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UNITED STATES DEPARTMENT OF THE INTERIOR 

Harold L. Ickes, Secretary

GEOLOGICAL SURVEY 

W/. C. MendenhaD, Director

Professional Paper 186—N

RELATION OF SALINITY

TO THE CALCIUM CARBONATE CONTENT

OF MARINE SEDIMENTS

BY

PARKER D. TRASK

Shorter contributions to general geology, 1936

(Pages 273-299)

UNITED STATES

GOVERNMENT PRINTING OFFICE 

WASHINGTON : 1937

For sale by the Superintendent of Documents, Washington, D. C. ------ Price 20 cents

CONTENTS

Abstract- _______________________________________

Introduction_____________________________________

Factors influencing the calcium carbonate content of. 

sediments——__________________________________

General factors_______________________________

Solubility of calcium carbonate in sea water.______

Main factors_____________________________

Influence of carbon dioxide______-_____----__

Effects of individual factors____________________

Temperature__ ___________________________

Salinity ___________________________________

Organisms.________________________________

Depth________________________________

Calculation of effect of change in temperature and salinity 

on solubility of calcium carbonate__________________

Method of calculation_________________________

Results——____________________________________

Significance _ _________________________________

Statistical study of relations.________________________

Method of study_________________________._____

Control of extraneous factors._______________

Method of comparing salinity and calcium 

carbonate content________________________

Source of data____--___--___-__-______l_-__

Method of compiling data___________________

Page

273

274

274

274

275 

275 

27o

277

277

277

278

278

279

279

279

280

280

280

281

282

283

283

Statistical study of relations—Continued.

Arithmetic means_____________-__---__-_-----_-

Method of presenting data________________

Results —'___---_____--__-____-_ — -___-_---

Graphic presentation___-_________-___---_---_-

Method of plotting. ___________-____--_-_-_-

Relation for salinity._______-______-____--_-

Relation for depth________________________

Relation for surface temperature _______—____

Coefficients of correlation________________ — ____

Significance of statistical data____________________

Areal relations of calcium carbonate content of sediments.

Preparation of map___-____-___--_________-----_

Source of data______________ ——— _________

Classification of data___________ — ________

Reliability of map_________________-_-__-__-

Results__________________________ j.__________-

Areas in which relations are definite._________

Areas in which relations do not seem to hold-....

Comparison with results of other lines of attack. 

Explanation of relationships___________--_____---___-

Geologic application of relationships __________________

Formation of red clay______.______________-----_

Relation of calcium carbonate content of ancient 

sediments to climate-_-----------___----------

Page 

284 

284

286

287

287

287

289

290

290

292

293

293

293

293

293

295

295

295

296

296

297

297

298

ILLUSTRATIONS

PLATE 71. Map of the ocean showing the calcium 

carbonate content of the sediments, the 

salinity of the surface water, and the depth 

of water___________-____-_________---__

FIGURE 12. Relation of calcium carbonate content of 

marine sediments to the salinity of the 

surface water for temperatures of 0° to 

10° C________________________________

13. Relation of calcium carbonate content of 

marine sediments to the salinity of the 

surface water for temperatures of 10° to 

20° C_ _____________________

14. Relation of calcium carbonate content of 

marine sediments to the salinity of the 

surface water for temperatures of 20° to 

25° C_-____---------_-______-_.______

Page

294

288

288

289

FIGURE 15. Relation of calcium carbonate content of 

marine sediments to the salinity of the 

surface water for temperatures of 25° to 

30° C_______________________

16. Relation of calcium carbonate content of 

marine sediments to the salinity of the 

surface water; average for all temperatures.

17. Relation of calcium carbonate content of 

marine sediments to the depth of water___

18. Relation of calcium carbonate content of 

marine sediments to the temperature of the 

surface water________________________

19. Map of the ocean showing the mean annual 

salirity and temperature of the surface 

water_ _______________________________

in

Page

289

290

290

292

294
IV CONTENTS

TABLES

Page

1. Effect of a small rise in salinity and temperature on the

solubility of calcium carbonate in sea water.______ 279

2. Relation of calcium carbonate content of marine 

sediments to salinity of surface water, as indicated 

by individual environments of deposition.________ 281

3. Relation of calcium carbonate content of pelagic 

deposits to depth of water in areas in which the 

surface water has a salinity greater than 36 parts per 

thousand and a temperature higher than 25° C_ _ 284

4. Mean calcium carbonate content of marine sediments 

for different salinity and temperature of the surface 

water and for different depth of water; data arranged 

to show relation for depth.. ______________________ 285

Page

5. Mean calcium carbonate content of marine sediments 

for different salinity and temperature of th'e surface 

water and for different depth of water; data arranged 

to show relation for temperature. ___________ — ____ 286

6. Comparison of*the relation of the calcium carbonate 

content of marine sediments to the salinity of the surface water, the temperature of the surface water, and 

the depth of water, as indicated by arithmetic means. 287

7. Comparison of the relation of the calcium carbonate 

content of marine sediments to the salinity of the surface water, the temperature of the surface water, and 

the depth of water, as indicated by coefficients of 

correlation. ___________________________________ 291
RELATION OF SALINITY TO THE CALCIUM CARBONATE CONTENT OF MARINE

SEDIMENTS

By PAEKEE D. TRASK

ABSTRACT

The calcium carbonate content of sediments is influenced by 

many factors, such as temperature, depth, salinity, hydrogen-ion 

concentration of the water, degree of saturation of the water 

with calcium carbonate, activity of living organisms, and proportion of terrigenous debris in the sediments. Many of the 

factors are interrelated. The temperature, for example, affects 

the solubility of calcium carbonate in sea water, it influences the 

growth of living organisms, it varies the salinity because of its 

effect on evaporation, and it modifies the action of several other 

factors. Most of the factors that affect the formation and 

deposition of calcium carbonate operate simultaneously, and the 

relative importance of the effects of the individual factors varies 

in different parts of the ocean. It is difficult, therefore, to 

isolate a single factor and ascertain the magnitude of its effect 

in comparison with the effect of some other factor. This paper, 

however, is an attempt to discuss the relation of the calcium 

carbonate content of marine sediments to the salinity of the 

water, with particular reference to the surface layers. •

The problem is approached in three ways—(1) by a discussion 

of the effect of the salinity upon the solubility of calcium carbonate in sea water (because of the dominant influence of the 

solubility on the formation of solid calcium carbonate in the 

sea); (2) by a statistical study of the relation of the salinity to 

the calcium carbonate content of sediments in many parts of 

the world; and (3) by the preparation of a map showing the distribution of calcium carbonate on the floor of the ocean with 

respect to the salinity of the surface water. In each of these 

lines of attack the effect of temperature is also considered, so 

that the influence of salinity may be compared with the effect of 

a factor whose influence is generally recognized.

The studies of the solubility relations indicate that in the 

upper layers of water, in which presumably most of the solid 

calcium carbonate is formed, an increase in salinity from 34 to 

35 parts per thousand raises the degree of saturation of the 

water with respect to calcium carbonate 8.4 percent, and that 

an increase in temperature from 20° to 21° C. raises the degree 

of saturation 4.6 percent. That is, a rise of 1 part per thousand 

in salinity affects the solubility of calcium carbonate approximately as much as an increase of 2° in temperature. In many 

parts of the ocean the salinity of the surface water changes 1 

part per thousand in roughly the same distance as the temperature of the surface water changes 2°. The surface temperature, 

however, varies more during the course of a year than the surface 

salinity, and the temperature decreases greatly with depth, but 

the salinity does not. It would seem, therefore, that in several 

parts of the ocean salinity has as great an effect as temperature 

on the solubility of calcium carbonate, but that the total effect 

of salinity on the solubility is less than that of temperature.

In the statistical part of the investigation the relation of the 

calcium carbonate content of the sediments to the surface 

salinity, surface temperature, and depth was ascertained by a 

series of averages, by graphs based on these averages, and by 

coefficients of correlation of the data represented by these averages. The surface salinity and surface temperature were considered because of the importance of the upper layers of water 

in the formation of solid calcium carbonate. However, subsequent to the compilation of the statistical results, it has been 

shown by other workers that the upper 200 meters of water 

probably represents the zone in which most of the solid calcium 

carbonate is formed. Consequently the results might have 

been more reliable if the average salinity and average temperature in this zone had been considered instead of surface salinity 

and temperature. The surface salinity indicates the average 

salinity in this zone better than the surface temperature indicates the average temperature. This difference may account 

for the better relation that was found between calcium carbonate 

and surface salinity than between calcium carbonate and surface 

temperature.

The series of averages and the accompanying graphs indicate 

that the calcium carbonate content of the sediments increases as 

the surface salinity rises. The rate of rise in calcium carbonate 

content is greatest between salinities of 34 and 36 parts per 

thousand. Sediments in areas in which the salinity of the 

surface water is less than 34 parts per thousand in general 

contain less than 5 percent of calcium carbonate, and those in 

areas in which the salinity is more than 36 parts as a rule contain 

more than 50 percent of calcium carbonate. The critical salinity 

seems to be about 35 parts per thousand, which is approximately 

the average for the ocean. The calcium carbonate content of 

the sediments likewise increases as the temperature increases 

and as the depth, decreases.

The relation for the surface temperature is less well defined 

than that for salinity or that for depth. The critical depth 

with respect to calcium carbonate content of the sediments 

seems to be about 1,500 fathoms, as the calcium carbonate 

content of sediments in water less than 1,500 fathoms deep is 

much more nearly constant than that of sediments in water 

more than 1,500 fathoms deep, particularly for sediments that 

were laid down near the shore.

The results of the determination of the coefficients of correlation are similar to those based on the averages. (The coefficient of correlation is a mathematical expression of the degree 

of relationship between two variables, such as calcium carbonate 

content of sediments and surface salinity.) The coefficients of 

correlation indicate that the calcium carbonate content is fairly 

definitely related to surface salinity for both pelagic and nearshore deposits and to depth for pelagic deposits. It is less distinctly related to depth for near-shore deposits and to temperature for both near-shore and pelagic deposits.

The areal distribution of calcium carbonate on many parts of 

the sea floor varies in sympathy with the surface salinity and to 

a smaller extent with surface temperature, but on several parts, 

notably in the South Atlantic, it does not. The results of an 

empirical investigation of this type are naturally attended by a 

certain amount of ambiguity due to the effect of other factors, 

such as the proportion of clastic material, that mask the effect 

of salinity; but they are sufficiently reliable to indicate that the 

surface salinity is definitely related to the calcium carbonate 

content of the sediments and that its effect is similar in order

273
274 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1936

of magnitude to the effect of surface temperature. The empirical relations of the calcium carbonate content of the sediments thereby agree with the solubility relations of calcium 

carbonate in sea water in indicating that salinity is an important 

factor in the deposition of calcium carbonate.

The relation between the calcium carbonate content of sediments and the salinity, however, may in part not be a cause 

and effect relation. It is possible that the surface salinity may 

be a rough index of the degree of saturation of the water with 

calcium carbonate. Thus, areas of high salinity may be supersaturated, with the result that they favor the precipitation of 

calcium carbonate.

Two geologic applications of the results are considered—one 

relating to the deposition of red clay, the other to past climates. 

An increase in degree of saturation of the deep water in the ocean, 

due to an increase in temperature, may result in less calcium 

carbonate being dissolved from particles as they fall to the sea 

floor, thus causing the calcium carbonate content of the sediments to be increased. As red clay is characterized by a small 

calcium carbonate content, the quantity of red clay on the sea 

floor under such conditions would be less than at present. 

Consequently, the scarcity of red clay among ancient sediments may be accounted for by increases in the degree of saturation of the water in the past.

As the calcium carbonate content of sediments in areas of 

high salinity is generally large, and as an arid climate would 

favor the development of high salinity in the sea water, it is 

suggested that some alternations between limestone and calcareous shale or between calcareous shale and noncalcareous 

shale may be indicative of changes in climate. The more calcareous layers would represent more arid periods, when evaporation was high and influx of terrigenous debris was small, and 

the less calcareous layers would represent more humid periods, 

when evaporation was low and influx of terrigenous debris was 

great.

INTRODUCTION

The object of this report is to show that the salinity 

of the sea water is a factor influencing the calcium carbonate content of marine sediments. In order to 

ascertain the relative importance of salinity, the effect 

of salinity on the deposition of calcium carbonate is 

compared with the effect of other factors, chiefly 

temperature. The problem has been approached in 

three ways—- (1) study of the factors influencing the 

deposition of calcium carbonate, with special emphasis 

on the effect of salinity and temperature upon the 

solubility of calcium carbonate in sea water; (2) 

statistical study of the relation of salinity, temperature, 

and depth to the calcium carbonate content of nearshore and pelagic sediments; and (3) preparation of a 

map showing the relation of the areal distribution of 

calcium carbonate on the sea floor to the surface 

salinity, surface temperature, and depth of water. 

The results obtained in all these lines of attack are in 

accord in indicating that salinity is definitely related 

to the calcium carbonate content of sediments.

I am indebted to Dr. Roger Revelle and Dr. E. G. 

Moberg, of the staff of the Scripps Institution of Oceanography, La Jolla, Calif., for assistance in calculating 

the effect of salinity and temperature on the solubility 

of calcium carbonate in sea water, and for their kindness in giving me access to unpublished data. I wish 

to thank Dr. T. Wayland Vaughan, director of the

Scripps Institution, for the privilege of using the 

facilities of the institution while I was procuring some 

of the oceanographic data for this paper. I am also 

under obligation to W. H. Bradley, M. N. Bramlette, 

H. D. Miser, W. W. Rubey, and R. C. Wells, of the 

staff of the United States Geological Survey, both for 

criticising the manuscript and for discussing the problem with me.

FACTORS INFLUENCING THE CALCIUM CARBONATE 

CONTENT OF SEDIMENTS

GENERAL FACTORS

The calcium carbonate content of sediments is 

affected by four main groups of factors—(1) the source 

of particles of calcium carbonate in the water, (2) the 

transportation of the particles while they are being 

deposited, (3) the changes that take place in the 

sediments after the particles have been deposited, and 

(4) the proportion of particles of clastic origin in the 

sediments. The source of calcareous particles in the 

water is the most influential of these four groups of 

factors and is discussed in detail below.

In the transportation of the particles the main considerations are the strength of the currents, the depth 

of water, the size and shape of the particles, the degree 

of saturation of the water with calcium carbonate, the 

rate of solution of calcareous particles, the shape of the 

ocean floor, and the buoyancy of the particles. The 

chief influence of salinity in the transportation of the 

particles is its effect on the degree of saturation of the 

water, which in turn controls the rate of solution of 

'calcareous particles. Salinity influences the density 

of the water, and as the rate at which particles fall 

depends upon their buoyancy—that is, the difference 

•in density between the particles and the liquid through 

which they fall—the salinity might have a very slight 

effect on the rate at which the particles sink. Moreover, in the ocean, currents such as the Gulf Stream 

are caused by the attempt of masses of water of 

different density to come to equilibrium, and as salinity is one of the main factors controlling density, it 

would therefore indirectly affect the transportation of 

particles.

The changes that take place in the sediments after 

the particles ha\e been deposited are mainly connected 

with the processes of diagenesis—that is, lithification. 

The main factor with which salinity might be associated in the processes of diagenesis is the removal of 

calcium carbonate by solution of particles.

The chief factors governing the proportion of particles 

of clastic origin in the sediments are (1) distance from 

shore—near-shore sediments in general contain much 

clastic debris, and pelagic sediments contain relatively 

little; (2) climate—sediments deposited near arid 

regions consist of less clastic material than those near 

humid regions; (3) relief of land—sediments laid down 

near areas of low relief, like Florida, contain less clastic
RELATION OF SALINITY TO CALCIUM CARBONATE CONTENT OF MARINE SEDIMENTS 275

material than those near areas of high relief, like 

California; (4) location with respect to the mouths of 

streams—sediments off the mouths of large streams 

contain much more clastic debris than those off small 

streams; and (5) the rate at which calcareous particles 

are added to the sediments. The salinity of the water, 

except for its effect on the rate at which calcareous 

particles are added to sediments, influences but slightly 

the quantity of clastic debris in the sediments.

Calcium carbonate gets into the water hi a solid form 

in three ways—(1) by chemical precipitation, (2) as 

remains of living organisms, and (3) as detrital particles 

derived from limestone. The presence of limestone 

areas in the drainage basins of streams entering the 

sea may locally be the main source of calcium carbonate 

in sediments deposited near shore; but in general the 

calcium carbonate content of marine sediments is due 

chiefly to chemical precipitation or remains of organisms. The relative importance of these two sources is 

a controversial problem that has not yet been solved 

satisfactorily. In fact, so little is known about the 

processes by which organisms extract calcium carbonate from water for their bodily needs that it seems 

impracticable to attempt to discuss this phase of the 

subject in the present report. However, both chemical 

precipitation of calcium carbonate and the formation 

of calcareous material by organisms are favored by 

increased saturation of the sea water with calcium carbonate.

SOLUBILITY OF CALCIUM CARBONATE IN SEA WATER

MAIN FACTORS

The solubility of calcium carbonate hi sea water 

has been studied intensively in the past few years by 

several workers, among whom are Moberg, Revelle, 

and their associates at Scripps Institution; Buch, 

Gripenberg, and their associates at Helsingfors; and 

Wattenberg, who accompanied the Meteor expedition 

to the South Atlantic. 1 The discussion of the solubility 

relations of calcium carbonate in the present report is 

based on the work of these investigators. As their 

publications describe the problem in full and contain 

extensive bibliographies, only a summary of the features 

that relate to the question of salinity is included here.

The chemical precipitation of calcium carbonate 

depends upon the degree of saturation of the water with 

calcium carbonate. If the water is undersaturated, 

solid particles of calcium carbonate can pass into solution ; if it is oversaturated, solid particles can be formed 

by precipitation from the water. Precipitation, howi Moberg, E. G., Greenberg, D. M., Revelle, R., and Alien, E. C., The buffer 

mechanism of sea water: Scripps Inst. Oceanography Bull., Tech. ser., vol. 3, no. 11, 

pp. 231-278, 1934. Buch, K., Harvey, H. W., Wattenberg, H., and Gripenberg, 8., 

Ueber das KohlensSuresystem im Meerwasser: Conseil perm. expl. mer Rapports 

et proces-verbaux, vol. 79, pp. 1-70,1932. Wattenberg, H., Kalziumkarbonat- und 

Kohlensauregehalt des Meerwassers: Wiss. Ergeb. Deutschen Atlantische'n Exped. 

Meteor, 1925-27, Band 8, Toil 2, pp. 1-333, 1933. Revelle, R., and Fleming, R. H., 

The solubility product constant of calcium carbonate in sea water: 5th Pacific Sci. 

Gong., Victoria and Vancouver, Proc., vol. 3, pp. 2089-2092, 1933. Revelle, R. 

Physicochemical factors affecting the solubility of calcium carbonate in sea water: 

Jour. Sedimentary Petrology, vol. 4, pp. 103-110, 1934.

ever, does not necessarily take place as soon as the 

saturation point is reached. The water can become 

supersaturated to a considerable extent before beginning to produce solid calcium carbonate. The precipitation of calcium carbonate from solution is favored 

by the presence in the water of solid particles, either 

of calcium carbonate or of something else. The instigation of precipitation by such an action is called 

"seeding."

The saturation point depends upon the law of mass 

action. That is, the water is saturated when the 

product of the concentration of calcium and carbonate 

equals a constant, called the "apparent solubility 

product constant." The relation expressed symbolically is

The apparent solubility product constant is practically 

independent of the quan'tity of calcium carbonate or 

the concentration of calcium and carbonate in the 

water, but it is not constant with respect to other 

variables, for if the temperature, salinity, pressure, or 

concentration or kinds of ions other than calcium or 

carbonate change, the apparent solubility product 

constant likewise changes.

If the concentration of calcium is high, a small concentration of carbonate will make the water saturated 

with respect to calcium carbonate, and if the concentration of calcium is low, a large concentration of carbonate is needed to make the water saturated. If the 

product of calcium and carbonate exceeds the apparent 

solubility product constant, calcium carbonate can be 

removed from solution by precipitation of solid calcium 

carbonate until the product of the calcium and carbonate ions equals the solubility product constant, but 

whether or nqt under any particular circumstances 

calcium carbonate will be precipitated in the sea 

depends on the laws governing supersaturation, which 

are not yet well understood.

According to the relations governing the solubility of 

calcium carbonate in the sea, three main factors, therefore, are concerned — (1) the concentration of calcium, 

(2) the concentration of carbonate, and (3) the apparent 

solubility product constant. The concentration of 

calcium at any given depth 2 depends almost entirely 

upon the salinity, because the salinity represents the 

concentration of total sdlids in solution, and if the 

salinity changes, then it follows that the concentration of all the salts, including those of calcium, likewise 

changes. The apparent solubility product constant is 

influenced by several factors, including temperature and 

salinity. It increases with rise in salinity and decreases 

with rise in temperature (table 1). The concentration 

of carbonate depends upon a large number of variables 

and is by far the most influential factor in the deposition 

of calcium carbonate.

* Revelle, R., Physicochemical factors affecting the solubility of calcium carbonate in sea water: Jour. Sedimentary Petrology, vol 4, p. 107,1934.
276 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1936

INFLUENCE OP CARBON DIOXIDE

Carbonate ions represent one of the three forms in 

which carbon dioxide occurs in sea water. The other 

two forms are bicarbonate ions and carbonic acid. 

For a strictly accurate discussion, carbonic acid and 

free carbon dioxide should be considered separately, but 

then* effects are so nearly alike that for the purpose 

of this discussion they are treated as one variable.3

These three forms of carbon dioxide are related to one 

another according to definite laws, which are expressed 

symbolically as follows:

[H2C03] --"*" 

fcH+KCQ,-]^,

[Hcori 2 "

£=[HCOr]4-2[C03 - ]

.(1)

.(2) 

(3)

In these equations B is the equivalent concentration of 

titratable base; aH, the activity or effective concentration of hydrogen ions as indicated by the pH; K^ and 

KZ, the respective apparent dissociation constants 

of the first and second steps in the ionization of carbonic 

acid; and the brackets denote molar concentration.4

The first equation indicates that the concentration 

of bicarbonate depends upon the concentration of 

hydrogen ions a,nd undissociated carbonic acid and on a 

constant KI', called the "first apparent dissociation 

constant of carbonic acid." The second equation indicates that the concentration of carbonate depends 

upon the concentration of hydrogen and bicarbonate 

and upon a constant K2 f, called the "second apparent 

dissociation constant of carbonic acid." Thus if the 

concentration of any one of the three forms of carbon 

dioxide—namely, carbonate, bicarbonate, or carbonic 

acid—should change, the concentration of the other 

two forms must also change in order to satisfy the relations expressed in equations 1 and 2. The two apparent dissociation constants, KI and K2 ', similar to the 

apparent solubility product constant of calcium carbonate, K'Ca,cov are affected by external conditions, 

such as temperature, salinity, and the activity of the 

ions in the solution; but they are practically unaffected 

by the concentration of hydrogen, carbonate, and bicarbonate ions and by carbonic acid.

Sea water, being alkaline, .contains an excess of base 

that can be balanced against a weak acid like carbonic 

acid. At a salinity of 34 parts per thousand the amount 

of carbon dioxide that can be balanced against this excess base is approximately 103 milligrams per liter.5 

As the carbonate radical has double the valence of the 

bicarbonate radical, only one-half as much carbon di-

' Moberg, E. Q., Oreenberg, D. M., Revelle, R., and Alien, E. C., The buffer 

mechanism of sea water: Scripps Inst. Oceanography Bull., Tech. ser., vol. 3, p. 238, 

1934.

* For detailed explanation of these equations see Moberg, E. Q., and others, op. cit., 

pp. 235-268.

s Moberg, E. Q., and others, op. cit., p. 269.

oxide — that is, 51.5 milligrams per liter — in the form of 

carbonate is needed to balance the excess base. If the 

quantity of carbon dioxide were intermediate between 

51.5 and 103 milligrams per liter, part of the base could 

be balanced by carbonate and part by bicarbonate. 

The relation is expressed symbolically in equation 3. 

This equation, however, is not strictly accurate, because part of the excess base is balanced by acids of 

boron 6 and perhaps by other acids as well. According 

to Kevelle and Fleming, the influence of borate becomes 

greater as the hydrogen-ion concentration decreases — 

that is, as the pH increases. At a hydrogen-ion concentration of 10~9 — that is, at a pH of 9 — about 16 percent of the excess base is balanced by borates, but at a 

pH of 8.0 to 8.2, which is the general average for the 

surface of the sea, the proportion of excess base balanced 

by borates is less than 4 percent,7 which indicates that 

nearly all the excess base is balanced by some form of 

carbonic acid. Below the surface of the ocean the pH 

decreases to about 7.8,8 and the influence of boron is insignificant. Equation 3, which shows the relation of 

carbonic acid to excess base, therefore seems to be 

approximately correct for the conditions that usually 

prevail in the sea, but to be strictly accurate it should 

include the effect of boron.

Similarly, to be strictly accurate the excess base 

should be corrected for the effect of hydrogen and 

hydroxyl ions, but according to Moberg and his associates 9 this effect is not great for conditions that ordinarily prevail in the sea. Consequently, in order to 

simplify the calculations, the effect of these ions on the 

excess base was not considered in connection with 

equation 3.

The distribution of the three forms of carbon dioxide 

in the water therefore depends on the three fundamental relations expressed by equations 1, 2, and 3. 

These three equations may be solved simultaneous!^ 

and the total effect expressed as follows:

An expression for the concentration of carbonate instead of the bicarbonate could have been given, but it 

would be in a form that would make numerical computation difficult .

It follows from equations 1 to 4 and also from experimental work of Moberg and his associates 10 that the 

hydrogen-ion concentration increases — or, as generally

6 Revelle, R., and Fleming, R. F., The solubility product constant of calcium 

carbonate in sea water: 5th Pacific Sci. Oong., Victoria and Vancouver, Proc., vol. 3, 

pp. 2089-2092, 1933.

7 Buch, K., Der Bors&uregehalt des Meerwassers und seine Bedeutung bei der 

Berechnung des Kohlensauresystems im Meerwasser: Conseil perm. expl. mer 

Rapports et proces-verbaux, vol. 85, pp. 71-75, 1933.

8 Wattenberg, H., Kalziumkarbonat- und Kohlens&uregehalt des Meerwassers: 

Wiss. Ergeb. Deutschen Atlantischen Exped. Meteor, 1925-27, Band 8, Teil 2, pp. 

268-308, 1933.

• Moberg, E. Q., and others, op. cit., pp. 243-244.

i« Idem, p. 269.
RELATION OF SALINITY TO CALCIUM CARBONATE CONTENT OF MARINE SEDIMENTS 277

reported, the pH decreases—as the total content of 

carbon dioxide rises. Thus, at a pH of 8.5 the total 

content of carbon dioxide is about 83 milligrams per 

liter, of which about 20 milligrams is in the form of 

carbonate, 63 milligrams in the form of bicarbonate, 

and less than 1 miUigram in the form of carbonic acid. 

At a pH of 8.1, which prevails at the surface of the 

ocean, the total content of carbon dioxide is about 93 

milligrams, of which 10 milligrams occurs as carbonate, 

83 milligrams as bicarbonate, and less than 1 milligram 

as carbonic acid; and at a pH of 7.5, the total content 

of carbon dioxide is about 104 milligrams, of which less 

than 1 milligram is carbonate, 103 milligrams bicarbonate, and about 1 milligram carbonic acid. As the 

pH falls below 7.5 the total content of carbon dioxide 

rises. This increase is almost entirely in the free carbon dioxide or carbonic acid. The content of carbon 

dioxide in the form of bicarbonate and carbonate 

remains about 103 milligrams and less than 1 milligram per liter, respectively.

• The relationships expressed above indicate that between pH 7.5 and 8.5, which represents practically the 

entire range for the sea, each unit decrease in total 

quantity of carbon dioxide means a decrease of two 

units in bicarbonate and an increase of one unit in 

carbonate. That is, each decrease of 1 milligram in 

total content of carbon dioxide causes an increase of

I milligram of carbon dioxide in the form of carbonate. 

The gain in carbonate, however, is slightly less than 

the loss in total content of carbon dioxide, because a 

decrease in total content of carbon dioxide causes an 

increase in the pH of the water, which in turn causes 

more of the excess base to be balanced by borates. 

Consequently, part of the base that would have to be 

balanced by carbonate if borates were not* present is 

balanced by borates, and not so much carbon dioxide 

changes from bicarbonate to carbonate.

This relation of carbonate to total content of carbon 

dioxide is probably the most significant factor in the 

deposition of calcium carbonate, as it is most susceptible to change. The total content of carbon dioxide 

ranges chiefly between 90 and 95 milligrams per liter 

in the upper layers of the sea, where, as discussed below, 

most of the calcium carbonate seems to be formed. 11 

The carbon dioxide in the form of carbonate under such 

conditions ranges between 8 and 12 milligrams per liter. 

Thus, a decrease of only 1 percent in the to tall con tent 

of carbon dioxide causes an increase of about 10 percent in the quantity of carbonate. It follows, therefore, 

that small changes in the total quantity of carbon dioxide in the water have a very pronounced influence on 

the solubility of calcium carbonate.

The relations governing the quantity of carbonate 

in the sea water, however, as indicated &y the foregoing

II Moberg, E. G., and others, op. cit., p. 269.

discussion, are complicated. The controlling factors 

are the concentration of carbonic acid and bicarbonate, 

the total content of carbon dioxide, the hydrogen-ion 

concentration, and the two apparent dissociation constants of carbonic acid, KI and K2 f . These factors, 

in addition to being interrelated to some extent, are 

also influenced by other factors. The content of carbonic acid depends upon the content of free carbon 

dioxide, which in turn is directly affected by the solubility of carbon dioxide in sea water, by the carbon 

dioxide tension in the air above the water, and by the 

activity of the organisms in the water. The solubility of free carbon dioxide in the water and the two 

apparent dissociation -constants, K^ and K2 f , are influenced considerably by the temperature and salinity. 

The quantity of excess base in the water depends 

directly upon the salinity, but it is not affected significantly by small changes in temperature (table 1).

EFFECTS OF INDIVIDUAL FACTORS

The foregoing analysis shows that the deposition of 

calcium carbonate in the sea is affected by many factors and that several of these factors influence the 

deposition of calcium carbonate in different ways.

TEMPERATURE'

The temperature of sea water affects the solubility 

of calcium carbonate in the water because of its influence on (1) the solubility of free carbon dioxide in the 

water, (2) the apparent solubility product constant, 

K'c&cov (3) the two apparent dissociation constants of 

carbonic acid, KI and K2 f, and (4) the hydrogen-ion 

concentration. It also influences the growth of living 

organisms, which in turn affect the deposition of calcium 

carbonate in several ways. Moreover, owing to its 

effect on evaporation, it influences the salinity of the 

water. As the temperature changes with depth, it also 

influences the relations for depth. Finally, it has some 

minor effects because of its influence on the viscosity 

and density of the water and because of its relation to 

the formation of detrital particles by the weathering of 

limestone. __

SAIjTNJLTY

The salinity of sea water influences the solubility of 

calcium carbonate in the water because of its relations 

to (1) the solubility of free carbon dioxide in the water, 

(2) the constants, K^, K2 ', and Krc&COv (3) the hydrogen-ion concentration, and (4) the quantity of calcium 

and excess base in the water. Lake the temperature, 

it affects the viscosity and density of the water and 

the growth of living organisms. Owing to its effect 

on the density of water, it influences the circulation 

of masses of water in the ocean, with the result that 

bodies of warm or cold water are moved from their 

places of formation; and thus the salinity indirectly 

affects the temperature of the water.

92918—37-
278 SHOETER CONTRIBUTIONS TO GENERAL GEOLOGY, 1936

ORGANISMS

Living organisms may remove calcium carbonate 

directly from the water to make shells and skeletal 

material. They may transport particles of calcium 

carbonate in their digestive tracts. Forms like bacteria may precipitate calcium carbonate directly,12 or, 

as suggested by Revelle,13 they may instigate the precipitation of calcium carbonate from supersaturated 

water by a seeding action induced by the presence of 

their bodies in the water. Living organisms may give 

off waste products, such as ammonia, which may affect 

the solubility of calcium carbonate. 14 The most important action of living things in the sea with respect 

to the precipitation of calcium carbonate, however, is 

their effect on the part played by carbon dioxide in the 

water.

The floating plants (phytoplankton) living in the 

surface layers of the water remove large quantities of 

carbon dioxide from the water for building organic 

compounds in their tissues by the aid of photosynthesis. The animals living in the sea, on the other 

hand, give off carbon dioxide as a waste product. The 

decomposition of the tissues of dead plants and animals 

as they fall to the bottom of the sea results in the 

addition of carbon dioxide to the water. The phytoplankton is confined chiefly to the upper 200 meters of 

water, in which light penetrates effectively for photosynthesis. 15 The animals are found at nearly all 

depths but are largely confined to the upper layers, in 

the zone of phytoplankton, which forms their basic 

source of food. Decomposition takes place at all 

depths, but its effect is more evident in the water 

beneath the zone of phytoplankton. In the upper 100 

to 200 meters of water the removal of carbon dioxide 

by the phytoplankton is greater than the addition of 

carbon dioxide to the water by animals and by decomposition; 16 but below 200 meters the reverse is 

true. These phenomena cause the upper £00 meters 

of water to contain comparatively little carbon dioxide 

and the water below a depth of 200 meters to contain 

comparatively much carbon dioxide. Consequently, 

the surface layers are relatively rich and the lower 

layers relatively poor in carbonate. The upper layers, 

therefore, are more highly saturated with calcium 

carbonate than the lower layers.

Wattenberg " has prepared maps showing the degree 

of saturation of the water in the South Atlantic, which 

presumably apply in general to the other oceans as

> 2 Bavendamm, W., Die Mikrobiologische Kalkfailung in der tropisehe See: 

Archiv Mikrobiologie, Band 3, pp. 205-276, 1932. This paper contains a good 

bibliography.

i* Revelle, R., personal communication.

» Murray, J., On tBe deposits of the Black Sea: Scottish Geog. Mag., vol. 16, 

p. 684, 1900.

15 Cf. Hentschel, E., Allgemeine Biologie des siid-Atlantischen Ozeans: Wiss. 

Ergeb. Deutschen Atlantischen Exped. Meteor, 1925-27, Band 11, 1933.

" Wattenberg, H., op. cit., pp. 162, 236.

»Idem, pp. 194-205.

well. The surface water ranges from about 100 percent saturation in polar latitudes to about 150 percent 

saturation in equatorial latitudes. Below a depth of 

about 200 meters in polar latitudes and 500 meters in 

tropical latitudes the water everywhere is undersaturated with calcium carbonate, but in no place is 

the degree of saturation reported to be less than 90 

percent.

Wattenberg's maps are based on a determination of 

the apparent solubility product constant that is about 

one-half as large as the determination by Revelle and 

Fleming, 18 made by a different method.

The solubility product constant of calcium carbonate 

in sea water has to be determined experimentally and 

is very difficult to measure. It represents the point of 

equilibrium at which no calcium carbonate will be dissolved and none will be precipitated from the water. 

The solubility of calcium carbonate in sea water is very 

small, and the water tends to become supersaturated 

before precipitation begins. Consequently, it is not 

surprising that the results of Wattenberg should differ • 

by 50 percent from those of Revelle and Fleming. The 

gratifying feature is that they are as close to one another 

as they are. It would seem, therefore, that the proper 

order of magnitude of the apparent solubility product 

constant has been ascertained. However, because 

Revelle and Fleming's determination of this constant 

is distinctly greater than Wattenberg's, the estimates 

of the degree of saturation for the South Atlantic given 

by Wattenberg may be too high. It nevertheless seems 

probable that the upper layers of water in the ocean, 

especially in low latitudes, are saturated with calcium 

carbonate and that the water below 200 meters is 

undersaturated.

. DEPTH

The depth of water, therefore, is an important factor 

in the deposition of calcium carbonate. The upper 

layers of water, which appear to be saturated with calcium carbonate, represent the zone in which calcium 

carbonate is formed by chemical precipitation, and they 

also represent the zone in which most of the skeletal 

material, composed of calcium carbonate, is produced 

by the action of living organisms. The layers below a 

depth of 200 meters, where the water is undersaturated 

with calcium carbonate, represent a zone where calcium 

carbonate may be dissolved from particles as they sink 

to the sea floor.

Depth, because of its relation to pressure, also affects 

the solubility of calcium carbonate. 19 In addition, the 

temperature of the water decreases from the surface 

downward, with the result that the deep water can hold 

more calcium carbonate in solution than the surface 

layers. The saljnity of the deep ocean water is remark- 

's Revelle, R., and Fleming, R. F., op. cit., p. 2091. 

w Wattenberg, H., op. cit., p. 209.
RELATION OF SALINITY TO CALCIUM CARBONATE CONTENT OF MARINE SEDIMENTS 279

ably constant and differs but little from the general 

average of the ocean.20 The influence of salinity on 

calcium carbonate because of changes in depth, therefore, is not great.

CALCULATION OF EFFECT OF CHANGE IN TEMPERATURE AND SALINITY ON SOLUBILITY OF CALCIUM 

CARBONATE

METHOD OF CAICUIATION

The effect of changes in salinity and temperature on 

the solubility of calcium carbonate in sea water can be 

computed from the relations given in equations 1 to 4 

and from the .apparent solubility product constant. 

The quantity of carbonate in the water can be calculated 

from equations 3 and 4. The content of bicarbonate is 

determined from equation 4 by substitution of the 

figures for carbonic acid, excess base, and the two apparent dissociation constants, KI and K2 '. The carbonate 

content is then readily obtained by substitution of the 

figures for bicarbonate and excess base in equation 3.

In order to show the effect of increase in temperature 

and salinity, the solubility of calcium carbonate in sea 

water was calculated for three sets of conditions—(1) a 

standard condition in which the temperature was 20° 

C. and the salinity was 34 parts per thousand; (2) where

the temperature was 1° higher but the salinity was the 

same; and (3) where the salinity was 1 part per thousand higher but the temperature was the same (table 1). 

For the standard condition the carbonate content of a 

saturated solution was computed on the basis of a 

hydrogen ion concentration of 10~8, or a pH of 8.0 

(which is determined mainly by the amount of carbonic 

acid in the water), a first apparent dissociation constant 

of 1.07 X 10~6 (pKi'=5.97), a second apparent dissociation constant of 8.9 X 10~i0 (pK2 '~9.Q5), and an excess 

base equivalent to 103 milligrams of carbon dioxide 

in the form of bicarbonate. The carbonate content for 

the conditions of increased temperature and salinity 

was likewise computed by substitution of the proper 

figures for carbonic acid, KI , K2 ', and excess base in 

equations 3 and 4. The changes in KI , K2 , and carbonic acid (in reality, in the solubility of free carbon 

dioxide in saline solutions) corresponding to the changes 

in temperature and salinity were based on data presented by Buch and his associates. 21 The excess base 

was assumed to vary directly with the salinity and to be 

unaffected by temperature. The effect of boron was 

disregarded, but, as mentioned above, at a hydrogen 

ion concentration of 10~8 , the effect of boron is slight.

TABLE 1.—Effect of a small rise in salinity and temperature on the solubility of calcium carbonate in sea water

Free CO2 (assumed to be equivalent to [HjCOs]) ___. __

Second apparent dissociation constant of carbonic acid

Excess base (titrat ion alkalinity) , B _ _ _ ___ ____

Concentration of bicarbonate [HCO3~]______ __ ____

Concentration of carbonate [CO 3 — ]_____ _____

Concentration of calcium [Ca++]._ __ __ ___

Apparent solubility product constant of calcium carbon 

Degree of saturation of sea water with calcium carbona

°c

3+] [HCOs~] „ t

[H2C03 ] Kl -------------

[«H+] [CO3~] „ ,

[HCO,-] ^ -----------

, [Ca++] [CO,— J

*V CaCO3

Standard

20 

34

1.000 

1.000

1.000

1.000

1.000 

1.000 

1.000 

1.000 

1.000

1.000

Eise in temperature

21 

34

0. 974 

1.015

1.023

1.007

1. 000 

. 995 

1.025 

1.000 

.978

1.046

Rise in salinity

20 

35

0.996 

1. 008

1.047

1. 016

1.029 

• 1. 020 

1.085 

1.029 

1.030

1.084

RESUITS

The results o| the calculations are presented in 

table 1. The computations are given in the ratio form 

so that percentage changes in the size of the different 

variables will be readily apparent. For a rise in temperature of 1° C. the carbonate content increases 2.5 

percent, and for a rise in salinity of 1 part per thousand 

the carbonate content increases 8.5 percent.

20 Defant, A., Die vertikale Verteilung von Temperatur und Salzgehalt im Weltmeere: Qesell. Erdkunde Berlin Zeitschr., Jahrg.,1930, pp. 28-42. Wiist, G., Schichtung und Tiefenzirkulation des Pazifischen Ozeans: Inst. Meereskunde Veroffentl., 

A, Heft 20, 1929. Sverdrup, H. W., The deep water of the Pacific, according to the 

observations of the Carnegie: Internat. Qeod. and Qeophys. Union, Eepts. Stockholm 

meeting, pp. 87-93, Carnegie Inst. Washington, Dept. Terrestr. Magnetism, 1930.

The content of calcium ions was assumed to vary 

proportionately with the salinity and to be unaffected 

by the rise in temperature. As the salinity increased 

2.9 percent, the calcium content likewise increased 2.9 

percent. The changes in the apparent solubility 

product constant were computed from data given by 

Wattenberg. 22 For the increased temperature the 

apparent solubility product constant was lowered 

2.2 percent, and for the increased salinity it was raised 

3.0 percent.

As the sea water is completely saturated with calcium 

carbonate when the product of the calcium and car21 Buch, K., and others, op. cit. (1932), pp. 46, 54, 63.

22 Wattenberg, H., op. cit., pp. 199, 203.
280 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1936

bonate equals the apparent solubility product constant, 

the degree of saturation of the water with calcium

carbonate can be expressed by a ratio *• a ^, ——-—-•

-tV CaCO3

If the ratio is greater than 1.0 the water is oversaturated; if less than 1.0 it is undersaturated; and if equal 

to 1.0 it is exactly saturated.

The degree of saturation of the water for the three 

chosen sets of conditions can therefore be calculated 

by the substitution of the proper figures for [Ca++], 

[CO3—], and K'c&coz in this ratio. In the standard 

condition the ratio is unity and the water is exactly 

saturated. Where the temperature is 1° higher the 

water is 4.6 percent oversaturated, and where the 

salinity is 1 part per thousand higher the water is 8.4 

percent oversaturated. That is, according to this 

table, at a temperature of 20°, a salinity of 34 parts 

per thousand, and a pH of 8.0, a rise of 1° in temperature increases the degree of saturation 4.6 percent, and 

a rise of 1 part per thousand in salinity increases the 

degree of saturation 8.4 percent.

These determinations of the effect of temperature 

and salinity on the solubility of calcium carbonate 

should be classed as estimates. They are believed to 

indicate the proper order of magnitude, but some of the 

variables on which they depend, especially the apparent 

solubility product constant of calcium carbonate, have 

not yet been worked out completely. Consequently the 

determinations may be modified in the future. Wattenberg,23 using a different method of calculation, 

reports a rise in degree of saturation of the water of 

about 3.5 percent, instead of 4.6 percent, for an in- 

• crease of 1° C. in temperature; and Revelle,24 by a. still 

different method in which a correction was made for 

boron, finds a rise of 5.2 percent for an increase of 1° C.

Wattenberg does not calculate the effect of salinity 

on the degree of saturation, but Revelle 2S reports a rise 

of 5.0. percent, instead of 8.4 percent, for an increase 

in salinity of 1 part per thousand. Revelle, though 

having assisted me in calculating the effect of salinity 

on the solubility, when he came to make his own determination took more factors into consideration and 

in part used different data. According to current 

concepts of the solubility of calcium carbonate, his 

estimate is therefore presumably more accurate than 

mine; but the greater effect of salinity indicated by my 

calculations is more nearly in agreement with the 

relation of the calcium carbonate content of sediments 

to the surface salinity indicated by the statistical 

studies described below. The two determinations, 

however, are of the same general order of magnitude and 

demonstrate that the degree of saturation of the water 

with calcium carbonate increases as the salinity rises.

» Wattenberg, H., op. cit., p. 207.

84 Revelle, R., Physicochemical factors affecting the solubility of calcium carbonate 

in sea water: Jour. Sedimentary Petrology, vol. 4, pp. 103-110,1934. 

»5 Idem, p. 207.

SIGNIFICANCE

i

It is evident from the data given in table 1 that the 

salinity definitely affects the solubility of calcium 

carbonate in the sea and therefore influences the 

deposition of calcium carbonate. The magnitude of 

the change in degree of saturation for an increase in 

salinity of 1 part per thousand, compared with the 

magnitude of the change for a rise of 1° in temperature, 

demonstrates that salinity ranks with temperature as a 

factor controlling the solubility of calcium carbonate.

However, it is difficult to ascertain whether or not 

the effect of salinity on the solubility of calcium carbonate in sea water is as great as that of temperature. 

In the upper 200 meters of water, in which most of the 

solid calcium carbonate seems to be formed, the rate 

of change in solubility of calcium carbonate with 

respect to lateral changes in salinity and temperature 

is of the same order of magnitude. This feature is 

illustrated by figure 19, which shows the lines of equal 

temperature and salinity on the surface of the ocean. 

The maximum rate of change in salinity on the surface 

of the open ocean is about 0.4 part per thousand in 

100 miles; in temperature, about 0.7° in 100 miles. 

The effect of this change in salinity on the solubility is 

0.4X8.4=3.3 percent, and the effect of this change in 

temperature is 0.7X4.6=3.2 percent—that is, the 

effects are about the same. The i elation of the areal 

distribution of calcium carbonate in sediments to surface temperature and to salinity, illustrated by plate 71, 

also supports this inference. It would seem, therefore, 

that in some parts of the ocean salinity would influence 

the solubility as much as the temperature. However, 

the seasonal variations of temperature on the surface 

of the ocean during the course of a year are relatively 

greater than those of salinity. Moreover, the temperature decreases greatly with depth, but the salinity 

does not. Consequently the total effect of salinity on 

the solubility of calcium carbonate in the pcean presumably is less than the effect of temperature.

STATISTICAL STUDY OF RELATIONS

METHOD OF STUDY

The relation of the salinity to the calcium carbonate 

content of marine sediments may also be studied statistically. In a previous investigation 26 I compiled a 

table which suggested strongly that the calcium carbonate content of marine sediments is definitely 

related to the 'salinity of the surface water. In this 

table the average calcium carbonate content of the 

sediments in 100 environments of deposition from 

many parts of the world was plotted against the 

salinity of the surface water. Table 2 is a modification 

of this previous table.

* Trask, P. D., Hammar, H. E., and Wu, C. C., Origin and environment of source 

sediments of petroleum, p. 103, Houston, Tex., Qulf Publishing Co., 1932.
RELATION OF SALINITY TO CALCIUM CARBONATE CONTENT. OF MARINE SEDIMENTS 281

TABLE 2. — Relation of calcium carbonate content of marine sediments to salinity of surface water, as indicated by individual 

environments of deposition

Average (median) CaCOs content of 

region (percent)

Oto 2__ __ ... __ .._.._._

3 to 10_ _______ . __ _____

11 to 20 __ ____________ _ _

21 to 50 __ _-_-.--____.___

51 to 88— __-____- ___ --.-

Average (median) 

CaCOs content for 

given salinity 

percent- _

Salinity (parts per thousand)

<34 34-35 35-36 36+

Number of regions

40 

8 

9

1

4 

6 

4 

1

5

3 

6

6

45

2

6 

5

45

According to this table, the sediments in areas in 

which the surface salinity is less than 35 parts per 

thousand contain little calcium carbonate, and those 

in areas in which the salinity is more than 35 parts contain much calcium carbonate. This relationship, 

however, might be more apparent than real, because the 

effects of other factors, such as temperature and depth 

of water, the degree of saturation of the water with 

calcium carbonate, the action of organisms, or the proportion of clastic detritus in the sediments, were not 

considered. The salinity might happen to vary in the 

same way as some of these other factors and thus not 

be definitely related to the calcium carbonate content 

of the sediments.

If the effect of the other factors could be considered 

and if the salinity were then still found to vary with 

the calcium carbonate content, it would be evident that 

the relation is definite. The ideal way to undertake 

such an investigation would be to make all the factors 

except salinity constant, and then examine the relationship between salinity and calcium carbonate. 

Unfortunately, it is impossible to make all the other 

factors constant, but the effect of some of them can 

be determined to a certain extent by means of a 

statistical study of a large number of samples.

CONTROL OF EXTRANEOUS FACTORS

The sea floor can be divided into several areal groups 

representing different conditions of temperature, depth 

of water, and distance from shore; and the relation of 

the salinity to the calcium carbonate content of the sediments in each group can then be examined. The 

size of the groups into which it is practicable to divide 

the sea floor depends upon the number of samples 

available. If the number of samples is large, the size 

of the groups can be small; but if the number of samples is small, the size of the groups must be large, 

because each group should be represented by enough 

samples to counterbalance the effects of factors not 

considered in the selection of the groups. About 2,000

samples were available for study, and the most practicable number of groups into which the sea floor could 

be divided seemed to be 32. The average number of 

samples in each group, therefore, was about 60, which 

should be sufficient to counterbalance to a considerable 

extent the effect of the factors that were not evaluated, 

such as the degree of saturation of the water with calcium carbonate. .

If there are 32 groups, the most practicable grouping 

seems to be to divide the sea into 4 temperature groups; 

divide each of these temperature groups into 4 depth 

groups, making 16 groups; and then divide each of 

these depth groups into 2 groups according to distan.ce 

from shore, making 32 groups in all.

The mean annual temperature of the surface of the 

sea ranges chiefly between 0° and 30° C., but over a 

large area it ranges mainly between 20° and 30°. 

Consequently, instead of making four equal groups based 

on surface temperature, it seemed better to make the 

areal distribution of the groups more nearly equal and 

have the limits of the groups 0°-10°, 10°-20°, 20°-25°, 

and 25°-30°. The limits of the four depth groups were 

0 to 1,000, 1,000 to 2,000, 2,000" to 3,000, and 3,000 to 

4,000 fathoms. In reference to distance from shore, 

the samples were divided into near-shore and pelagic 

groups. All the samples in the near-shore group were 

obtained less than 500 miles from shore and most of 

them within 200 miles of shore. For the most part 

they represent "terrigenous deposits" in the Murray 

classification.27 The pelagic samples represent sediments far from land and are characterized by material 

of chemical and organic origin, in contrast with the 

near-shore deposits, which contain considerable material of clastic origin in addition to that of chemical and 

organic origin. The effect of detrital particles on the 

proportion of calcium carbonate in the sediments is 

compensated to some extent by means of this division 

of the sediments into near-shore and pelagic deposits, 

but it would be better if it had been practicable to 

make more than two ^visions of the sediments with 

respect to distance from shore, because of the possibility that variations in the proportion of detrital 

particles within either the near-shore or the pelagic 

group might obscure the effect of other variables, 

such as temperature or salinity.

In fact, in the entire grouping of the samples the 

limits of the individual groups are so wide that variations within any one of them may mask the relation 

of salinity to calcium carbonate. ^ Ordinarily, variations in calcium carbonate arising from variations 

within a group will tend to counterbalance one another, 

but if the effect of some particular factor, such as 

temperature, or proportion of clastic material, or degree 

of saturation of the water with calcium carbonate,

» Murray, I., and Eenard, A. F., Challenger Kept., Deep-sea deposits, pp. 228-240, 

1891.
282 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1936

should vary in some of the individual groups in the 

same way as the salinity, the relation of salinity to 

calcium carbonate might be completely obscured. 

For example, in certain parts of the sea, notably in 

latitudes greater than 40°, the surface temperature and 

salinity vary in the same way with respect to latitude 

(fig. 19). If within the areal confines of a temperature 

group the salinity should be found to vary with respect 

to horizontal distance in the same way as temperature, 

and if a relation between salinity and calcium carbonate 

of the sediments were found, it would not follow necessarily that the variations in calcium carbonate were 

due to variations in salinity. They might be due in 

part or wholly to variations in temperature within the 

group. A similar degree of indefiniteness would arise 

in areas where the salinity increases away from shore, 

because it would not be certain whether the increase 

in calcium carbonate in the sediments were due to the 

increased salinity or to the smaller proportion of clastic 

material in the sediments.

The possibility of sympathetic variations of this type 

is an inevitable result of a system of grouping in which 

the range within the individual groups is considerable. 

The conclusions obtained from a study of such groups, 

however, though not completely satisfactory, are 

certainly more definite than if no grouping had been 

made. Moreover, it is evident from plate 71 and 

figure 19 that surface salinity in most parts of the 

ocean does not vary in the same way in a horizontal 

direction as surface temperature, depth of water, or 

distance from shore. Furthermore, each of the 32 

individual groups represents several different parts of 

the sea in which the conditions are not everywhere the 

same. The number of samples in the individual 

groups is fairly large, and the samples are distributed 

over many parts of the sea. Therefore, according to 

the laws of probability, the chances are against the 

possibility that the relation of surface salinity to the 

calcium carbonate content of the sediments might be 

obscured by the effect of varia^ons of other factors in 

any individual group, and still more in a large number 

of groups. Consequently, if a consistent relationship 

between salinity and calcium carbonate is found for 

nearly all the groups, the chances are much in favor 

of its being a true relationship, though not necessarily 

one of cause and effect.

It seems evident, therefore, that if there is such a 

relationship for salinity, its existence will be indicated 

by a statistical study of this type, but it does not 

necessarily follow that the true degree of the relationship will be indicated. For example, as pointed out 

below, the extent to which the water is saturated with 

calcium carbonate may possibly be related to the surface 

salinity and thus may have influenced in part the relation between salinity and calcium carbonate content 

of the sediments brought out by the statistical study.

METHOD OF COMPARINO SALINITY AND CALCIUM 

CARBONATE CONTENT

In the determination of the relation of salinity to 

calcium carbonate, the samples likewise were classed 

according to groups. Each of the 32 groups for temperature, depth, and distance from shore was divided 

into 4 groups based on salinity and into 8 groups based 

on calcium carbonate content. The limits of the salinity groups, in parts per thousand, were less than 34, 34 

to 35, 35 to 36, and more than 36. This type of grouping was adopted because of the suggestion indicated 

by table 1 th.at the critical salinity was about 35 parts 

per thousand and that salinities of less than 34 or more 

than 36 parts did not seem to affect appreciably the 

calcium carbonate content of sediments. The limits 

of the calcium carbonate groups, in percent, were 0 to 

2, 2 to 5, 5 to 10, 10 to 20, 20 to 30, 30 to 50, 50 to 75, 

and more than 75. The object of this grouping was to 

separate the samples into varying grades of content 

of calcium carbonate, ranging from carbonate-free to 

limestone-forming sediments. The subsequent calculations, however, would have been simpler if the limits 

of the groups had been geometric instead of arbitrary.

It would also probably have been better if the average salinity and average temperature in the upper 200 

meters of water had been considered instead of the 

surface salinity and temperature. The statistical part 

of this report was prepared in 1931, primarily for the 

purpose of ascertaining whether or not the relationship 

expressed by table 2 was real. The papers of Wattenberg,28 Buch and others,29 and Mo berg and others,30 

which emphasize the importance of the upper 200 

meters of water with respect to the formation of calcium carbonate, had not yet appeared, and at that time 

there was no reason to presume that the average salinity 

or temperature of any particular depth zone would be 

better to consider than the surface salinity or temperature. In many parts of the sea—notably in low latitudes—the surface salinity represents the average 

salinity in the upper 200 meters of water more closely 

than the surface temperature represents the average 

temperature of that zone.31 The conditions in the 

upper 200 meters of water depend largely upon the 

circulation of water in the ocean. Heat derived from 

the sun raises the temperature of the surface water

28 Wattenberg, H., Kalziumkarbonat- und Kohlensa'uregehalt des Meerwassers: 

Wiss. Ergeb. Deutschen Atlantischen Exped. Meteor, 1925-27, Band 8, Teil 2, pp. 

1-333, 1933.

2« Buch, K., Harvey, H. W., Wattenberg, H., and Gripenberg, S., Ueber das 

Kohlensauresystem im Meerwasser: Conseil perm. expl. mer Rapports et procesverbaux, vol. 79, pp. 1-70,1932.

so Moberg, E. G., Greenberg, D. M., Revelle, R., and Alien, E. C., The buffer 

mechanism of sea water: Scripps Inst. Oceanography Bull., Tech. ser., vol. 3, no. 

11, 231-278, 1934. •

3i Defant, A., Die systematische Erforschung des Weltmeeres: Gesell. Erdkunde 

Berlin Zeitschr., Sonderband zur Hundertjahrfeier der Gesellschaft, p. 485, 1928. 

Wiist, G., Der Ursprung der Atlantischen Tiefonwasser: Idem, p. 520; Schichtungen 

und Tiefenzirkulation des Pazifisches Ozeans: Meereskunde VerofEentl., A, Heft 20, 

1929. Schott, G., Geographie des Atlantisches Ozeans, p. 144, Hamburg, C. Boysen, 

1926. Schott, G., and Schu, F., Die Warmeverteilung in den Tiefen des Stilles 

Ozeans: Annalen der Hydrographie, Band 38, pis. 2, 3, p. 48, 1910.
RELATION OF SALINITY TO CALCIUM CARBONATE CONTENT OF MARINE SEDIMENTS 283

more readily than it raises the salinity of the surface 

water by means of its effect on evaporation. These 

features may account in part for the apparently closer 

relation of the calcium carbonate content of the sediments to the surface salinity than to the surface 

temperature.

SOURCE OF DATA

About 3,000 samples were considered, of which 

1,953 were selected for study. The samples are 

described in Murray's Challenger?2 Pacific,33 and 

Atlantic 34 reports and in my report on source beds.35 

These publications give the calcium content, the depth, 

and the position of the samples. Pratje 36 and Correns 37 have published maps of the distribution of 

calcium carbonate in the South Atlantic, but the data 

from these maps were not used for the statistical study, 

because they were not presented in a form readily 

applicable to the statistical groups that were used.

The data for salinity were derived from Schott's 

map 3S showing the mean annual salinity of the surface 

of the oceans; and the data for temperature from maps 

by Schott,39 Schott and Schu,40 Knimmel,41 and 

Shokalsky,42 showing the mean annual isotherms of 

the surface water.

The samples available for study cover the world 

more or less satisfactorily. The Pacific and Atlantic 

Oceans are fairly well represented, but the Indian and 

Antarctic Oceans are not. No pelagic samples from 

the Arctic Ocean were available, but several samples 

were procured off the northern coast of Canada and 

Alaska. Most of the inland and semienclosed seas are 

represented—namely, the Arabian, Baltic, Bering, 

Black, Caribbean, Japan, Java, Mediterranean, Red, 

and Yellow Seas and the Gulfs of California, Maine, 

Mexico, Panama, and Venezuela. The near-shore 

samples came from many parts of the Arctic, Atlantic, 

and Pacific coasts of North and South America, the 

entire west coast of Africa, and the coasts of parts of 

Arabia, Antarctica, Australia, Europe, India, Japan, 

Java, and the Philippine Islands.

as Murray, J., and Renard, A. F., Challenger Kept., Deep-sea deposits, pp. 34-147, 

1891.

33 Murray, J., and Lee, G. V., The depth and marine deposits of the Pacific: 

Harvard Coll. Mus. Comp. Zoology Mem., vol. 38, pp. 40-148, 1909.

34 Murray, J., and Chumley, J., The deep-sea deposits of the Atlantic Ocean: 

Royal Soc. Edinburgh Trans., vol. 54, pp. 1-216,1924.

« Trask, P. D., Hammar, H. E., and Wu, C. C., Origin and environment of 

source sediments of petroleum, pp. 249-273, Houston, Tex., Gulf Publishing Co., 1932.

39 Pratje, 0., Geologische Tiefseeforschungen auf der Deutschen Atlantischen 

Expedition: Deutsche geol. Gesell. Monatsber., Band 79, p. 202, 1927.

« Correns, C. W., Mineralogisch-geologische Arbeiten der Deutschen Atlantischen 

Expedition: Gesell. Erdkunde Berlin Zeitschr., Jahrg. 1928, Erganzungsheft 3, p. 127.

38 Schott, G., Die Verteilung des Salzgehaltes im Oberfiacherwasser der Ozeane: 

Annalen der Hydrographic, Band 56, Heft 5, p. 184,1928.

39 Schott, G., Geographic des Atlantischen Ozeans, pi. 10, p. 144, Hamburg, C. 

Boysen, 1926.

« Schott, G., and Schu, F., Die Warmeverteilung in den Tiefen des Stillen Ozeans: 

Annalen der Hydrographie, Band 38, Heft 1, pp. 2-25, 44, 1910.

« Kriimmel, O., Handbuch der Ozeanographie, Band 1, pp. 400-406, 1907 (for 

Indian Ocean).

« Shokalsky, J., Oceanography [in Russian], pp. 134,135, Petrograd, 1917.

Some areas were represented by many samples, and 

others by few. In order to make the results of the 

statistical study of these areas comparable, the number 

of samples from areas represented by many samples 

was reduced. In this process of reduction, an attempt 

was made to select samples proportionately with respect to area, so that the sediments chosen for study 

would represent an approximately equal distribution. 

This process of elimination lowered the number of 

samples to 1,953, of which 928 were typically pelagic 

deposits and 1,035 were near-shore sediments or deposits from inland seas or lakes.

About 4 percent of the near-shore sediments represent samples of fresh-water and saline lakes that had 

been studied previously.43 The sediments of saline 

lakes contain considerable calcium carbonate, but those 

from nearly all the fresh-water lakes contain less than 

2 percent. It is probable, however, that the proportion 

of fresh-water lakes characterized by calcareous deposits is greater than was indicated by the previous 

work, which was based on relatively few lakes; and it 

is also probable that the calcium carbonate content of 

lacustrine sediments is ordinarily influenced more by 

other factors than it is by the salinity of the water. 44

The relation of the salinity to the calcium carbonate 

content of lacustrine sediments is not discussed in this 

paper, but in order to make the study of the effect of 

salinity representative of general conditions, a few 

lacustrine samples were included in the statistical 

study. As this paper is restricted mainly to the discussion of marine conditions, it might be better if this 

had not been done. The lacustrine samples, however, 

form so small a proportion of the total number of 

samples, and the relationships they exhibit are so similar to those indicated by marine sediments, that the 

statistical results are not significantly different from 

what they would have been if the lacustrine samples 

had been omitted.

METHOD OF COMPUTING DATA

The method of recording the data was to use 32 

cards, 16 for near-shore sediments and 16 for pelagic 

deposits. The 16 cards in each of these groups were 

divided into 4 series of temperature groups and 4 series 

of salinity groups. For example, there were 4 cards 

for the salinity group of less than 34 parts per thousand, 

1 for each of the 4 temperature subgrades. Similarly 

there were 4 cards for the salinity group of 34 to 35 

parts per thousand, 1 for each temperature grade; 

and so on. On each card the depth was plotted against 

the calcium carbonate content. Each of the 1,953 

samples was placed in the proper category on one of 

these cards. Table 3 illustrates the manner of plotting.

« Trask, P. D., Hammar, H. E., and Wu, C. C., op cit., pp. 100, 281.

44 Naumann, E., Die Bodenablagerungen der Seen: Internat. Ver. theor. u. 

angew. Limnologie Verb., Band 4, 1929. Pia, J., Die rezente Kalksteine; Min. 

pet. Mitt., Erganzungsband, 1933.
284 SHOETEE CONTEIBUTIONS TO GENEEAL GEOLOGY, 1936

TABLE 3.—Relation of calcium carbonate content of pelagic deposits to depth of water in areas in which the surface water has a salinity

greater than 36 parts per thousand and a temperature higher than 25° C.

CaCOa (percent)

Oto2 _______ ...._. ___ .... ___

2 to 5 _______ _ _ .__. _____ ._._

5 to 10_ _..._._____ __________ _.

10 to 20__. ...__._....__. -.-....._._

20 to 30___._.__. _______ . ___ ._

30to50__._ _ . _____ ___._._.__..

50 to 75_____.___ ____ -..._....____

75+ _._„.......... ........ __..____

Total.__.__.___ _ _____ _ -.__

Depth (fathoms)

0 to 500 500 to 1,000 1,000 to 

1,500

1,500 to 

2,000

2,000 to 

2,500

2,500 to 

3,000

3,000 to 

3,500

3,500 to 

4,000

Number of samples

2 

2

4

77

1

6

7 

79

1

8 

3

12 

66

1

5

7 

7

20 

62

1 

1 

1

9 

22 

12

46 

60

1

6 

2 

5

8 

4

7

33

28

9 

4 

3

1 

1 

2

20 

9

1

1

•

2

4

Total 

number of 

samples

11 

10

7 

7 

11 

21 

47 

30

144

47

The cards could just as well ha-ve been arranged in 

a form in which, the salinity or the temperature instead 

of the depth was plotted against the calcium carbonate 

content of the sediments, but the depth was used 

because of the time saved thereby in compilation.

In order to study the relationship of surface salinity 

and surface temperature to the calcium carbonate 

content of the sediments the figures on these cards were 

rearranged, on 64 other cards—32 for salinity and 32 

for temperature. The salinity and temperature groups 

were subdivided into near-shore and pelagic groups, 

and these in turn were segregated into four depth 

groups, each representing an interval of 1,000 fathoms. 

That is, for salinity there were 32 cards to cover all 

possible variations of two groups based on distance 

from shore, four temperature groups, and four depth 

groups. Similarly there were 32 cards for surface 

temperature, representing all possible combinations of 

two groups based on distance from shore, four depth 

groups, and four salinity groups. These 64 cards, 

together with the 32 cards that showed the relation of 

depth to calcium carbonate content, formed the basis 

for the statistical study of the problem.

ARITHMETIC MEANS 

METHOD OF PRESENTING DATA

It is not practicable to present in this paper the 96 

size distributions 4S represented by these cards. Instead, the significant features are summarized in three 

ways—first, in tables 4 to 6, which show the average 46 

calcium carbonate .content for different combinations 

of depth, surface salinity, and surface temperature; 

second, in figures 12 to 18, which show graphically the 

relation of the average calcium carbonate content of 

the sediments for given surface salinity, surface temperature, and depth; and third, in table 7, which indicates for each of the 96 subgroups the coefficients of 

correlation between the calcium carbonate content of 

the sediments and the salinity, the temperature, and 

the depth.

« A "size distribution" is a numerical classification of items according to a number 

of groups of different sizes. Table 3 represents the size distribution of calcium carbonate and depth for a particular temperature and salinity. It shows the distribution of the samples with respect to calcium carbonate and depth on the basis of the 

number of samples in each of several categories.

« "Mean" and "average" unless otherwise stated are used interchangeably in the 

present report to indicate the arithmetic mean.
RELATION OF SALINITY TO CALCIUM CARBONATE CONTENT OF MARINE SEDIMENTS 285

TABLE 4.—Mean calcium carbonate content of marine sediments for different salinity and temperature of the surface water and for

different depth of water; data arranged to show relation for depth

[Figures in italic are averages based on 5 samples or less; figures without indication of probable error represent single samples]

Near-shore sediments

Salinity (parts per thousand)

<34___________________

34 to 35. __ -.---._._..

35 to 36 ___ _---__.„.._

36+-------------------

Mean___ _______

Temperature (°C.)

roto io__ _ __.____-_

JlOto20--__--____-_.

UO to 25__-__. _______„ 

[25 to 30_----_---.____

fO to 10__ ___ __---_..

JlOto20. _ __________

)20to25_----__-______

[25 to 30-________.___

fOtolO_______________

JlO to20__-_--_-_-____

120 to 25 _ ___--_-.___

125 to30__---__--_-___

fOtolO_._-.__________

JlO to 20-__ __ ______

]20 to25_ __ ___ _ _

[25to30__----_--__-__

Depth (fathoms)

0 to 100 100 to 250 250 to 500 500 to 1,000 1,000 to 

1,500

1,500 to 

2,000

2,000 to 

* 3,000

3,000 to 

4,000

Mean percentage of calcium carbonate

6± 4 

7± 4 

3± 3 

19 ±13 

3± * 

3± 3 

13± 7 

14±18

30± 4 

45 ±21 

53±31

37 ±30

28± 9 

46 ±28

23 ±13

7± 4 

10± 8

24± 8 

1± 1 

15 ± f 

1± ? 

16±13 

• 20± 3 

41 ±13 

62± ? 

60 ±19

46 ±22

62 ±10

25 ±10

4± 1 

8± 8 

62± 5 

13± 7 

1± f 

16± 5 

12± 8 

26 ±18 

12± 3 

27 ±14 

39±15 

82± f

27± 9 

16± f 

57±18

24 ±10

3± 1 

15±10

88 ± 5 

12± 6 

14± 6 

17± 6 

12± 9 

18±10 

17± 7 

24 ± 9 

35 ±12 

S8±10

32±11 

1S± 7 

49 ±26

23± 9

3± 2 

20 ± 5 

62 ± f 

20± 6 

26± 6 

20 ±10

28 ±18

18± 6 

23± 8 

51±15

33 ±12

16± 6 

41 ±24

26± 9

10± 8

1± f

19±14

17± 4 

5± 1 

3± 2 

10± 8 

25 ± f 

19±11 

20± 9 

19±11

29± 5 

16± 4 

37 ±12

16± 8

1±0

6±3

13±8

4±2 

4±% 

9±7

11±6 

9±4 

16±6

29±5

24±9

12±5

1±0

l±f

1±0

Pelagic deposits

Salinity (parts per thousand)

<^O*-__-_---_-_-_-__-_-

34 to 35--._ _______ _

35 to36--_--_ _ _ _ ...

O_? f

Mean____________

Temperature (°C.)

fOto 10___.-____._____

JlO to 20. _ --___.___.

1 20 to 25 __ _-._-_____

[25 to 30 ___ _ ____ _

fOtolO_______________

JlOto20_--__ _________

120 to25_____-________

[25 to30-_-----_---___

fOto 10 ___ __.-______

JlO to20_ __ _________

]20 to25_---___-_-____

[25 to 30 _ ___________

fOto 10__ __ _________

JlOto20___.__________

)20 to25_-_-_-___-____

[25 to30_-._-________.

Depth (fathoms)

0 to 500 500 to 

1,000

1,000 to 

1,500

1,500 to 

2,000

2,000 to 

2,500

2,500 to 

3,000

3,000 to 

3,500

3,500 to 

4,000

Mean percentage of calcium carbonate

54±19

82± 4 

82± ?

75± 6 

77± 8

73± 9

40± f

62± f 

51 ± 7

48± 8 

57± 6 

65± 6

77± 5

63 ±13

74± 6 

77± 5

63± 7

36 '±83 

72± 7

62± 5 

62± ? 

25± f 

48 ±10

60± 8

82± ? 

74± 7

62±15 

76± 6 

66± 8

62 ±10

18± 9 

38 ±25

21 ±14 

77± 6 

71 ±12 

2± 1 

43 ±10

67±10

56± 7 

76± 6

68 ±12 

63 ±12 

62 ±16

53±10

1± 0

11± 8

33 ±20 

38 ±33 

_± 0 

51 ±19 

40±.t 

50±15 

40 ±30 

57±14

68 ±11 

58±11 

60 ±14

44±15

*± o

1± 0

49±11 

2± 1 

1± 0 

21 ±20

28 ±24 

39 ±30 

40 ±19

45 ±17 

32 ±21

28 ±18

25 ±15

-± f

1± 0

1± f

1± 0

18±11

40~± t 

4± 2 

9± 4

9± 4

1±0

l±f

l±f

4±2

2±1

The mean calcium carbonate content of each depth 

group for all combinations of surface salinity and 

temperature is shown in table 4. The figures for the 

probable error 47 given after the figure for the mean 

represent the semi-interquartile range 47 when more 

than 10 samples were averaged, and two-thirds the 

standard deviation 47 when less than 10 samples were 

averaged.

47 For detailed discussion of these statistical terms, see Chaddock, R. E., Principles 

and methods of statistics, pp. 153-163, 235-238, New York, Houghton Mifnin Co., 

1925.

The probable errors obtained in this way indicate 

only the order of magnitude of the scatter 48 of the 

items averaged. For example, in table 4 the mean 

representing the column for the depth group of 2,500 

to 3,000 fathoms in table 3 is given as 28±18 percent, 

which indicates that the calcium carbonate content of

48 The "scatter" is a measure of the deviation of the samples from the mean. For 

example, if the items in a size distribution range between 28 and 32 percent the 

maximum deviation from the mean (30 percent) is 2 percent, which is small; but if 

the items range between 10 and 50 percent the mean is still 30 percent, but the 

maximum deviation from the mean is 20 percent, which is large. The scatter in the 

first case would be small and in the second large.

92918—37———3
286 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1936

one-half the samples that were averaged lies within a 

range of 2X18=36 percent, distributed, on both sides 

of the mean of 28 percent. Actually, one-half tjie 

samples have a calcium carbonate content ranging 

between 8 and 44 percent; This average of 28 ±18 

in table 4 is not to be confused with the average of 

25 ±15 just below, which refers to the general average 

for all pelagic samples in the depth interval 2,500 to 

3,000 fathoms, regardless of temperature or salinity.

RESULTS

It is evident from table 4 that the calcium carbonate 

content of the sediments in general decreases with 

increase in depth of water, especially below 2,000 

fathoms. The amount of scatter, however, is high, 

which indicates that for this group of sediments the 

relationship is not close or that factors which have not 

been considered mask the effect of depth.

The relationship of surface temperature to the calcium carbonate content is illustrated better by table 5. 

This table was compiled from the 32 cards for temperature. The probable error was obtained in the same 

way as in table 4. The table indicates that the calcium 

carbonate content rises as the surface temperature 

increases. However, the amount of scatter, as shown 

by the figures for probable error, is high, which indicates that the relationship is to a certain extent 

indefinite.

A similar table for surface salinity could be compiled 

by a rearrangement of the items in table 5, and it would 

show a rise in calcium carbonate content for rise in 

salinity. However, as the relations for salinity are 

expressed in detail by figures 12 to 16, a table especially 

arranged to illustrate the effect of salinity was not 

prepared.

TABLE 5.—Mean calcium carbonate content of marine sediments for different salinity and temperature of the surface water and for

different depth of water; data arranged to show relation for temperature

[Italic figures represent averages based on 5 samples or less. Numbers without indication of probable error represent single samples]

Salinity (parts per 

thousand)

<34............. 

34 to 35. _________

35 to 36 ___ ._ _

O_3 1

Mean_____

Depth (fathoms)

fO to 1,000— ________

J 1,000 to 2,000... _ .

} 2,000 to 3,000. -..._.

13,000 to 4,000.. _ ..

ro to 1,000... ........

1 1,000 to 2,000--....

12,000 to 3,000... _ .

(.3,oooto4,ooo— -_-- rotol,ooo---__ _ __

1 1,000 to 2,000 _ . ..

12,000 to 3,000. .. — _ _

[3,000 to 4,000..---.-

fO to 1,000...- ______ _

1 1,000 to 2,000.. .... _

12,000 to 3,000-. _ .

[3,000 to 4,000.. — ...

Temperature (°C.)

Near-shore deposits

OtolO 10 to 20 20 to 25 25 to 30

Pelagic deposits

OtolO 10 to 20 20 to 25 25 to 30

Mean percentage of calcium carbonate

5±2 

8±7 

1±0 

1±0 

5±2 

21±6

14±5

25 ±?

9±4

9± 6

16± 5 

6± 3 

1± 1 

11± 6 

16±10 

4± 2

30 ±10 

19± 8

11± 6

33±11 

32± 9 

29± 5

17± 7

17±16

6%± f

12± 8

S± 2 

4± %

40 ±16 

22± 9 

9± 4

%2± 7 

16± 6

20± 9

17± 8 

20±12 

13± 8

21±15 

22 ±13 

9± 7

53 ±29 

44±13 

16± 6

50 ±25 

44 ±20

24± 9

28 ±14

40± 0 

21 ±15 

1± 0 

1± ? 

62± f 

71± 6 

42 ±19

57± 6

•40 ± f

40± 9

47 ±22

7± 4

51 ± 7 

68±12 

18± 9 

1± 0 

68± 6 

65 ±10 

43 ±21 

1± 0 

63±13 

65±13 

55±17 

40± f

45±11

6± 5 

1± 0

*± f 

82± f 

57±10 

40 ±30 

1± ? 

75± 6 

66±11 

44 ±22 

4± 2

36±11

21 ±14

49 ±14 

45 ±10 

37±26

1± f 

77± 5 

75± 6 

48 ±23 

18±11 

77± 6 

63±13 

47±18 

8± 4

46 ±13

A comparison of the relations for surface salinity, 

surface temperature, and depth is presented in table 6. 

Each number representing the percentage of calcium 

carbonate in this table is the average of two or more 

numbers in tables 4 and 5. In the process of averaging, 

in order to make the data in table 6 as comparable as 

possible, numbers in tables 4 and 5 based on five to two 

samples were weighted one-half and numbers based 

on only one sample were weighted one-fourth. The 

means shown at the bottom of each of the three main 

divisions of table 6 represent the average of all the 

numbers given for the particular grouping in tables 4 

and 5, not the average of the four or less averages representing the particular grouping in table 6. For example, the general average of the calcium carbonate 

content of the pelagic sediments in areas in which the 

surface salinity is less than 34 parts per thousand is 

given as 22 ± 12 in table. 6. This is not the mean of the 

two numbers (31 ± 18 and 5 ±3) given for this grouping 

in table 6; it is the mean of the seven numbers representing this grouping in table 5. It was hoped by this 

process of averaging to minimize irregularities caused 

by the small number of samples in some subgroups. 

However, because of the large probable error the averages indicated in tables 4 to 6 are to be considered as 

indicating only the order of magnitude.
RELATION OF SALINITY TO CALCIUM CARBONATE CONTENT OF MARINE SEDIMENTS 287

TABLE 6.—Comparison of the relation of the calcium carbonate content of marine sediments to the salinity of the surface water, the temperature of the surface water, and the depth of water, as indicated by arithmetic means

[Italic figures represent averages based on less than 5 samples. Numbers without indication of probable error represent single samples]

Temperature (°C.)

Oto 30... — --___

Mean......

Temperature (°C.)

Oto 10 __ . ______

10 to 20 __ . ______

20to25_..-_. _ _

25 to 30_. ________

Mean__ __

Depth (fathoms)

Oto4,000_________ 

Mean___ _

Depth (fathoms)

ro to i,ooo_. _..-____

1 1,000 to 2,000______

\ 2,000 to 3,000...____ 

[3,000 to 4,000. _ ...

Salinity (parts per thousand)

><34to36+.._ __ .

Salinity (parts per thousand)

f<34_______________

J34 to 35_. ..-..._.__

135 to 36 _____ ___

[36+..— __________

Salinity (parts per thousand)

Near-shore deposits

<34 34 to 35 35 to 36 36+

Pelagic deposits

<34 34 to 35 35 to 36 36+

. Mean percentage of calcium carbonate

13±9 

18±9

7±4

• i±o

12±7

12± 8 

17± 9 

6± 4

13± 7

34±15 

28 ±10

12± 5

28±11

37 ±14 

33 ±13

27± '7

33 ±14

31 ±18 

5± 3

22 ±12

53 ±12 

47± 8 

22±13 

*± 0

35±11

69± 6 

66± 9 

43 ±24

--± 7

50 ±12

72± 9 

65±12 

49 ±19 

10± 3

51±12

Depth (fathoms)

Near-shore deposits

0 to 1,000 1,000 to 2,000 2,000 to 3,000 3,000 to 4,000

Pelagic deposits

0 to 1,000 1,000 to 2,000 2,000 to 3,000 3,000 to 4,000

Mean percentage of calcium carbonate

r 9± 3

J 21± 8 

1 23±12 

[ 35±19

23±11

15± 7 

21± 9 

21 ± 6 

33 ±15

22±10

1±0

14±4

7±3 

15±7

12±5

l±f

1±?

54±6 

63±9

77±7 

66±9

66±7

46 ±10 

61 ±14 

43± 9 

56 ±10

57±11

25 ±10 

31 ±13 

34±17 

44 ±22

35±17

9±f 

3±2 

12±8

7±4

Temperature (°C.)

Near-shore deposits

Oto 10 10 to 20 20 to 25 25 to 30

Pelagic deposits

Oto 10 10 to 20 20 to 25 25 to 30

Mean percentage of calcium carbonate •

4±3 

13±4 

16±5

9±4

9±5 

10±6 

22±8 

31±9

17±7

S8±18 

8± 5 

26 ±10

19± 7

20± 9

17± 9 

17±12 

42 ±16 

39 ±18

28±14

17±10 

62 ±10

49± 6

40± 9

27±13 

37± 8 

50±11 

58±14

45±11

3± 3 

47 ±20 

47±11

36±11

*1±14 

40 ±16 

52 ±12 

49 ±10

46 ±13

Table 6, like tables 4 and 5, exhibits a rise in calcium 

carbonate content of the sediments as the surface 

salinity and surface temperature increase and as the 

depth decreases. Because the averages are based on 

more samples than in tables 4 and 5, the respective 

relationships of salinity, temperature, and depth to 

calcium carbonate content are more regular.

GRAPHIC PRESENTATION 

METHOD OF PLOTTING

Although most of the essential features of the statistical study of the data are presented in tables 4 to 6, 

the general relations are illustrated more clearly by 

diagrams. Figures 12 to 18 represent the main features given in these tables. Figures 12 to 15 show 

the relation of surface salinity to the calcium carbonate 

content of the sediments for different combinations of

depth of water and surface temperature. These figures are based on the means shown in table 5. Size 

groups in which the mean was based on only one sample are not represented in the figure^. In the preparation of the figures, the averages of the groups representing salinities less than 34 and more than 36 parts 

per thousand were arbitrarily taken as 33.5 and 36.5, 

respectively.

RELATION FOR SALINITY

Figure 12 shows the relations for salinity in areas 

in which the surface temperature ranges between 0° 

and 10° C., for two depth intervals of both near-shore 

and pelagic deposits. The number of samples was 

insufficient to illustrate the relation for the other depth 

intervals in this temperature group. The calcium 

carbonate content for each depth interval represented
288 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1936

on this figure rises with increase in salinity. In the 

near-shore deposits in the depth interval 0 to 1,000 

fathoms the mean calcium carbonate content rises 

from 5 percent for salinities less than 34 parts per

s

I 20

SALINiTY, PARTS PER THOUSAND 

36 ___ 37 33 34

NEAR-SHORE GROUP PELAGIC GROUP

Depth groups 

—— 1000-2000 fathoms

FIGURE 12.—Relation of calcium carbonate content of marine sediments to the salinity of the surface 

water for temperatures of 0° to 10° O. In this and the next four figures the lines represent mean calcium 

carbonate content of the sediment for the given salinity of the surface water, for water of different 

depths. The depths are classified into four groups of 1,000 fathoms each, and each depth group is 

represented by one line—for example, the dashed line for the 0-1,000 fathom group refers to all areas in 

which the water ranges in depth between 0 and 1,000 fathoms. This figure represents all areas in which 

the mean annual temperature of the surface water is between 0° and 10° C.; figures 13, 14, and 15 refer 

respectively to areas in which the temperature is 10° to 20°, 20° to 25°, and 25° to 30° C.; and figure 

16 refers to the average of the four temperature groups—that is, to all areas, regardless of temperature.

thousand to 14 percent for salinities ranging between 

35 and 36 parts; and in the interval 1,000 to 2,000 

fathoms from 8 percent for salinities less than 34 parts 

per thousand to 21 percent for salinities ranging between 

34 and 35 part^'. In the pelagic group, for 

the depth interval of 1,000 to 2,000 fathoms, the mean calcium carbonate content 

rises from 21 percent for salinities less than 

34 parts per thousand to 71 percent for 

salinities between 34 and 35 parts; and in 

the interval 2,000 to 3,000 fathoms it 

rises from 1 to 42 percent between these 

salinity limits.

The pelagic deposits contain more calcium carbonate than the near-shore deposits. In the near-sjiore group the sediments 

in the interval 1,000 to 2,000 fathoms have 

a greater calcium carbonate content than 

those in the interval 0 to 1,000 fathoms, 

thus presumably reflecting the effect of 

masking on the calcium carbonate content 

by terrigenous detritus. In the pelagic 

group the sediments in the interval 1,000 to 

2,000 fathoms contain more calcium carbonate than those in the interval 2,000 to 3,000 fathoms, 

thus presumably representing the effect of solution of 

particles as they fall to the bottom in deep water.

The same phenomena apply to the temperature 

group 10° to 20°, illustrated by figure 13. The calcium

carbonate content for each depth interval, except the 

interval 3,000 to 4,000 fathoms, which is represented 

by only a few samples, rises with increase in surface 

salinity. However, in the pelagic sediments from 

intervals of 0 to 1,000 and 1,000 to 2,000 

fathoms the calcium carbonate content is 

approximately constant for a salinity in 

excess of 35 parts per thousand. It is 

greater for the pelagic group than for the 

near-shore group, and it is greater for 

depth intervals of less than 2,000 fathoms 

than for intervals of more than 2,000 fathoms. The calcium carbonate content of 

the sediments in the interval 0 to 1,000 

fathoms is approximately equal to that in 

the interval 1,000 to 2,000 fathoms for 

both the near-shore and the pelagic groups, 

but in both depth intervals it is distinctly greater in the pelagic than in the 

near-shore group.

The calcium carbonate content of the 

sediments in the temperature group 20° 

to 25°, illustrated by figure 14, in general 

increases from low to high salinity. The 

increase, however, is more consistent for 

the pelagic than for the near-shore group. 

In the interval 20° to 25°, as in that from 

10° to 20°, the increase in calcium carbonate content of pelagic sediments is slight as the salinity rises above 35 parts per thousand. The decrease 

with increasing depth is well illustrated by this temperature interval, for both near-shore and pelagic sediments.

2000-3000 fathoms

SALINITY, PARTS PER THOUSAND 

36 37 33 34

1-

0

D_

CONTEN 0 C

CO

o:

o

2

0

u 

o

—-

/'

/ .x'

^-' x

•*" ~* ^^

^Xx

/

/

'''

\s~~~

/'

'

/

s''

^^^

f

/

•^^

'''

n

NEAR-SHORE GROUP PELAGIC GROUP

Depth groups 

_ — — — 01000 fathoms ______ 2000 3000 fathoms

_______ 1000-2000 fathoms ——.——. 3000-4000 fathoms

FIGURE 13.—Relation of calcium carbonate content of marine sediments to the salinity of th» surface 

water for temperatures of 10° to 20° C. (See fig. 12 for explanation.) .

The calcium carbonate content of sediments of the 

temperature group 25° to 30°, illustrated by figure 15, 

in general increases as the salinity rises. The increase 

here, as in the lower-temperature groups, is small above 

a salinity of 35 parts per thousand. In fact, in two of
RELATION OF SALINITY TO CALCIUM CARBONATE CONTENT OF MARINE SEDIMENTS 289

the seven groups shown in figure 15, the mean calcium 

carbonate content decreases significantly as the salinity 

rises above 35 parts.

This figure illustrates well the loss in calcium carbonate content with increase in depth. The decrease 

is small above 2,000 fathoms and large 

below 2,000 fathoms. The pelagic deposits contain more calcium carbonate 

than the near-shore sediments.

The calcium carbonate content of all 

groups above 3,000 fathoms, represented 

in figures 12 to 15, rises with increase 

in salinity, but in one of the two groups 

for the interval 3,000 to 4,000 fathoms 

it decreases as the salinity rises above 

35 parts per thousand, and in the other 

it is constant between salinities of 34 

and 36 parts per thousand, which represent the limits of the samples available. This rise in calcium carbonate 

content for increased salinity for depths 

less than 3,000 fathoms is so consistent 

in so many different.groups of temperature and depth that it seems evident 

. that surface salinity is definitely related 

to the calcium carbonate content of the sediments.

A summary of all the temperature groups illustrated 

by figures 12 to 15 is presented in figure 16, which is 

based on table 6. The heavy broken line in this figure 

represents the average of all the depth groups shown

The rate of increase of calcium carbonate with respect 

to salinity apparently decreases as the salinity rises 

above 35 parts per thousand, as indicated by the 

flattening of the general curves for both the near-shore 

and pelagic groups for salinities greater than 35 parts.

SALINITY, PARTS PER THOUSAND 

36_______3_7 33

'/-

\

NEAR-SHORE GROUP

0-1000 fathoms

Depth groups 

—— 1000-2000 fathoms

PELAGIC GROUP

______ 2000-3000 fathoms

FIGURE 14.—Relation of calcium carbonate content of marine sediments to the salinity of the surface water 

for temperatures of 20° to 25° C. (See fig. 12 for explanation.)

The increase in calcium carbonate between salinities of 

34.5 and 35.5 parts per thousand is 15 percent, compared with 5 percent between 35.5 and 36.5 parts in 

the near-shore sediments and with 1 percent for the 

same interval in the pelagic sediments.

SALINITY, PARTS PER THOUSAND 

36 37 33 34

RELATION FOR DEPTH

80

NEAR-SHORE GROUP PELAGIC GROUP

Depth groups 

— — — — 0-1000 fathoms ______ 2000-3000 fathoms

_______. 1000-2000 fathoms __ - ___ 3000-4000 fathoms

FIQTJBE 15.—Relation of calcium carbonate content of marine sediments to the salinity of the surface water for 

temperatures of 25° to 30° C. (See fig. 12 for explanation.)

and is based on the general means given for salinity 

in table 6. This figure shows the general increase 

in calcium carbonate content with rise in salinity. 

The average calcium carbonate content for all temperatures and all depths, in the near-shore group, 

increases from 12 to 33 percent with the increase from 

low to high salinity, and in the pelagic group it increases from 22 to 51 percent.

Figure 16 shows also the decrease in 

calcium carbonate content of the sediments as the depth increases. The two 

lines for the depth intervals above 2,000 

fathoms are close together, and those for 

the depth intervals below 2,000 fathoms 

are relatively far apart. This feature 

indicates that the loss in calcium carbonate with increasing depth is greater below 

than above 2,000 fathoms.

The loss with increasing depth is illustrated better by figure 17, which shows 

the relation of depth to calcium carbonate for various salinities. Each salinity 

curve in this figure represents the average of the four temperature groups for 

the particular salinity and is based on 

data presented in table 4.

In the pelagic sediments the rate of 

decrease of calcium carbonate with respect to depth is 

fairly, regular for all depths, although it is slightly less 

above 2,000 fathoms than below 2,000 fathoms. In the 

near-shore deposits, however, the rate of decrease with 

respect to depth is distinctly less above 1,500 fathoms 

than below 1,500" fathoms. This feature is indicated 

by the increase in the slope of the curve for the general 

average at a depth of about l,500_fathoms.
290 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1936

In fact, in the near-shore group the mean calcium 

carbonate content for all salinities and temperatures 

is nearly constant between depths of 0 and 1,500 fathoms. The average calcium carbonate content for

SALINITY, PARTS PER THOUSAND 

36 37 33 34

NEAR-SHORE GROUP

Depth groups 

—— 1000-2000 fathoms

PELAGIC GROUP

.. — 3000-^000 fathoms General average

2000

FIGURE 16.—Relation of calcium carbonate content of marine sediments to the salinity of the surface 

water; average for all temperatures. (See fig. 12 for explanation.)

depth intervals of 0 to 1,000, 1,000 to 2,000, 2,000 to 

3,000, and 3,000 to 4,000 fathoms for the near-shore 

sediments is 23, 22, 12, and 1 percent, respectively; 

for the pelagic deposits, 66, 57, 35, and 7 percent. 

The curves shown in figure 17 illustrate also the large 

calcium carbonate content for high 

salinity in pelagic deposits compared 

with near-shore deposits.

RELATION FOR SURFACE TEMPERATURE

The relation of the surface temperature to the calcium carbonate content of 

sediments is illustrated by figure 18, 

which is based on data presented in tables 

5 and 6. The figure shows that the calcium carbonate content of the sediments 

in general increases as the temperature 

rises. The rate of increase, however, is 

more regular for near-shore than for pelagic deposits. In the near-shore sediments the general average for all depths 

and salinities increases from 9 percent in 

the temperature group 0° to 10° to 28 

percent in the group 25° to 30°, and in 

the pelagic deposits it rises from 40 to 

46 percent between these two temperature groups. The rate of increase in the 

near-shore sediments is fairly regular, but in the pelagic 

sediments it is irregular, and the curve showing the relationship is W-shaped. The average calcium carbonate 

content of the four temperature groups 0° to 10°, 10° to 

20°, 20° to 25°, and 25° to 30° for the pelagic sediments 

is 40, 45, 36, and 46 percent, respectively. It would 

seem, therefore, that in the pelagic group the calcium

carbonate content of the sediments is less closely 

related to surface temperature than to surface salinity. 

In the near-shore group, however, as indicated by 

figures 16 and 18, the relation for surface temperature 

seems to be about as definite as the rela36 3? tion for surface salinity.

COEFFICIENTS OF CORRELATION

The curves in figures 12 to 18 represent 

means, but they do not show the amount of 

scatter. The scatter, however, is indicated 

in tables 4 to 6 by the figures representing 

the probable error. In general the scatter 

is high, which suggests that the relationship may not be as definite as is indicated 

by the averages shown in figures 12 to 18. 

The Pearsonian coefficient of correlation 

r 49 takes into consideration the amount 

of scatter and gives an objective value of 

the degree of relationship, or more properly the degree of association,50 between two 

components of a size distribution.

The coefficient of correlation is a ratio 

ranging between —1.0 and +1.0. If it is 

more than 0.7 the degree of association is very good; if it 

is between 0.5 and 0.7 the degree of association is good; 

if it is between 0.3 and 0.5 the degree of association is 

fair; and if it is below 0.3 the degree of association is poor. 

Negative coefficients indicate inverse relationships.

2000-3000 fathoms

DEPTH IN FATHOMS 

3000 4OOO 0

NEAR-SHORE GROUP PELAGIC GROUP

thousand — — — — — 35 to 36 parts per thousand 

General average

FIGURE 17.—Relation of calcium carbonate content of marine sediments to the depth of water. The lines in 

this figure represent mean calcium carbonate content of the sediments for the given depth of water in areas 

of different salinity of the surface water. The salinity is classified according to four groups, and each 

salinity group is represented by one line. Temperature is not considered in this figure; each line 

represents the average for all temperatures in the particular salinity group.

The coefficient of correlation is determined with a 

certain amount of unreliability, which is called the 

probable error. The probable error is greatest when 

the coefficient is 0, and it decreases in magnitude as the

*> Chaddock, R. E., Principles and methods of statistics, pp. 266-305, New York, 

Houghton Mifflin Co., 1925.

w The term "association" seems better than "relationship", because it implies no 

cause and effect relation.
RELATION OF SALINITY TO CALCIUM CARBONATE CONTENT OF MARINE SEDIMENTS 291

coefficient approaches 1.0 or —1.0. It also decreases 

as the number of samples increases. A coefficient of 

correlation ordinarily is not regarded as significant 

unless it is at least four times as great as the probable

error. Thus if the coefficient and the probable error 

are 0.30 ±0.10 the relation may not be significant, but 

if they are 0.30 ± 0.04, the relation, or rather the degree of 

association, though not particularly good, is significant.

TABLE 7.—Comparison of the relation of the calcium carbonate content of marine sediments to the salinity of the surface water, the 

temperature of the surface water, and the depth of water, as indicated by coefficients of correlation

Near-shore deposits

Salinity

Temperature (° C.)

0-10-___-_ __

10-20__. ______

20-25_________

25-30______.._

General 

average_

Depth (fathoms)

f 0-1, 000 

1 1, 000-2, 000 

1 2, 000-3, 000 

[3, 000-4, 000 

f 0-1, 000 

1 1, 000-2, 000 

1 2, 000-3, 000 

13, 000-4, 000 

f 0-1, 000 

1 1, 000-2, 000 

] 2, 000-3, 000 

[3, 009-4, 000 

f 0-1, 000 

1 1, 000-2, 000 

1 2, 000-3, 000 

[3, 000-4, 000

Coefficient of 

correlation

a 31 ±0.04

. 45 ± .08

. 56± .03 

. 37± .08 

.76± .06

. 28± . 07 

.38± . 11 

.50± . 18

.48± .03 

. 39± .06 

.39± . 11

. 44± . 02

Number of samples

190 

48 

11 

3 

234 

55 

24 

1 

85 

29 

8 

0 

233 

78 

26 

0

« 1,025

Depth

Temperature 

(°C.)

0-10 

10-20 

20-25 

25-30

Salinity 

(parts 

per thousand)

f <34 

134-35 

1 35-36 

I 36+ 

f <34 

1 34-35 

135-36 

I 36 + 

f <34 

J 34-35 

1 35-36 

I 36 + 

f <34 

1 34-35 

1 35-36 

I 36+

Coefficient of 

correlation

-0 07±0. 05

- 75± 06 

09 ± 12

- 21 ± 07 

- 29± 08 

31 ± 07 

14± 07 

- 84± 04 

26 ± 13 

27 ± 09 

38 ± 12 

03 ± 08 

02 ± 07 

21 ± 09 

09 ± 07

. 01 ± .06

Number of samples

184 

23 

• 31 

0 

96 

36 

78 

79 

24 

24 

44 

22 

76 

103 

47 

85

6 952

Temperature

Depth (fathoms)

0-1, 000 

1, 000-2, 000 

2, 000-3, 000 

3, 000-4, 000

Salinity 

(parts 

per thousand)

f <34 

134-35 

1 35-36 

I 36 + 

f <34 

134-35 

135-36 

I 36 + 

f <34 

134-35 

1 35-36 

I 36 + 

f <34 

1 34-35 

1 35-36 

I 36 +

Coefficient of 

correlation

0. 36 ±0. 03 

. 17± .06 

.45± .04 

. 38± . 05 

.40± .07 

. 02± .09 

.50± .07 

.20± . 11 

.68± .08 

. 31 ± . 13 

. 18± . 20 

-. 31 ± .17 

.00± . 34

. 32± .04

Number of samples

317 

131 

144 

150 

63 

55 

56 

36 

23 

23 

11 

12 

4 

0 

0 

0

1,025

Pelagic deposits

0-10__. _______

10-20_--._____

20-25. __ _ _ _

25-30____.__._

General

f 0-1, 000

1 1, 000-2, 000

)2,000-3,000

1 3, 000-4, 000

f 0-1, 000 

J 1, 000-2, 000

1 2, 000-3, 000 

[3, 000-4, 000 

f 0-1, 000

J 1, 000-2, 000

1 2, 000-3, 000 

13, 000-4, 000 

( 0-1, 000

1 1, 000-2, 000

1 2, 000-3, 000 

[3, 000-4, 000

0 47±0. 21

79± .07

65± .12

04± . 12 

19d? .06

58± .03 

77 ± . 10 

- 24± . 21

63± .05

32± .05

29± .22 

67 ± .08

50± .05

05± .05 

- 19± . 11

.45± .06

6

15

11

1

33 

133

165 

8 

9

63

Id5 

8 

23

86

200 

32

928

0-10

10-20

20-25

25-30

{

^"IA

34-35

36 +

f <34 

J 34-35

135-36 

I 36+ 

f <34

J 34-35

|o5-db 

I 36 +

( ^"IA

1 34-35

I o5-db 

I 36 +

0. 48 ±0. 14

. 35± .17

. 62 ± .08 

.49± .07

.48± .05 

. 32± .05

.59± . 10

. do± .08

.68± .03

.36± .07

. 52± .05 

. 71 ± .03

. 50± .03

14

12

1

0

26 

50

117 

113 

0

18

54 

134 

2

76

107 

133

C 857

0-1, 000

1, 000-2, 000

2, 000-3, 000

3, 000-4, 000

{

^"IA

34-35

d5-oo

36 +

f <34 

J 34-35

I o5-oo 

I 36 + 

f <34

J 34-35

I o5-oo 

I 36+ 

f <34

1 34-35

135-36 

I 36 +

-0. 18±0 20

. 58± 10

. 18± 10

.30± 15

-. 55 ± 07

. oU± Ub 

-. 04 ± 06 

.20± 13

. 28± 06

. 13± 05 

-. 10 ± 05

. 00± 25

.47± 15 

-. 21 ± 12

. 13± .05

1

11

19

40

17 

50

95 

135 

24

99

216 

1

7

. \.&

29

928

1 Total number of samples. * Depths greater than 2,000 fathoms excluded. 1 Depths less than 1,000 fathoms excluded.

The coefficient of correlation was determined for 

each of the 96 original size distributions except for a 

few that were represented by a small number of samples. 

The results are shown in table 7. The coefficients 

varied so much that in the determination of the general averages, four types of averages—the mean, the 

median, a weighted mean, and a weighted median— 

were averaged together to determine the general 

average. In the computation of the weighted averages 

the coefficients were weighted inversely as the probable 

error. The probable error of the averages represents 

the semi-interquartile range divided by the square root 

of the number of groups averaged.

The average coefficient of correlation of the 11 nearshore groups showing the relation of surface salinity 

to calcium carbonate content is .44±.02. The range 

is from .28±.07 to .76±.06. These data indicate a 

definite but not particularly close association between 

the calcium carbonate content of near-shore sediments 

and the salinity of the surface water. The average 

coefficient of correlation between surface salinity and 

calcium carbonate content of the 15 groups of pelagic 

sediments is .45±.06. The range is from —.24±.21 

to .79±.07. The numerical value of the average 

coefficient of correlation is nearly the same as for the 

near-shore deposits, but the larger probable error for
292 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1936

the pelagic group indicates that the degree of association is less certain for pelagic deposits than for nearshore deposits.

The average coefficient of correlation between depth 

and calcium carbonate content for the 15 groups of 

near-shore deposits is .01 ±.06, and for the 12 groups 

of pelagic deposits it is .50± .03. The smallness of the 

coefficient for the near-shore deposits indicates that 

they show no apparent relationship between depth and 

calcium carbonate content, but the figure for the 

pelagic deposits indicates a fairly good degree of asso80

60

540 •z.

o

§20

10°

TEMPERATURE CENTIGRADE 

20°__' 30° 0 __10° 20 30

20

NEAR-SHORE GROUP

Depth groups

— — — — 0-1000 fathoms - 

_ _ _ _ __ 2000-3000 fathoms __ .

PELAGIC GROUP

1000-2000 fathoms

- - ——— — 3000-4000 fathoms 

General average

FIGURE 18.—Relation of calcium carbonate content of marine sediments to the temperature of the surface 

water. The lines in this figure represent mean calcium carbonate content of the sediments for the given 

temperature of the surface water in water of different depths. The depths are classified according to four 

depth groups, as in figures 12 to 16. The salinity is not considered in this figure; each line represents the 

average for all salinities in each particular depth group.

ciation between depth and calcium carbonate content. 

The average coefficient of correlation between surface 

temperature and calcium carbonate content for the 13 

near-shore groups is .32±.04, which indicates at best 

only a slight degree of association; for the 14 pelagic 

groups it is .13±.05, which indicates very little 

association.

SIGNIFICANCE OF STATISTICAL DATA

The coefficient of correlation does not demonstrate 

a cause and effect relationship. Neither does a low 

coefficient necessarily indicate lack of relationship, as 

a small coefficient may be due to the effect of variables 

other than the two variables upon which the coefficient is based—that is, the real relationship may be 

masked by the effect of other factors. Such, for 

instance, might be the cause of the apparent poor

relationship between depth and calcium carbonate 

content in near-shore deposits, where the quantity of 

terrigenous detritus may obscure the effect of depth. 

A large coefficient, on the other hand, suggests strongly 

that there is a relationship.

The relation between the surface salinity and the 

calcium carbonate of sediments seems to be fairly 

definite, because the average coefficient for all the 

groups is about .45. The relation, however, is more 

definite for near-shore than it is for pelagic deposits 

because of the larger probable error for the pelagic 

deposits. The relation between depth 

and calcium carbonate content for pelagic deposits, but not for near-shore 

deposits, likewise is fairly definite. 

The relation for surface temperature, 

on the other hand, seems to be less 

certainly established. The apparent 

lack of relationship between surface temperature and the calcium carbonate content of the sediments, however, does 

not necessarily indicate a poor relation 

for temperature in general, because calcium carbonate is presumably formed 

chiefly in the upper 50 or 100 meters of 

water in the sea, and lateral variations 

in temperature in this zone do not necessarily occur in the same way as in the 

surface water above.

The statistical data therefore must be 

interpreted as not demonstrating the 

existence of a relationship between temperature and calcium carbonate content 

of the sediments; but they most certainly 

do not indicate that no relationship 

exists. In fact, the averages represented 

by figure 18, although associated with a 

large amount of scatter, suggest that 

the calcium carbonate content of marine 

sediments increases as the surface temperature of 

the overlying water rises.

The most definite conclusion derived from this statistical study is that the calcium carbonate content of the 

sediments seems to be definitely related to the salinity of 

the overlying surface water; the calcium carbonate content of the sediments increases with the surface salinity. 

The increase in calcium carbonate content of the 

sediments is greatest between salinities of 34 and 36 

parts per thousand. Sediments in areas where the 

salinity is less than 34 parts in general contain le'ss 

than 5 percent of calcium carbonate, and those in 

areas in which the salinity is more than 36 parts as 

a rule contain more than 50 percent of calcium carbonate. The calcium carbonate content increases but 

slightly as the salinity rises above 36 parts. The critical 

salinity seems to be about 35 parts per thousand, which 

is approximately the average salinity of the ocean.
EELATION OF SALINITY TO CALCIUM CARBONATE CONTENT OF MAEINE SEDIMENTS 293

AREAL RELATIONS OF CALCIUM CARBONATE CONTENT 

OF SEDIMENTS

PREPARATION OF MAP

In order to ascertain the extent to whieh the relationships of calcium carbonate to surface salinity, 

surface temperature, and depth might .be affected by 

extraneous factors, a map was prepared showing the 

distribution of calcium carbonate in marine sediments 

throughout the world with respect to depth of water 

and surface salinity (pi. 71). The surface temperature 

should also be shown on this map, but in order to 

make the map clearer the temperature was indicated 

on another map (fig. 19). The surface Salinity was 

also shown on figure 19, so that the relation of the 

temperature to the calcium carbonate content of the 

sediments could be ascertained easily by comparison 

with the salinity lines on the two maps.

SOURCE OF DATA

The salinities shown on plate 71 and figure 19 are 

taken from Schott 51 and the temperatures shown on 

figure 19 from Shokalsky.52 The depths are taken from 

Murray and Hjort,53 except those in the south Atlantic, 

which are based largely on Wust.54 The depth contours on "Wust's map are given in kilometers, which, 

although rou-ghly equal to multiples of 500 fathoms, 

cause difficulty in the construction of a map based 

on fathoms, especially in regions such as the ocean 

off southern Brazil, where a large area lies between a 

depth of 2,000 fathoms and 4 kilometers.

The distribution of calcium carbonate was compiled

from three sources—(1) the calcium carbonate con-

*tent of nearly 4,000 samples reported by several

workers; 55 (2) maps of the area! distribution of calcium

carbonate in the Pacific Ocean by Murray and Lee,56

61 Schott, G., Die Verteilung dqg Salzgehaltes im Oberflficherwasser der Ozeane: 

Annalen der Hydrographie, Band 56, Heft, 5, p. 184,1928.

52 Shokalsky, 3., Oceanography fln Russian], pp. 134-135, Petrograd, 1917. See 

also Schott, G., Geographic des Atlantischen Ozeans, pi. 10, p. 144, Hamburg, C. 

Boysen, 1926. Schott, G., and Schu, F., Die Warmeverteilung in den Tiefen'des 

Stillen Ozeans: Annalen der Hydrographie, Band 38, Heft 1, p. 44,1910. Krummel, 

O., Handbuch der Ozeanographie, Band 1, pp. 400-406,1907.

« Murray, 3., and Hjort, 3., The depths of the ocean, p. 128, New York, Macmillan Co., 1912.

** Wust, G., Schichtung und Zirkulation des Atlantischen Ozeans: Wiss. Ergeb. 

Deutschen Atlantischen Exped. Meteor, 1925-27, Band 6, Lief. 1, p. 84,1933.

48 Von Gimbel, Geologisch-mineralogische Untersuchung der Meeresgrundproben 

aus der Nordsee: Ergebn. Untersuchungsfahrten S. M. Knbt. Drache in der Nordsee, 

1881, 1882,1884, pp. 23-47, Berlin, 1886. Murray, J., and Renard, A. P., Challenger 

Rept., Deep-sea deposits, pp. 34-147,1891. Murray, J., arid Philippi, E., Die Grundproben der Deutschen Tiefsee Expedition: Wiss. Ergeb. Deutschen Tiefsee Exped. 

Valdivia, 1899-1900, pp. 98-136, 1908. Murray, J., and Lee, G. V., The depth and 

marine deposits of the Pacific: Harvard Coll. Mus. Comp. Zoology Mem., vol. 38, 

pp. 40-148, 1909. Philippi, E., Die Grundproben der Deutschen Siidpolar-Expedition: Deutschen Sildpolar-Exped., 1901-3, Repts., vol. 2, pp. 437-557, 1910. §pethmann, H., Studien ilber die Bodenzusammensetzung der Baltischen Depression 

vom Kattegat bis zur Insel Gotland: Wiss. Meeresuntersuchungen, neue Folge, 

Band 12, Abt. Kiel, pp. 309-312,1910. Murray, J., and Chumley, J., The deep-sea 

deposits of the Atlantic Ocean: Royal Soc. Edinburgh Trans., vol. 54, pp. 1-216, 

1924. Samoiloff, J. V., and Gorshkova, T. I., The deposits of the Barents and Kara 

Seas [in Russian, with English summary]: Trudy Plovuchnevo Morskovo Nauchnovo Inst. Vyp. 14, pp. 36-39,1924. Pratje, O., Die Sedimente der Deutschen Bucht: 

Wiss. Meeresuntersuchungen, neue Folge, Band 18, Abt. Helgoland, Heft 6, p. 126,

1931. Trask, P. D., Hammar, H. E., and Wu, C. C., Origin and environment of 

source sediments of petroleum, pp. 249-273, Houston, Tex., Gulf Publishing Co.,

1932.

*« Murray, J., and Lee, G. V., op. cit., map 3, p. 169.

in the north Atlantic south of latitude 25° by Correns,67 

and in the south Atlantic by Pratje; 58 and (3) maps of 

the distribution of the deep-sea deposits in the Atlantic 

and Indian Oceans by Murray and Philippi,69 in the 

Pacific Ocean by Murray and Lee,60 and in the northwest Pacific by Hanzawa.61 The data from all these 

sources were placed on a single map, and the lines of 

equal calcium carbonate content shown on plate 71 

were drawn upon the basis of the data so plotted.

CLASSIFICATION OF DATA

On plate 71 the calcium carbonate content of the 

sediments is separated into three groups—50 to 100 

percent, 10 to 50 percent, and 0 to 10 percent. If 

sufficient data were available it would be desirable to 

make more subdivisions, but as several large areas 

were represented only by a few bottom samples it 

seemed practicable to make only three groups. Furthermore, in many areas the calcium carbonate content 

of the sediments changes from high to low within a 

short distance; consequently, because of the relatively 

small scale of the map, it would be confusing to increase 

the number of subdivisions in these areas.

The threefold classification presented here separates 

the sediments into groups of rich, intermediate, and 

poor calcium carbonate content, or, in terms of rocks 

which the sediments would form when lithified, into 

(1) limestones, (2) calcareous shales or sands, and (3) 

slightly calcareous or noncalcareous shales or sands.

RETJABILJTY OF MAP

The distribution of calcium carbonate has been 

indicated over the entire map, but as many areas are 

represented by only a few data the map should be 

interpreted with an understanding of the conditions 

under which it was made.

In the Atlantic Ocean the mapping is based on a 

large number of samples and is fairly reliable between 

40° N. and 40° S. In the Pacific, however, it is based 

on fewer samples than in the Atlantic. Murray and 

Lee .present a map of the distribution of calcium 

carbonate in the Pacific, but their map contains large 

areas unrepresented by samples. Hanzawa 62 and 1 63 

present additional data, but stall several large areas are 

represented by only a few samples—notably north of 

40° N., south of 50° S., and in the southwest Pacific 

south of 20° S.

" Correns, C. W., Mineralogisch-geologische Arbeiten der Deutschen Atlantischen 

Expedition: Gesell. Erdkunde Berlin Zeitschr., Jahrg. 1928, Erganzungsheft 3, 

p. 127.

«8 Pratje, O., Geologische Tiefseeforschungen auf der Deutschen Atlantischen 

Expedition: Deutsch geol. Gesell. Zeitschr., Monatsber., Band 79, p. 202,1927.

59 Murray, J., and Philippi, E., op. eit., maps 1 and 2, p. 206.

so Murray, J., and Lee, G. V., op. cit., map 2, p. 169.

»l Hanzawa, S., Preliminary report on marine deposits from the southwestern 

North Pacific Ocean, in Records of oceanographic works in Japan, pp. 59-77, Nat. 

Research Council Japan, 1928.

«»Hanzawa, S., op. cit.

«' Trask, P. D., Hammar, H. E., and Wu, C. C., op. cit.
294 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1936
RELATION OF SALINITY TO CALCIUM CARBONATE CONTENT OF MARINE SEDIMENTS 295

Murray and Lee 64 show three lines of equal calcium 

carbonate content—namely, 25, 50, and 75 percent. 

On plate 71 the 50-percent line in the Pacific Ocean is 

based largely on Murray and Lee's 50-percent line, 

but the 10-percent line lies within the limits of Murray 

and Lee's 25-percent line. In general, deposits classified by Murray 65 as red clay contain less than 10 percent of calcium carbonate. He places the upper limit 

at 30 percent and states that the average calcium carbonate content of red clay in the Atlantic Ocean is 

about 8 percent and in the Pacific 5.3 percent.66 Consequently, unless there were data to the contrary, the 

line for 10-percent calchim carbonate on plate 71 is 

placed slightly within the limits for red clay shown by 

Murray and Lee.67 Similarly, in the south Atlantic 

the line for 10 percent is drawn within Pratje's line for 

30 percent. 68

Some parts of the map are based on very little 

information. The Indian Ocean, in latitudes south 

of 50°, and the area off the west coast of France are 

not well represented by samples. Maps of the distribution of bottom deposits by Murray and his 

coworkers were the main guides for these parts of 

plate 71. In the China Sea some deposits may 

contain more than 10 percent of calcium carbonate, 

and in the East Indies and the Mediterranean Sea 

some sediments contain more than 50 percent. The 

calcium carbonate content indicated in the vicinity of 

the islands of the western Pacific should be considered 

only rough estimates.

RESULTS

AREAS IN WHICH RELATIONS ARE DEFINITE

The data presented on plate 71 show that the calcium 

carbonate content of the sediments in many parts of 

the sea is related to surface salinity, surface temperature, 

and depth. The calcium carbonate content, the surface salinity, and the surface temperature in general 

increase from the poles toward the Equator. However, 

in large areas on both sides of the Equator the calcium 

carbonate content is more closely related to the surface 

salinity than to the surface temperature.

In the north Pacific the surface salinity and the 

calcium carbonate content of the sediments are low. 

The area of maximum salinity in the Pacific is in the 

southeastern part, which likewise is characterized by 

deposits rich in calcium carbonate. The western part 

of the south Pacific has a lower surface salinity than 

the eastern part and the sediments contain less calcium 

carbonate in the west than in the east, except for an 

area east of the northern part of Australia, where the 

water in general is less than 2,000 fathoms deep. In

«< Murray, J., and Lee, Q. V., The depth and marine deposits of the Pacific: Harvard Coll. Mus. Comp. Zoology Mem., vol. 38, map 3, p. 169,1909.

65 Murray, J., and Renard, A. F., Challenger Kept., Deep-sea deposits, pp. 192, 

213, 1891. Murray, J., and Hjort, J., The depths of the ocean, p. 166, New York, 

Macmillan Co.. 1912.

«6 Murray, J., and Lee, Q. V., op. cit., p. 20.

M Idem, map 2, p. 169.

" Pratje, O., op. cit., p. 202.

the northern part of the Indian Ocean, the western 

part is more saline than the eastern part, and its 

sediments have a greater content of calcium carbonate. 

The Mediterranean and Red Seas have a high salinity 

and the sediments are rich in calcium carbonate. The 

tongue of high calcium carbonate extending southward 

from Brazil is in an area of high salinity. The salinity 

of the north Atlantic is relatively high even in areas 

where the temperature of the surface water is less than 

20° C., and the sediments in general are rich in calcium 

carbonate. The deposits along the west coast of 

Africa contain considerable calcium carbonate in the 

higher latitudes, but little in the vicinity of the Equator. 

The sediments in the Bay of Panama likewise contain 

little calcium carbonate. In both the Bay of Panama 

and off the west coast of equatorial Africa the surface 

salinity is comparatively low. The surface salinity in 

these areas, therefore, is fairly closely related to the 

calcium carbonate content of the sediments.

The map also shows clearly the influence of depth of 

water on -the calcium carbonate content of the sediments. Almost every area having a depth of more 

than 3,000 fathoms is characterized by deposits 

containing less than 10 percent of calcium carbonate, 

and no area of this depth contains deposits having 

more than 50 percent of calcium carbonate.

AREAS IN WHICH RELATIONS DO NOT SEEM TO HOLJ>

However, though this map indicates that the 

relation of calcium carbonate content of the sediments 

to the surface salinity, surface temperature, and depth 

seems to hold for many areas in the sea, it also shows 

that the relation does not hold for all areas. The 

relation for surface temperature, for example, does 

not apply very well to low latitudes. It is evident 

also that deposits of equal depth differ considerably in 

content of calcium carbonate. In most of the Pacific 

Ocean, except the southeastern part, the sediments 

lying between depths of 2,000 and 3,000 fathoms 

contain little calcium carbonate, whereas in most of 

the Atlantic and in the southeastern Pacific the sediments in that depth interval contain much calcium 

carbonate. The sediments in the northwestern part 

of the Indian Ocean are richer in calcium carbonate 

than the deposits of equal depth in the northeastern 

part. The sediments on the east side of the midAtlantic ridge in general are richer than those lying at 

similar depth on the west side.

The relation for salinity likewise does not apply to 

areas near the mid-Atlantic ridge. The surface 

salinity is greater on the west side than on the east 

side of the ridge in the south Atlantic and equal on the 

two sides in the north Atlantic. Wtist's concept that 

the Antarctic bottom current causes a low content of 

calcium carbonate in the sediments 69 may account for

«• Wiist, Q., Schichtung und Zirkulation des Atlantischen Ozeans: Wiss. Ergeb. 

Deutschen Atlantischen Exped. Meteor, 1925-27, Band 6, Lief. 1, pp. 59-64,1933.
296 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1936

the distribution of calcium carbonate among the 

deposits of the Atlantic Ocean, as he suggests, but it 

does not seem to apply to the Pacific Ocean, where the 

sediments in southern latitudes contain more calcium 

carbonate than those in northern latitudes.

It would also seem that if the surface salinity influenced the deposition of calcium carbonate, the 

sediments underlying the Atlantic equatorial current, 

which is composed of water of relatively low surface 

salinity, should contain comparatively little calcium 

carbonate. The map* does not indicate any such low 

calcium carbonate content in this area. The equatorial current in the Pacific, however, though likewise 

characterized by relatively low surface salinity, is 

underlain by sediments low in calcium carbonate. 

The deposits north of the Pacific equatorial current, 

underlying the area having a salinity of 35 parts per 

thousand, are represented by very few samples, but 

the data available suggest that the sediments are 

slightly richer in calcium carbonate in this area than 

in the vicinity of the equatorial current. However, if 

the calcium carbonate content of the sediments is 

related to the surface salinity, it would seem as if the 

sediments hi the north Pacific in the area underlain 

by water having a salinity of 35 parts per thousand 

should contain more calcium carbonate than they do.

The calcium carbonate content of the deposits off 

southern California and Baja California is about 15 

percent, which is higher than usual for areas having a 

salinity as low as in this region. These sediments are 

fairly rich in bottom-living Foraminifera, which may 

be a contributing cause to the somewhat greater calcium 

carbonate content than would be expected. The sediments off the Mackenzie Delta, in northern Canada, 

contain about 12 percent of calcium carbonate or dolomite. As a considerable proportion of the carbonate 

in these sediments seems to be dolomite,70 it is probable 

that much of the carbonate is derived from particles 

of limestone or dolomite transported from adjacent 

land areas. The sediments of the Black Sea are fairly 

rich in calcium carbonate, but the surface salinity is 

low, being only 18 parts per thousand. '

It would seem, therefore, that the relations of surface 

salinity, surface temperature, and depth to the calcium 

carbonate content, of the sediments are not demonstrated definitely by the areal relations shown on plate 

71. However, as explained above, the deposition of 

calcium carbonate is a very complicated process and 

is affected by a large number of factors, many of which 

operate simultaneously. The individual factors vary 

in their effect in different parts of the ocean. In some 

areas the influence of any particular factor may be 

obscured by the effect of some other factor. A relation 

between the calcium carbonate content of the sediments

70 Trask, P. D., Hammar, H. E., and Wu, C. C., Origin and environment of 

source beds of petroleum, p. 104, Houston, Tex., Gulf Publishing Co., 1932.

and the salinity therefore would not be apparent for all 

areas in the ocean. The surprising feature is that a 

relation is found for so many areas.

COMPARISON WITH RESULTS OF OTHER UttfES OF 

ATTACK

The relation of the areal distribution of calcium 

carbonate content to surface salinity accords fairly 

satisfactorily with the relation indicated by the statistical study of the individual samples. The relation 

indicated by both of these empirical lines of attack 

agrees with the relation indicated by the study of the 

solubility of calcium carbonate in sea water. It seems 

evident, therefore, that the calcium carbonate content 

of the sediments is definitely related to the salinity of 

the water. Areas of high salinity are associated with 

sediments rich in calcium carbonate, and areas of low 

salinity are associated with sediments poor in calcium 

carbonate.

EXPLANATION OF RELATIONSHIPS

The relation of salinity to the calcium carbonate 

content of sediments may be only in part a cause and 

effect relation. The notable increase in calcium carbonate content of sediments as the surface salinity 

rises from 34 to 36 parts per thousand is considerably 

greater than would be indicated by the increase in 

degree of saturation of the water caused by such a rise 

in salinity. The salinity associated with the greatest 

change in calcium carbonate content of the sediments 

is about 35 parts per thousand, which is approximately 

the average salinity of the ocean. It is possible that 

the surface isohalines of 35 parts per thousand may 

roughly mark the line between oversaturation and 

undersaturation of calcium carbonate in the upper 

layers in the sea. That is, areas in which the salinity 

is more than 35 parts per thousand are likely to be 

supersaturated, thus favoring the precipitation of calcium carbonate, and areas in which the salinity is less 

than 35 parts are likely to be undersaturated, thus 

inhibiting the precipitation of calcium carbonate. The 

salinity would thus be only an index of the degree of 

saturation of the water—that is, the relation between 

the salinity and calcium carbonate content of the 

sediments might to a considerable extent be a relation 

that was not one of cause and effect.

Similarly, it is possible that as the salinity rises 

above 35 parts per thousand it affects the activity of 

organisms in a manner not yet known, thus indirectly 

influencing the deposition of calcium carbonate; for, as 

explained above, living organisms, because of their 

effect on the carbon dioxide content of the water, 

constitute one of the most influential factors affecting 

the deposition of calcium carbonate in the sea.

Furthermore, though the salinity in different parts of 

the ocean remains fairly constant from year to year, 

the water in any particular area, in the course of time,
EELATION OF SALINITY TO CALCIUM CARBONATE CONTENT OF MAEINE SEDIMENTS 297

moves to another area in which the salinity is different—that is, the water in the ocean circulates in a more 

or less definite way. The salinity tends to increase in 

certain areas because of evaporation and tends to 

decrease in other areas because of influx of water from 

land or from the sky. The water in areas in which 

evaporation prevails is relatively dense and strives to 

move to areas where the water is less saline and therefore less dense. The sea water, consequently, is constantly but in general very slowly moving hi its effort 

to maintain equilibrium; but because of the effects of 

evaporation and precipitation equilibrium is never 

attained.71 However, a sort of balance is obtained 

which causes the salinity hi different parts of the ocean 

to remain nearly constant, even though the water in 

those areas continues to move.

Consequently, in areas of high salinity, where the 

degree of saturation presumably is greater than 100 

percent, precipitation of calcium carbonate can continue more or less indefinitely, thus favoring the deposition of calcareous sediments. If the water did not 

move, only a comparatively small quantity of calcium 

carbonate could be precipitated, because the degree of 

saturation of the water would soon be lowered to 100 

percent and no more calcium carbonate could be precipitated until the degree of saturation increased again. 

However, because of this slow circulation of the water, 

the physical conditions in any one area remain more or 

less constant, and calcium carbonate can be precipitated 

continually from areas in which the degree of saturation 

of the water is greater than 100 percent. The relation 

of calcium carbonate content of sediments to salinity 

therefore may to a considerable extent be influenced by 

the effect of salinity on oceanic circulation.

The relation of the salinity to the calcium carbonate 

content of sediments may also be due hi part to the 

relation of salinity to time. Experimental data of investigators at the Scripps Institution of Oceanography 

seem to indicate that the precipitation of calcium carbonate from sea water is influenced by the length of 

time the water has remained in a state of supersaturation.72 Salinity is a rough index of the length of time 

water has remained at or near the surface, because the 

basic way in which water becomes saline is through 

evaporation, and the higher the salinity the longer the 

water has been in a position where it could evaporate. 

Therefore if the length of time that the water remains 

in a state of supersaturation is a factor, salinity may be 

an indirect index of the precipitation of calcium 

carbonate.

These possible explanations of the relation of the 

calcium carbonate content of marine sediments to 

salinity are offered as working hypotheses in an attempt

71 Cf. Johnstone, J., An introduction to oceanography, 2d ed., pp. 256-303, 

Liverpool, 1928.

78 Qee, H., Calcium equilibrium in the sea, V, Preliminary experiments on precipitation by removal of carbon dioxide under aseptic conditions: Scripps Inst. Oceanography Tech. ser., vol. 3, no. 7, p. 183, 1932. Jtfoberg, E. Q., Qreenberg, D. M., 

Kevelle, R., and Alien, E. C., The buffer mechanism of sea water: Scripps Inst. 

Oceanography Tech. ser., vol. 3, no. 11. p. 247,252,1934.

to account for the closer relation of the calcium carbonate content of the sediments to the salinity of the 

water than is indicated by the solubility of calcium 

carbonate in sea water.

GEOLOGIC APPLICATION OF RELATIONSHIPS

The sediments the geologist encounters in the field 

leave clues about the conditions under which they 

were deposited. The proper interpretation of these 

clues depends largely upon knowledge of the conditions 

under which sediments now accumulate. As Bigelow 73 

mentions repeatedly, our knowledge of the processes 

and conditions that prevail in the ocean is handicapped 

greatly by paucity of observations. The field is so 

big and the science is so young that many problems 

are far from being solved satisfactorily. The problem 

of deposition, of sediments is no exception to this 

statement. The conditions of deposition of calcium 

carbonate have probably been investigated as fully as 

any other problem of sedimentation, but, as is evident 

from this paper, much is yet to be learned about the 

manner in which calcium carbonate is deposited in 

sediments. Consequently it is hazardous at this 

time to reason backward from the calcium carbonate 

content of ancient sediments and infer the conditions 

under which the sediments were deposited. However, to illustrate the possibilities afforded by studies 

of the calcium carbonate content of ancient sediments, 

two subjects—the deposition of red clay and inferences 

about past climates—may be discussed briefly here.

FORMATION OF RED CLAY

Wattenberg 74 states that below a depth of 500 

meters in the south Atlantic the saturation of the 

water with calcium carbonate ranges between 90 

and 100 percent. The degree of saturation of the 

water in these parts of the ocean is influenced 

strongly by the temperature and by the production of 

carbon dioxide, either by decomposition of organisms 

after death or by the metabolic processes of living 

organisms. The lower temperature and the higher 

carbon dioxide content of the deep water increase the 

solubility of the water for calcium carbonate, with 

the result that the degree of saturation of the water 

becomes less. If the degree of saturation decreases, 

there is a greater tendency for particles of calcium 

carbonate to be dissolved as they fall through the water, 

and the quantity of calcium carbonate deposited in 

the sediments becomes smaller. Conversely, if the 

temperature of the water were increased or if the rate 

of formation of carbon dioxide were lessened, the 

saturation of the water with calcium carbonate would 

be increased and the calcium carbonate content of the 

sediments should become larger.

7> Bigelow, H. B., Oceanography, New York, Houghton Mifflin Co., 1931.

74 Wattenberg, H., Kalziumkarbonat- und Kohlensauregehalt des Meereswassers: 

Wiss. Ergeb. Deutschen Atlantischen Exped. Meteor, 1925-27, Band 8, Teil 2, p. 

222,1933.
298 SHOETEE CONTEIBUTIONS TO GENEEAL GEOLOGY, 1936

According to data presented by Wattenberg 75 for 

temperatures ranging between 0° and 10° C., an increase of 3° would decrease the solubility of calcium 

carbonate in the water about 10 percent—that is, the 

degree of saturation would increase about 10 percent. 

If all the water before the temperature was raised was 

more than 90 percent saturated, which according to 

Wattenberg 76 now holds for the subsurface water of 

the south Atlantic, and presumably for other oceans 

as well, an increase of 10 percent in the degree of saturation vrould cause the water everywhere to be more 

than 100 percent saturated. Particles of calcium 

carbonate therefore would not dissolve as they fell to 

the sea floor, with the result that calcareous sediments 

instead of red clay would be deposited in the ocean. 

Although Wattenberg's data may be subject to correction, they certainly indicate the order of magnitude. 

The absence or scarcity of red clay among ancient 

sediments might therefore be explained by the greater 

degree of saturation of the deep water in the ocean in 

the past than at present. The increase in degree of 

saturation of the water could have been caused by an 

increase in temperature, but it could also have been 

caused by the water remaining at the same temperature long enough to become saturated by solution of 

calcareous particles as they fell to the sea floor, or by 

a decrease in carbon dioxide content of the water.

The cold water that now occupies the lower part of 

the ocean is derived largely from polar regions. It is 

probable that if the polar ice caps were removed the 

water at the bottom of the ocean would become warmer, 

the capacity of the water to hold calcium carbonate in 

solution would become less, and there would be a tendency for the sediments to have a greater content of 

calcium carbonate.

If it is assumed that essentially all the water from 

the surface to the bottom was saturated with calcium 

carbonate at the end of the Pliocene epoch, the advent 

of the ice age would have lowered the temperature of 

most of the ocean, and the degree of saturation of the 

water, particularly of the subsurface layers, would 

have become less. The sediments deposited during 

Pleistocene time in general should therefore contain 

relatively little calcium carbonate.

At the end of the Pleistocene epoch, or perhaps even 

during the warm interglacial intervals, the temperature 

of the ocean would gradually rise and the calcium carbonate content of the sediments accordingly should 

increase. That is, the calcium carbonate content of 

sediments such as Globigerina ooze would diminish 

progressively downward from the surface of the deposits 

until, a zone of pre-Pleistocene (or interglacial) sediments was reached. Such a downward diminution of

'• Wattenberg, H., op. cit., p. 207. 

'«Idem, p. 222.

calcium carbonate is reported by Pratje 77 and Iselin 78 

in Globigerina oozes in the Atlantic. These authors 

regard this downward decrease in carbonate as due to 

progressive upward leaching of the calcium carbonate; 

but the phenomenon is perhaps explained more plausibly by the progressive increase in saturation of the 

overlying water since Pleistocene time.

The same condition would result also if the water 

remained at the same temperature for considerable 

time. If the temperature remained constant for a 

sufficiently long period, the water would eventually 

become saturated, because of solution of calcareous 

particles falling through the water, with the result 

that the calcium carbonate content of the sediments 

would become relatively high. Presumably red clay 

would not be deposited under such conditions until 

the overlying water again became undersaturated with 

calcium carbonate. A general lowering of the temperature of the deeper layers of water seems the simplest 

way to decrease the degree of saturation of the water, 

but increased production of carbon dioxide by any 

cause would have the same effect.

It is evident from this discussion that the depth at 

which red clay now forms in the sea is influenced 

strongly by the degree of undersaturation of the water 

with calcium carbonate, and that in other geologic 

periods the depths at which it could form would probably be different from the present depths.

RELATION OF CALCIUM CARBONATE CONTENT OF ANCIENT 

SEDIMENTS TO CLIMATE

The average salinity of the surface of the ocean is 

about 35 parts per thousand. The sediments in 

regions in which the surface salinity is greater than 

35 parts in general contain considerable calcium carbonate, and the sediments in areas in which the salinity 

is less than 35 parts, particularly in areas in which it 

is less than 34 parts, contain relatively little calcium 

carbonate. (See table 1.) That is, the sediments in 

areas in which the salinity is above the average are 

likely to be rich in calcium t carbonate, and those in 

areas in which the salinity is below the average are 

likely to be poor in calcium carbonate.

This relationship is subject to many exceptions. 

The calcium carbonate content of sediments is influenced by several factors in addition to salinity, 

particularly by the proportion of terrigenous constituents, which in many areas masks the effects of 

other factors; for even though the rate of deposition 

of calcium carbonate is constant, the sediments off 

the mouths of large rivers contain little calcium car-

" Pratje, 0., Geologische Tiefseeforschungen auf der Deutschen Atlantischen 

Expedition: Deutsch. geol. Gesell. Zeitschr., Monatsber., Band 79, p. 203,1927.

78 Iselin, C. O., Recent work on the dynamic oceanography of the North Atlantic: 

Am. Geopbys. Union Trans. 1Mb Ann. Meeting, pp. 88-89, Nat. Research Council, 

1930.
EELATION OF SALINITY TO CALCIUM CAEBONATE CONTENT OF MAEINE SEDIMENTS 299

bonate compared with the sediments off arid coasts. 

Consequently it is not safe to generalize backward 

and infer that if a sediment contains little calcium 

carbonate it necessarily was deposited in water of subnormal salinity, or that if it contains much calcium 

carbonate it was deposited in water having a salinity 

greater than normal. The data presented in this paper 

indicate,-however, that there is a significant chance 

that the calcium carbonate content of some sediments 

reflects the climate, particularly with respect to rainfall, at the time the sediments were deposited.

Therefore, some alternations between limestone and 

calcareous shale or between calcareous shale and noncalcareous shale may represent fluctuations in climate. 

The more calcareous layers might have been deposited

during dry periods, which would favor the evaporation 

of water and tend to increase the salinity in the basin 

of deposition and which at the same time would decrease the quantity of detritus transported to the 

basin of deposition. The less calcareous layers might 

have been deposited during wet periods, in which the 

water had a low salinity and the quantity of, detritus 

transported by rivers was large.

It would be presumptuous to advocate that alternations between limestone and shale should in general 

be interpreted in this way. However, the possibility 

should be mentioned that some alternations between 

limestone and shale or between calcareous and noncalcareous shale might have resulted largely from 

alternate changes in climate.