calcite-dolomite mixtures.

Fig. 4. Classification of limestone-dolomitemixtures

42 Ground Engineering

0 '0

00a0)

B 00<C

I

0

u

CARBONATE SAND

/'Biorlastic Oolite

CARBONATE GRAVELE

CARBONATE E

ISUO 80„,N,H,/ K„,NCARBONATE

S I LTC) <1<x(

(0<gJn<C)san<I

(I<10ICJ<l<C)gravel

( 0Iis 'I <1 I C )

<ur,ive(

(0I' 0 I110 i

gravel( 0I (g 0 i< I C )

gravel( Inc<<i I <1 IC)

CARBONATESILTSTONEor CHALK

CARBONATESANDSTONE

or CALCARENITEBloc)Jr<le 00)iteC Sst or C Sst orCalcaremte CalcareniteImicrocouuina)

CARBONATE CONGLOMERATEior Breccia if Jivgulari (CJ(erudite)

CARBONATEMUOSTONE

( ca Ic i I u t i t e ) I / i L(ca)cisiltite) Shell Conglt Coral Cong(< Algal Pisolite Conglt

or Breccia or Breccia Cong(t or Breccia(co<iuma) or Breccia

DETRITAL LIMESTONE

/'Bine(astic 00(iticLimestone Limes<one

A/FINE GRAINED LIMESTONE

CRYSTALLINE LIMESTONE OR MARBLE(ten<la towards uniformity of gra n size and loss of on<gina( textiirc)

No unin<luraieil<epic<<I<i I J I ives

dcs

d ul

d ZOOW 0)a <Il

du<C 0)Ow<0 ic

TABLE III. SIZE, SPACING, DENSITY AND PLASTICITY CLASSIFICATIONS

Soil ik Rock DiscontinuitySpacing Descriptions

Extremely Very Mod,Narrow Narrow

VeryWide

Bedding SpacingDescriptions

ThinlyLaminated

Thickly VeryLaminated Thin Th'n Medium Thick Very

Thick

Rock Grain SizeDescriptions

VeryFine Fine Medium Coarse Very Coarse

Soil ParticleSize Divisions

Sand G rave I

C I ay CobblesF ~Md ~c F ~Mdi ~c r

~

Md ~cBoulders

mm 0.002 0.006 0.02 0,06 0 2 0.6 2 6 20 60 200 600 2000

Diameter or Spacing

Relative Densityof Granular Soils Blows

15Very Loose

4Loose 35 65

Medium Dense10 30

Dense Relative DensityVery Dense

50 N Values

Plasticity F ieldEstimate

Lean Intermediate Fat Very Fat Extra Fat

Descriptions LaboratoryTerm

Low Intermediate High Very High Extra High

Liquid Limit, /, 20 35 50 70 90 Liquid Limit, '/0

TABLE IV. WEATHERING CLASSIFICATION

Diagnostic Features

Soil Mass

TermGradeSymbol

GradeSy mbo I

Term

ResidualSoil

Rock Mass

Diagnostic Features

Rock is discoloured and completely changedto a soil in which original rock fabric iscompletely destroyed.

Soil discoloured and totally altered,with no trace of original structures.

CompletelyWeathered WV Completely

Weathered

Rock is discoloured and changed to a soilbut original fabric is mainly preserved.Occasional small corestones.

Soil mainly altered with occasionalsmall lith orelics of original soil.Little or no trace of original structures.

HighlyWeathered

HighlyWeathered

Rock is discoloured; discontinuities may beopen and surfaces discoloured. Originalrock fabric near discontinuities may bealtered and penetrate deeply inwards butcorestones are still present.

Soil composed of large discolouredlithorelics or original soilseparated by altered material.Alteration penetrates inwards fromdiscontinuities.

Moderately W I I I W I I IModerately

Weathered Weathered

Rock is discoloured; discontinuities may beopen and will have discoloured surfaces withalteration starting to penetrate inwards.Intact rock noticeably weaker than fresh rock.

Material composed of angular blocksof fresh soil which may or may notbe discoloured. Some alterationstarting to penetrate inwards fromdiscontinuities separating blocks.

Parent soil shows no discolouration.or loss of strength. Discontinuitiesusually tight and not discoloured.

S I igh tl yWeathered

Fresh

W II W II Weathered

FaintlyWeathered

W I W IA Fresh

Rock may be slightly discoloured, particularlyadjacent to discontinuities, whicn may be openand will have slightly discoloured surfaces.Rock not noticeably weaker than fresh rock.

Weathering limited to the surfaces of majordiscontinuities.

Parent rock shows no discolouration or lossof strength. Discontinuities usually tightand not discoloured.

ConchoidalfractureWater worn or dueto fracture of lam-inated or finegrained rockFracture showingmore or less uni-form roundedgrainsRough fracture offine or medium

2 Smooth

3 Granular

4 Rough

Texture and particie shapeTexture applies to the appearance of

a naturally occurring (e.g. gravel) orartificially formed (e.g. crushed rock)material surface and several groups arerecognised. This portion of the descriptionis especially important if the materialsinvolved are to be used in the aggregateindustry. Recommended groups are asfollows:Group Surface Characteristics

texture1 Glassy

5 Crystalline

5 Honey-combed

grained rock con-taining no visiblecrystalline constit-uentsContaining easilyvisible crystallineconstituentsWith visible poresor cavities

Particle shape applies primarily to nat-urally occurring granular soils (sands,gravels, etc.) but can also be used todescribe crushed rock chipping character-istics. Recommended terminology is asfollows:

RoundedIrregularAngularFlakyElongated

Estimated mechanical strengthThe categories, terminology and field

definitions of soil and rock strengths are

given in Table VMinor lithological characteristics

These should immediately prefix themain soil or rock name and preferably besimple, common and accurate.Soils

In the case of soils, grading and plas-ticity characteristics are noted. In the for-mer group a choice of poorly graded,uniformly graded, gap graded and wellgraded is possible. Regarding plasticity,reference is made to the lower portion ofTable III for the choice of categories.Rocks

In the case of rocks a proposed tex-tural/min'or lithological classification isgiven in Table Vl. This is based on botha grain type and grain/micrite (non cry-stalline) ratio.Main nameSoils

The choice of the main soil name isgoverned by the soil particle size nomen-clature of the major soil constituent. Thus,

March, 1979 45

TABLE V. STRENGTH CLASSIFICATION

FieldDefinition

Extrudesbetweenfingerswhensqueezed

Veryeasilymouldedwithfingers

Moderatefingerpressurerequiredto mould

Mouldedonly bystrongfingerpressure

Cannotbemouldedwithfingers

Brittleor verytough

Crumblesin hand

Thinslabsbreakeasilyin hand

Thinslabsbrokenbyheavyhandpressure

Lumps orcorebrokenby lighthammerblows

Lumps orcorebrokenby heavyhammerbl ows

Lumps onlychip byheavyhammerblows. Dullringingsound

Rocks ringon hammerblow.Sparks fly

Description Verysoft

Soft Firm Stiff Very HardStiff Weak

WeakModer-atelyWeak

Moder-atelyStrong

Strong VeryStrong

ExtremelyStrong

StrengthCategories

18 36 72 144 288Shear Strengths of Clays (kN/msl +

1,25 5 12.5 50 100Unconfined compressive Strengths of Rocks (MN/mz)

200

Point Load Strengths of Rocks (MN/mz)

0.075 0.3 0.75 3 6 12

Based on the approximate relation: —Comp. Strength = 16 Point Load Comp. Strength+ Various published strength categories exist —quote reference used

TABLE VI. PROPOSED TEXTURAL CLASSIFICATION OFCARBONATES

TABLE VII. DIAGNOSIS OF CARBONATE TYPES WITHDILUTE HYDROCHLORIC ACID

(Test comprises immersing rock chips about ) in dia x f in thick in colddilute acid)

Containing Micrite matrix

Matrix supportedGrainsupported

Gramsupported—lackingmicritematrix

Depositional texture recognisable

Originalcomponentsboundtogether

Depositionaltexturenotrecognisable

Rock Type

Limestone

Dolomitic Limestone

Reaction with cold dilute HCL ll nn10)

Violent effervescence, frothy audible reaction, small chips will bob aboutand tend to float on the surface

Bosk, quiet effervescence; small chips skid about on the bottom of thecontainer and rise slightly off the bottom; there is a continuous stream ofCO. through the acid

Less than10% grains

MlcrilicLimestone

More than10% grains

Micritic—0oliti c,Skeletal,Shelly, orDetritalLimestone

colitic,Skeletal,Shelly, orDetrital-micriticLimestone

Oolitic,Skeletal,Shelly, orDetritalLimestone

A I ga I,Coralline,etc.Limestone

Crystalline

LimestoneCalcitic Dolomite

Dolomite

Mild emission of CO. beads, small specimens may wbrate, but tend to slay inone place.

No effervescence; no immediate reaction, slow formation of CO, beads onthe surface of the rock, reaction slowly accelerates until a thin stream ofbeads rises to the surface, especially when heated.

as shown in Table III, the s'oil name canrange through clay, silt, sand, gravel, cob-bles or boulders. The sand and gravelranges may be further subdivided intocoarse, medium or fine categories. Sub-ordinate amounts of a size other thanthat indicated by the soil name may beindicated as follows:

Clean: sands and gravels with 0-5% infine fraction

With some: with 5-20% of a specifiedparticle size

Silty, Clayey: with 20-50% of finematerialGravelly, Sandy: with 20-50% of coarse

materialRock

The selection of the correct main rockname for the carbonate suite of sedimentsis not easy and is based on both thequantity and form of the carbonate con-stituents as well as the presence and typeof various "contaminant" materials.

The first step in establishing the namelies in determining, by careful detailedexamination using a hand lens and cor-roborated, if necessary, by microscope orby 'laboratory testing, the proportion ofcarbonate to non-carbonate material. Thisthus establishes the vertical position ofthe material concerned in Fig. 5. Use ofan acid reaction test is also helpful in thisrespect and Table Vll defines this test.

The next step involves the use of stain-ing and etching procedures in the firstinstance to establish the proportion ofdolomite in the carbonate-rich rock. Thisproportion can again be subsequentlyconfirmed by microscopic or laboratorytechniques and defines the horizontal lo-cation of the material on Fig. 5.

The final step in establishing the cor-rect "pigeon-hole" for the rock necessi-tates the determination of the major andpossibly minor grain size categories ofthe lyon-carbonate constituents. This is car-ried out again by careful inspection of

46 Ground Engineering

the sample using a hand lens or micro-scope.

The full and correct main name is thusdetermined.

Examples of descriptionsIf a project involves the logging of a

great many carbonate suite samples, priorto an extensive testing programme, forinstance, a standardised pro forms des-cription sheet as shown in Fig. 6 couldbe effectively used for both soils androcks.

Examples of the use of such a sheet in

Iooaf

0%/

[ 0% Increasing detrital CLAY content

increasing detrital SILT and SAND contentltOO:; =

CLA YSTONE w thsome s I i/sand

20 i 5

SILTSTONE or SILT or SANDSTONESANDSTONE with some clay

20CLAY orSHALE

(m 550

Clayey SILT cr Sandstone Siitv or san<IT CLAYSTONE / j / /5 5

or SANDSTONEh somea or I mes to e

SIIIY OI s

CLAYSTw ih so

I mesicne c

Doiom ie ocalcareousclayey SILTSANDSTONE

Calca aouis ity sandyor clayey

DOLOMITE

Caica cour cdolcm ie

s fit o sandyCLAYSTONE

Doiom iei Ity, sandyor clayey

LIMESTONE

cU

lic0U c

uxl cc 0o

UC0 p

iotn IL

xtpsaC

Uipo UcgaUc

us DOLOfitiTEh some

and 0 clay

/5

/ Caica cour DOLOMITEI

DOLOMITE 10 20 50

Doiom te LIMw th som

s Ii, sa sii a

Doiam ie LIMESTONE

20 10LIMESTONE

Iioo.- =

Increasmg LIMESTONE content

Increasing DOLOMITE content

ioohl

Fig. 5. Proposed classification of pure and admixtures of carbonate rocks

(Name of company) SAMPLEDESCRIPTION

SHEET

LOGGED BY

DATE

SHEET of

HOLE/PIT

LOCATION

GROUND LEVEL

3 4 r SOIL

Hue

Value

P> Chroma

V Fine ( .002mm

Fine .002—.06

Med .06—2

Coarse 2—60

V Coarse )60

Xalline~

GranularI-Amorphoussc

Porousj

Rough

Smooth j Glassy

Oz V Thick )2m

0 Med 2-.020V Thin (.02

Ui V Wide )2mI-Z Mod 2—.020

Close ( .02

0 Well

Mod

Poorly

o Friable j Non

Weathering FSMHCR

V Weak

Weak

Mod Weak

K Mod StrongI-

Strong

$4te Dork

yclloo

srovo grey

Calcite

F H

Cre col

Calc tc

C~yShgkt

Chroma

Indurated

Non Cemented

Poorly Cemented

Mod Cemented

Well Cemented

V Dense~

Hard

Dense~

Stiff

Med Dnse~ Firm

Loose~

Sof t

V Loose j V Soft

Homogeneous

Layered

Fissured

Laminated

Weathering FSMHCR

Rounded

Irregular

Flakey

Angular

Elongated

Glassy

Smooth

Granular

Rough~

Crust

Xal line

Pole Hue

srouo green Value

K

000Z0ts

00

K

tgZK

K

0K

lUtsKsoiU

gK

o.

sciUI-iU

gK

Coral

M ic ritic

Clayey j

Cicreous

Lmestne

Claystne

Sitstne

Algal

Xall inc

Silty[

Sandy

Dl omi tie

Dlomite

Shale

Sandstne

V Strong

Detrital Shelly

oolitic Pisolitic

2 I

JJu'tz.

Se,ruo

Honeycombed

Well G raded

Gap Graded

Uniform Graded

Poorly Graded

Clean

Clayey Silty

Sandy

Lean

Detrital

Gr veil y

In trmd

Xall inc

Shelly Coral

Qtz Cele

Clay Silt

Sand Gravel

Zofcg

Fat Z0CC

Dol

With Some

Remarksore as

5mm

ClayFi/ledCoviti'es

Trc cloy

Orcus.

lccm

Round

Clayst.Nods.

With Some

Remarks

Fig. 6, A suggested standardised sample description sheet

describing samples 1, 2, 3 and 4 as sum-marised on this figure are as follows:Full description of Rock Samp/e 1

Pale yellowish brown medium grainedgranular textured massive bedded intact(unjointed) moderately calcite cementedfresh moderately strong micritic/detritalsilty dolomitic LIMESTONE showing oc-casional 5mm diameter clay-filled cavities.Full description of Rock Samp/e 2

Dark grey very fine grained rough tex-tured laminated widely jointed non-cemented highly weathered weak mictriccalcareous CLAYSTONE with some silt.Full description of Soil Samp/e 3

Brownish cream poorly calcite cement-

48 Ground Engineering

ed homogeneous rounded smooth poorlygraded sandy (quartz) crystalline quart-zose (50%) and calcareous (50%) GRA-VEL with traces of clay.Full description of Soil Samp/e d

Pale greenish grey slightly induratedfirm to stiff laminated fissured slightlyweathered silty intermediate calcareousCLAY. Occasional 10cm diameter roundedclaystone nodules.

ReferencesAnon (1970): "The logging of rock cores forengineering purposes". Quart. Jnl. Eng Geol., Vol3, no. 1 pp. 1-24.Anon (1972): "The preparation of maps andplans in terms of engineering geology''. Q. Jnl.Engng. Geol. Vol. 5 no. 4. 295-382.Dunham, R. J. (1962): ''Classification of carbon-

ate rock according to their texture". Jn: W. E.Ham (Editor), Classification of Carbonate Rocks.Am. Assoc. Petrol Geologists. Mem 1: 108-121.Folk, R L. (1959); "Practical petrographic classi-fication of limestone". Bull. Am Assoc. Petrol.Geologists, 43; 1-38.Folk, R. L. (1962): "Spectral subdivision of lime-stone types''. Jn; W. E. Ham (Editor), Classifi-cation of Carbonate Rocks. Am. Assoc. Petrol.Geologists, Mem 62-85Fookes, P. G. 8, Higginbotrom, I. E. (1975): "Theclassification and description of near-shore car-bonate sediments for engineering purposes". Geo-technique, Vol. 25, No. 2: 406-411.Leighron, M. W. & Pendexter, C, (1962): "Car-bonate Rock Types". Jn. W. E. Ham (Editor)Classification of Carbonate Rocks Am. Assoc.Petrol. Geologists. Mem. 1: 62-85.Petti/ohn, F. J. (1956): Sedimentary Rocks, 2 ed.Harper and Bros., New York, N, Y. 718 pp.Geological Society of America 1963. Rock ColorChart.Munsell Color Company Inc. 1954. Munsell SoilColor Charts, Baltimore (Munsell Color Co. Inc.)