31. PLASTICITY CHARACTERISTICS OF THE QUATERNARY SEDIMENTS OF THEGUATEMALAN CONTINENTAL SLOPE, MIDDLE AMERICA TRENCH, AND

COCOS PLATE—LEG 67, DEEP SEA DRILLING PROJECT1

Richard W. Faas, Department of Geology, Lafayette College, Easton, Pennsylvania

ABSTRACT

The plasticity characteristics of the Quaternary sediments of the Guatemalan continental margin were determinedfrom five sites drilled during Leg 67 of the Deep Sea Drilling Project. The 64 samples analyzed are from various marineenvironments, including the Cocos Plate, Middle America Trench, and the trench lower slope to midslope of theGuatemalan continental slope. The sediments are primarily hemipelagic muds and trench-fill turbidites and includequantities of siliceous and calcareous biogenic components.

The sediments are generally classified as organic clays of medium to high plasticity, containing micaceous sands andsilts, with 14% classed as inorganic clays of medium to high plasticity.

High sedimentation rates in Quaternary sediments are the result, in part, of sediment gravity flows that dependupon rheological properties, i.e., sediment plasticity. Mudflows and cohesive debris flows appear to be significantdownslope transport mechanisms in these highly plastic sediments.

INTRODUCTION

As more interest is focused on active continental mar-gins and their deposits, it is inferred that many of theseare areas of downslope sediment transport. Such trans-port may be rapid and episodic, it may be slow and per-vasive; or it may be some combination of the two. Lowe(1979) has indicated the importance of rheology in dis-tinguishing the mass transport mechanisms as fluidalflows or debris flows by their fluid and plastic behavior,respectively. Insofar as this concept has validity, the ex-pected rheological behavior of the sediments accumulat-ing on any particular continental margin should be as-sessed before any specific process is studied in depth. Ameasurement of the rheological characteristics of conti-nental margin sediments is readily available in the formof the Atterberg limits.

The purpose of this paper is to present the plasticitycharacteristics of the Quaternary sediments from theGuatemalan continental margin at each of the Leg 67sites (excluding Sites 498 and 500) (Fig. 1) and to suggestthat these characteristics may be useful in predicting theform of downslope mass transport that may be or mayhave been operating. The data consist of shipboard mea-surements of initial water content and Atterberg limits.Laboratory analysis of particle size distribution of thesediment from the same samples enabled a determina-tion of the "activity" of the sediments.

Atterberg LimitsAtterberg limits (Casagrande, 1948) are based on the

concept that a soil is a two-phase system composed ofsediment particles and water. The rheological behavior

state of such a mixture changes from fluid to plastic tosolid as the mixture loses water. The point at which asediment-water mixture ceases to behave as a liquid isits liquid limit (vvL). Similarly, plastic behavior of sucha system ceases at its plastic limit (wP) and it passesthrough a semisolid state, determined by its shrinkagelimit (vvs). Each limit is the empirical measure of thewater content of the soil at that point where its behaviorchanges from one state to another. The plasticity indexilp) is a measure of the range of water content throughwhich the sediment exhibits plastic behavior:

IP = wL - wP

The liquidity index (JL) allows the natural water contentof a soil-water system to be compared directly with itsAtterberg limits and can be used to predict the consoli-dation state of a sedimentary section (Skempton, 1970).It is defined as:

= w-wP

Aubouin, J., von Huene, R., et al., Init. Repts. DSDP, 67: Washington (U.S. Govt.Printing Office).

where: w = initial water content, wP - plastic limit, andIP = plasticity index.

Plasticity CharacteristicsThrough the determination of its Atterberg limits, a

sediment can be described and classified into various de-grees of high, medium, and low plasticity. This classifi-cation, developed by Casagrande (1948), utilizes the re-lationship between the liquid limit (wL) and the plasti-city index (7P) of a sample to determine its position with-in the total range of plastic behavior. The A-line in Fig-ure 2 is an empirical boundary separating inorganicclays (above the line) and organic clays and inorganicsilts (below the line).

639

R. W. FAAS

14° 0091° 00' 90° 00'

13° 00'

San JoséGUATEMALA

Shelf

Figure 1. Location map—Leg 67 Sites.

Keller, Lambert, and Bennett (1979) utilized thistechnique to map the continental slope deposits betweenthe Hydrographer Canyon and Cape Hatteras into fourgroups of sediment with increasing plasticity. Davie,Fenske, and Serocki (1978) show the variation in plasti-city for different sediment types, including calcareousand siliceous oozes, clay, and volcanic ash from 89continental margin locations. And Richards and Fager(1980) present data on the plasticity of pelagic clays andradiolarian clay and ooze from the Hatteras AbyssalPlain.

Activity

Skempton (1953) found that the relationship betweenthe plasticity index and the clay fraction (% less than 2µm) of any particular combination of clay minerals re-mained essentially constant. Each mixture of clay min-erals can therefore be characterized by a single param-eter. This he called "activity," defined as:

Activity (Ac) = Plasticity IndexClay fraction (°7o less than 2 µm)

640

PLASTICITY CHARACTERISTICS OF QUATERNARY SEDIMENTS

140

120 -

100 -

80 -

« 60 -

40 -

20 -

10

_

Inorganic clays of medium tohigh plasticity (CH)

D

S H Δ/ " ‰ • •

>/̂ A£ Λ

>^Δ

/S Δ

i i i i

So

/o

Δ•/> ^ o

^ Q oo

D OOD

•

Organic clays of medium tohigh plasticity and micaceousor diatomaceous fine sandsand silts (OH)• - 494 and 494AO-495B-496D-497Δ-499

10 20 40 60 80 100 120 140 160 180 200

Liquid Limit (%)

Figure 2. Casagrande Plasticity Chart showing plasticity characteristics of all samples analyzed. (TheA-line is an empirical boundary separating inorganic clays from organic clays and inorganic silts. Theplasticity index and liquid limit values are based on % dry wt. of sediment; consequently it is possibleto have values greater than 100%—indeed, it is expected.)

Activity represents the surface activity of the clayfraction, such as the increased ion exchange capacityand absorption of water with decreased grain size. Ac-tivity of pure clays increases from a low of 0.23 (musco-vite) to a high of 6.0 (Na-montmorillonite). Clays aresaid to be "inactive" (Ac < 0.75), "normal" (Ac, 0.75-1.25), and "active" (Ac > 1.25).

ANALYTICAL PROCEDURE

Testing of the samples for their Atterberg limits was performed onboard the Glomar Challenger immediately after the cores were sam-pled. A sample was placed in a preweighed aluminum moisture dish,weighed on a triple-beam balance, and placed in a drying oven at110°C for drying overnight. Upon removal from the oven, the samplewas immediately reweighed and water loss determined. At the sametime, liquid limits were determined. Half of the sample was taken todetermine its water content; the other half was used for plastic limitanalysis.

Liquid limits were determined according to the simplified pro-cedure described by Lambe (1951) and calculated as follows:

WL = f)°where wN = the water content of the sediment sample and N = thenumber of drops of a standard liquid limit cup required to close thegroove in the sediment sample. Values of liquid limit (Table 1) repre-sent an average of three separate determinations of the same sample.

Samples were also taken for analysis of organic carbon contentand particle size distribution. Some of the carbon analyses were per-formed on ship, others were done later at the University of Oklahomalaboratory. All were analyzed in a Leco combustion apparatus. Grainsize analysis was done at the DSDP laboratory in La Jolla.

Quaternary Sediments

The mantle of Quaternary, hemipelagic mud of theGuatemalan continental margin thins seaward and con-tains significant quantities of siliceous and calcareousfossil remains. Sediment thickness varies from greaterthan 200 meters at Site 496 on the upper trench slope toapproximately 100 meters at Site 498 on the lower trenchslope. Within the Middle America Trench the thick-ness of Quaternary sediments is variable, ranging fromabout 80 meters (Site 500) to 120 meters (Site 499).These sediments are interbedded pelagic diatomaceousmuds and fine sand, and muddy turbidites. Quaternarysediments are only about 60 meters thick at Site 495 onthe oceanic plate and are composed of diatomaceoushemipelagic muds. Sedimentation rates vary from 300m/m.y. in the trench (Site 499) to 37 m/m.y. on the oce-anic plate (Site 495). As expected, the greatest sedimentaccumulation occurs in the trench, because it is the ulti-mate resting place for sediment transferred from higherelevations on the slope. Dominant clay minerals are il-lite, montmorillonite, and kaolinite. The latter two aremost abundant (Heinemann, this volume). Illite is miss-ing from Site 495 on the ocean plate.

Organic carbon contents of the samples ranged from0.62% to 3.59%, averaging 2.00% (s = 0.62%, n = 52).

The data in Table 1 indicate that the majority of thesediments analyzed are classified as "organic clays ofmedium to high plasticity, containing micaceous sandsand silts" (OH soils, as defined by the Unified Soil Clas-

641

R. W. FAAS

Table 1. Summary of sediment properties (Atterberg limits, initial water content, particle size analysis, and activity ofsamples analyzed).

Sample(interval in cm)

Hole 494

1-1, 133-1351-3, 109-1111-5, 69-712-3, 103-1052-6, 119-1213-3, 99-1013-6, 118-1204-4, 77-79

Mean (x)Std. Dev. (s)

Hole 494A

1-1, 102-1041-3, 70-722-7, 37-395-1, 40-42

Mean (x)Std. Dev. (s)

Hole 495

3-1, 67-703-3, 115-1173-6, 132-1344-3, 140-1434-5, 63-665-1, 17-215-3, 128-1325-5, 127-1316-4, 59-63

Mean (x)Std. Dev. (s)

Hole 496

1-1, 96-992-1, 130-1325-6, 129-1316-5, 110-1128-1, 70-749-5, 80-8410-5, 80-8412-5, 20-2513-3, 60-6214-2, 100-10216-1, 120-12217-1, 80-8219-3, 75-7820-2, 102-10421-6, 138-14022-6, 100-102

Mean (x)Std. Dev. (s)

Hole 497

1-1, 98-1022-1, 138-1403-3, 60-644-1, 110-1125-3, 80-846-1,40-427-4, 100-1029-3, 80-8210-4, 30-3212-6, 76-7813-3, 93-10014-3, 63-6516-8, 30-32

Mean (x)Std. Dev. (s)

Hole 499

1-1, 138-14024, 78-803-4, 98-1025-5, 138-1406-4, 28-307-2, 70-729,CC, 10-12

12-3, 130-13214-3, 18-2015-2, 138-14217-3, 60-6219-4, 82-84

Mean (x)Std. Dev. (s)

Sub-bottomDepth(m)

1.304.106.70

12.0416.7052.5027.2033.25

1.003.70

17.9038.40

19.7023.1627.8332.9235.1338.1742.3045.3052.61

0.9810.8146.8052.6165.2280.8290.32

108.72115.61124.01141.71150.81172.76181.03196.89206.01

1.018.39

20.1227.1140.3245.4165.0177.3187.81

110.27115.50124.64150.81

1.396.79

16.0136.8943.7950.7176.11

100.31118.19127.40138.11167.83

wL

127.1117.8113.0116.776.3

121.4117.7138.7

116.117.9

111.6113.4108.898.1

107.96.8

113.5165.8117.5171.5178.9151.3135.2166.7147.2

156.421.7

127.8126.2142.6118.7145.0112.6108.4139.9130.5106.5136.2117.7124.2129.2118.4123.2

125.411.6

113.5132.4126.4112.9104.4124.9100.4111.2145.7123.7112.2137.9149.9

122.715.5

63.5130.1117.3105.880.9

110.274.3

143.9120.1125.9125.6142.2

111.626.1

Atterberg Limits

wp

45.956.650.048.556.454.757.363.3

54.15.6

56.656.659.153.7

56.52.2

52.788.084.081.078.380.765.385.178.1

77.011.2

52.962.372.357.549.846.455.464.460.156.974,257.967.349.758.158.9

59.07.8

40.448.638.743.239.552.554.956.370.072.057.169.966.6

54.612.2

38.458.751.351.039.351.236.7

70.758.970.771.649.0

53.912.5

81.261.263.068.219.966.760.475.4

62.018.5

55.056.849.844.4

51.55.6

60.877.893.5

101.9109.670.669.981.669.1

81.616.6

74.963.970.361.195.266.253.175.470.449.861.959.856.979.560.364.4

66.411.2

73.183.887.669.764.972.445.454.975.751.755.067.883.4

68.113.2

25.171.4

66.054.841.658.937.6

73.261.255.254.193.2

57.717.9

0.770.491.100.820.590.550.520.37

0.650.23

0.520.400.460.16

0.390.16

0.601.120.740.670.631.021.190.780.89

0.850.22

1.180.610.540.550.550.870.640.830.490.600.250.550.330.500.360.44

0.580.23

1.391.050.841.000.940.760.660.740.350.610.580.380.36

0.740.30

1.250.970.800.731.290.641.22

0.320.400.560.720.58

0.790.33

H'

108.486.6

100.0104.668.291.288.691.1

92.312.5

85.079.364.246.5

68.817.2

89.5175.4153.3149.0148.9152.588.7

148.7139.5

138.429.5

141.2101.0110.890.9

102.0104.489.489.594.686.289.490.986.289.779.987.0

95.814.5

142.4136.5112.3112.9100.3107.385.196.896.5

103.5112.795.796.3

107.616.4

69.9128.0104.291.093.189.082.6

93.983.6

102.6110.7102.8

95.915.0

Sand

3.40.8

15.511.312.78.7

11.90.7

8.15.7

5.1

0.41.8

2.42.4

3.51.10.40.70.61,82.42.03.8

1.81.2

1.50.4

0.8

0.61.62.24.12.1

1.71.2

4.52.62.51.71.72.9

1.91.83.01.91.2

2.30.9

0.53.20.65.6

16.84.0

22.3

1.60.92.71.5

5.47.3

Size Ana

Silt

47.636.941.841.545.946.146.340.1

43.33.8

53.6

38.646.0

46.17.5

57.924.837.027.331.339.837.240.353.1

38.710.9

56.542.8

48.2

92.859.248.455.949.7

56.715.5

46.750.964.556.450.756.3

54.847.253.452.147.4

52.85.2

70.155.776.456.643.463.442.9

53.138.444.534.6

52.613.4

Clay

49.062.442.747.141.445.241.859.2

48.68.0

41.3

61.052.2

51.59.9

38.674.162.671.968.158.460.457.743.1

59.412.0

42.056.8

51.0

6.539.249.440.048.3

43.816.3

48.846.533.042.047.740.7

43.351.143.646.051.4

44.95.3

29.441.223.037.839.832.634.8

45.460.752.863.8

41.912.8

lysis

Classification

Silty claySilty claySilty claySilty clayClayey siltClayey siltClayey siltSilty clay

Clayey silt

Silty claySilty clay

Clayey siltSilty claySilty ciaySilty claySilty claySilty claySilty claySilty clayClayey silt

Clayey siltSilty clay

Silty clay

SiltClayey siltSilty clayClayey siltClayey silt

Silty clayClayey siltClayey siltClayey siltClayey siltClayey silt

Clayey siltSilty clayClayey siltClayey siltSilty clay

Clayey siltClayey siltSiltClayey siltClayey siltClayey siltSand-silt-clay

Clayey siltSilty claySilty claySilty clay

Ac

1.660.981.471.450.481.471.441.27

1.280.38

1.33

0.820.85

1.000.29

1.571.051.491.421.611.211.161.411.60

1.390.21

1.45!.68

1.48

9.521.521.151.981.25

2.502.85

1.491.802.651.661.361.78

1.741.011.261.471.62

1.620.42

0.851.732.871.451.041.811.08

1.350.911.021.46

1.420.58

Activ ty

Classification

ActiveNormalActiveActiveInactiveActiveActiveActive

Active

NormalNormal

ActiveNoActActActNoNoActAct

mallveive

ivemalmaliveive

ActiveActive

Active

ActiveActiveNormalAct veActive

ActiveActiveActiveActiveActiveActive

ActiveNormalActiveActiveActive

NormalAct veAct veActiveNormalActiveNormal

ActiveNormalNormalActive

Plasticity

CHOHOHOHOHOHOHOH

OHOHOHOH

OHOHOHOHOHOHOHOHOH

OHOHOHOHCHOHOHOHOHOHOHOHOHOHOHOH

CHCHCHCHCHOHOHOHOHOHOHOHOH

OH

OHOHOHOHOHOH

OHOHOHOHCH

oc%

2.541.652.252.121.432.322.422.77

2.19

0.45

2.272.122.151.93

2.120.14

0.620.762.13

—1.150.860.891.451.22

1.140.48

2.82——

1.942.502.471.832.50

—1.953.592.352.383.092.202.06

2.440.50

2.572.922.191.852.202.63

—1.672.112.322.44

—1.01

2.17

0.52

1.07

2.391.941.881.391.271.95

2.321.951.321.431.16

1.67

0 45α. Dev. (s) 26.1 lz.5 w.y u.a n.v i.i ii.t iz.β u.z>β u -

te: Symbols: w = initial water content (% dry weight); H X = liquid limit; wp plastic limit; lp = plasticity index; //_ = liquidity index; Ac = activity; CH =inorganic clays of medium to high plasticity; O H organic clays of medium to high plasticity containing micaceous sands and silts; and OC/o = percentageof organic carbon.

642

PLASTICITY CHARACTERISTICS OF QUATERNARY SEDIMENTS

sification, Wagner, 1957). Only eight samples, 14% ofthe total number analyzed, plotted above the A-line(Fig. 2), and those are classified as "inorganic clays ofmedium to high plasticity" (CH soils, as defined by theUnified Soil Classification).

One might question the appropriateness of the Uni-fied Soil Classification for classifying submarine sedi-ments in view of the fact that it was developed specific-ally to classify terrestrial soils on the basis of their engi-neering characteristics. Application of this classificationsystem may not be as inappropriate as may seem at firstglance, inasmuch as many present-day terrestrial soilsformed initially as marine deposits, and many others aresecondarily derived from marine sediments. Moreover,classification on the basis of plasticity characteristicsappears justifiable, because this property also relates tovarious mass transport mechanisms.

Figure 2 shows the position of each sample analyzedon the Casagrande Plasticity Chart. It is evident thatthose defined as "inorganic clays of medium to highplasticity" are primarily from Site 497, and Table 1 indi-cates that these sediments comprise a layer extending toa depth of 40.0 meters. No obvious textural or lithologicdifference was observed in the cores taken below thisdepth.

Figure 3 shows the activity of the Guatemalan sam-ples. All but one are considered to be either "normal"(15 samples) or "active" (34 samples).

Implications of Plasticity for Sediment TransportAccumulation rates of the Quaternary sediments on

the Guatemalan continental slope are quite high. At Site496, the rate is 205 m/m.y.; at Site 497, located in theMiddle American Trench at the base of the inner trenchslope wall, it is 300 m/m.y. (von Huene, Aubouin, etal., 1980). Rapid downslope transport of sediment isclearly indicated, perhaps involving a variety of pro-cesses.

Because of the high plasticity index of the Quaternarysediments, mudflows, cohesive debris flows, or cohesiveflows (defined on the basis of Bingham plastic flow be-havior by Lowe, 1979) should be particularly effectivein transferring sediment basinward.

Other mechanisms of subaqueous mass transportmay likely contribute to the high sedimentation rates.An obvious mechanism is that of episodic turbidity cur-rents, possibly generated from large-scale slumps initi-ated in the unconsolidated sediment column by tectonicevents associated with a convergent continental margin.

Low- Versus High-Latitude Plasticity CharacteristicsThat the sediments off the Guatemalan continental

margin are classified generally as OH soils (Wagner,1957) is rather unusual when compared with the dataavailable from other regions. Keller (1971), in a study of67 surface sediment samples from the Norwegian andGreenland seas, indicates that they are largely inorganicclays of medium to high plasticity (CH), sandy clays,and slightly plastic inorganic silts. Only two of the sam-ples plotted below the A-line and were classified as or-ganic clays (OH). Davie, Fenske, and Serocki (1978)

100

90

80

70

× 60V•a

δ 5 0

last

α.

40

30

20

10

n

-

•

-

I// '

/ /

/ // // / α yS

/ X/ /

/ /

o

A/

// u/ ,

d

\ :

w i

/

/

y

•

/ •

• /\ ^ /

/ AΔ /

/

• Λ<O

D Q K /

• x

/S Holes

S - 494O - 494AA-495Δ-496• - 4 9 7D - 4 9 9

ActivityInactive Wc<0.75)Normal (Ac, 0.75-1.25)Active Wc>1.25)

10 20 30 40 50Percent Clay (<2µm)

60 70 80

Figure 3. Activity chart showing activity of all samples analyzed.

show that clays generally lie above the A-line on a plasti-city chart and are classed as CH soils. Siliceous oozes liefar below the A-line and are classified as OH soils, andcalcareous oozes lie below the A-line and show low plas-ticity. Richards and Fager (1980) show that pelagic claysfrom 5600 meters in the Nares Abyssal Plain lie abovethe A-line and are classified as CH soils. On the otherhand, Keller, Lambert, and Bennett (1979) find OH sed-iments covering a broad area of the lower continentalslope of the east coast of the United States from the Wil-mington Canyon south to Cape Hatteras.

Figure 4 shows the plasticity characteristics of sedi-ment defined as terrigenous mud (T-2, JOIDES Panelon Sedimentary Petrology and Physical Properties,March 1974). These samples were taken on Leg 38 in theNorwegian-Greenland Sea and represent the author's asyet unpublished data. The sediments exhibit mediumplasticity and lie, for the most part, above the A-line(CH soils).

These sediments are composed of mixtures of mont-morillonite, illite, kaolinite, and chlorite, with mont-morillonite dominating (White, 1976). Consequently,they are not unlike the Guatemalan sediments with re-spect to clay mineral composition. However, organiccarbon content is quite low, ranging between 0.0% to1.3% (White, 1976). The Guatemalan sediments aver-age 2.00% organic carbon; therefore their plasticity be-havior appears to be significantly influenced by thiscomponent.

It is suggested that plasticity behavior of terrigenousand hemiterrigenous sediments in high-latitude regions

643

R. W. FAAS

120

100 -

80 -

- 6 0

40 -

20 -

10

-

Slightly plastic ,inorganic silts, \'

- sandy clays yf

yInorganic clays of medium to z y<high plasticity (CH) Vy'

#

^ Organic siltsand silt—clays

I i i

•

Organic clays of medium tohigh plasticity and micaceousor diatomaceous fine sandsand silts (OH)

i \ |

10 20 40 60 80 100Liquid Limit (%)

120 140 160 180

Figure 4. Casagrande Plasticity Chart showing plasticity characteristics of terrigenous (T-2) sedi-ments from Leg 38, Norwegian-Greenland Sea (author's unpublished data).

is different from that of similar sediments accumulatingin lower latitudes due to the greater amount of organ-ic carbon (and soluble by-products) produced in these re-gions and incorporated in the sediments. Exceptions willoccur (i.e., regions of upwelling), but organic mattercontent appears to be a factor in determining plasticitycharacteristics in compositionally similar sediments.

CONCLUSIONSAlthough plasticity data for comparison are still

rather limited, it is clear that the Guatemalan continen-tal margin sediments are more organic and more com-pressible than similar types of sediments from higher-latitude areas. The only sediments showing comparableplasticity characteristics are those blanketing the lowercontinental slope of the eastern United States betweenthe Wilmington Canyon and Cape Hatteras.

It appears likely that the high sedimentation rates de-termined for the Quaternary sediments of the Guate-malan continental margin are due, in part, to the highlyplastic nature of the hemipelagic sediments. These sedi-ments are located on a tectonically active continentalmargin and may be dominated by Theologically con-trolled downslope transport processes, including mud-flows and cohesive debris flows.

ACKNOWLEDGMENTS

I thank William Harrison and Joseph Curiale for providing or-ganic carbon analyses on the samples used for Atterberg limits. I alsothank Bobb Carson, Richard Bennett, and Joseph Kravitz for theirsuggestions, which helped to improve this manuscript.

REFERENCES

Casagrande, A., 1948. Classification and identification of soils. Am.Soc. Eng. Trans., 113:901-931.

Davie, J. R., Fenske, C. W., and Serocki, S. T., 1978. Geotechnicalproperties of deep continental margin soils. Mar. Geotechnol.,3(1):85-119.

Keller, G. H., 1971. Engineering properties of Greenland and Nor-wegian basin sediments. In Proc. First Int. Conf. on Port andOcean Engineering under Arctic Conditions, Vol. II, pp.1285-1311.

Keller, G. H., Lamber, D. N., and Bennett, R. C , 1979. Geotechnicalproperties of continental slope deposits—Cape Hatteras to Hy-drographer Canyon. Soc. Econ. Paleontol. Mineral. Spec. Publ.27, pp. 131-151.

Lambe, T. W., 1951. Soil Testing for Engineers: New York (JohnWiley & Sons), p. 165.

Lowe, D. R., 1979. Sediment gravity flows: their classification andsome problems of application to natural flows and deposits. Soc.Econ. Paleontol. Mineral. Spec. Publ. 27, pp. 75-82.

Richards, A. F., and Fager, E., 1980. Water content and Atterberglimits of sediments at DSDP Holes 417A and 418A, Legs 51 and52, West Atlantic Ocean. In Robinson, P., Flower, M., Salisbury,M., et al., Init. Repts. DSDP, 51, 52, 53, Pt. 2: Washington (U.S.Govt. Printing Office), 1453-1455.

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