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Geological Society of America Bulletin

doi: 10.1130/0016-7606(1953)64[1315:RCITS]2.0.CO;2 1953;64;1315-1326Geological Society of America Bulletin

S EPSTEIN, R BUCHSBAUM, H. A LOWENSTAM and H. C UREY SCALEREVISED CARBONATE-WATER ISOTOPIC TEMPERATURE

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BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICAVOL. 64. PP. 1315-1326. 9 FIGS. NOVEMBER 1953

REVISED CARBONATE-WATER ISOTOPIC TEMPERATURE SCALE

BY S. EPSTEIN, JR. BUCHSBACM, H. A. LOWENSTAM, AND H. C. UKEY

ABSTRACTThe relationship between temperature and O18 content relative to that for a Cretaceous belemnite of the

Pee Dee formation previously reported (Epstein, Buchsbaum, Lowenstam, and Urey, 1951) has been re-determined using modified procedures for removing organic matter from shells, and is found to be

t (°O = 16.5 - 4.38 + 0.145*,where 8 is the difference in per mil of the Ols to O16 ratio between the sample and reference gas. The newrelationship agrees with that determined by McCrea (1950) for inorganically precipitated calcium carbonate.Carbonate-carbon dioxide exchange experiments were done to determine the direct and indirect effects oforganic matter in the shell on the mass spectrometer analyses.

CONTENTS

TEXTPage

Introduction 1315Acknowledgements 1315Purification of the calcium carbonate of

marine shells 1316General discussion 1316Purification process 1316Isotope exchange experiments 1317

Temperature scale 1321Discussion and conclusions 1324References cited 1325

ILLUSTRATIONSF gure Page1. Purification apparatus 13172. Furnace for exchange experiments 13183. Surface ocean temperatures at Pacific

Grove, California 13204. Surface ocean temperatures at Santo Tomas 13205. Surface ocean temperatures at point be-

tween Morro and Ensenada 13206. Plot of O18 concentration vs. growth se-

quence of layers in abalone shell 13217. Plot of O18 concentration vs. growth se-

quence of layers in abalone shell 13218. Plot of O18 concentration vs. growth se-

quence of layers in Macoma sp. and inabalone 1321

9. Isotopic temperature scale 1324

INTRODUCTION

Recently the writers (Epstein, Buchsbaum,Lowenstam, and Urey, 1951) reported on thedetermination of a temperature scale formeasuring the temperature at which a marineshell-bearing animal grows its shell by deter-mining the O18/O16 ratio in the calcium carbonateof the shell. Although the method reportedwas fundamentally correct, extraneous oxygenwas introduced into the calcium carbonateduring one of the stages of the processing of theshell which introduced an error in the tempera-ture scale. The complete problem was re-ex-

amined, and a modified method for preparingsamples of carbon dioxide from the calciumcarbonate of the shell is here described.

ACKNOWLEDGMENTS

We are indebted to Dr. Thomas G. Thomp-son, Dr. Emery Swan, and Dr. C. Barnes ofthe Oceanographic Laboratory, University ofWashington, Friday Harbour, Washington, fortheir co-operation in collecting samples. Thefull co-operation of Dr. Rolf Bolin of the Hop-kins Marine Station and Dr. Carl Hubbs ofthe Scripps Institution of Oceanography,

1315



1316 EPSTEIN ET A L.—CARBONATE-WATER ISOTOPIC TEMPERATURE SCALE

La Jolla, California, is gratefully acknowledged.A great deal of the laboratory work was doneby Mrs. Toshiko Mayeda, and her efforts areappreciated.

We wish to express our most sincere thanksto The Geological Society of America, to theAmerican Petroleum Institute, and to theOffice of Naval Research for the grants whichhave made this work possible.

The work for this study was done at theInstitute for Nuclear Studies at The Universityof Chicago.

PURIFICATION OF THE CALCIUM CARBONATEor MARINE SHELLS

General Discussion

The previously described purification of thecalcareous shell consisted of heating 50 mgs ofthe powdered sample in a slow stream of heliumat 470°C. The helium, which was purified fromorganic compounds by passing it over cupricoxide heated to 700°C and through a liquidnitrogen cooled trap, became contaminatedwith oxygen gas originating from the cupricoxide and from back diffusion through thefurnace opening. The oxygen oxidized theorganic material of the powdered shell to formCOz which in turn exchanged with the calciumcarbonate of the shell. Since carbon dioxideformed with atmospheric oxygen analyzesapproximately — 20%0 relative to carbondioxide extracted from calcium carbonate of anormal marine shell, the isotopic exchangelowered the 018/O16 ratio of the oxygen of thecalcium carbonate of the shells. The samplesused for the temperature scale were treated inthe same manner with the result that a nearconstant error was obtained. This approximateduplication masked the detection of the error,resulting in what was thought to be a validtemperature scale. Further work which showeda large discrepancy between the O18/O16

analyses of the calcium carbonate in the pris-matic and pearly layers taken from the samefragment of a shell led to the discovery of theerror. An example of the discrepancies in theanalyses is shown in Table 1.

S= (R .ample / R .ta^rd" 1) 1000

where /?3ampie and Standard are ratios of CO16018

to CO 2 for the sample and standard referencegas respectively, and S is essentially the differ-ence between the O18 content of the sample andthat of the reference gas.

TABLE 1.—O18 ANALYSES FOR COz SAMPLES FROMDIFFERENT LAYERS OF A FRAGMENT FROM

Haliotis Rufescens GROWN AT 21.0°C

Sample

1. Inner pearly layer2.]3.f Intermediate layers*-J5. Outer prismatic layer

s

-3.6,-3.0j-2.0,-1.7,-1.8,

T<ailc°C(old scale)

31.728.o21.820.,21.o

All the analyses in Table 1 are erroneous.The differences in the above results we believeare due to a greater velocity of exchange ofcarbon dioxide with aragonite (pearly layer) asit is converted to calcite during heating. Thisis discussed further.

Purification Process

The process for the destruction of organicmatter in the samples was modified. The ap-paratus is shown in Figure 1. Helium gas flow-ing at a rate of 0.4 cc per second passes througha copper-filled furnace kept at approximately500°C, through an activated charcoal-filledtrap cooled with liquid nitrogen, and into theroasting furnace. The continuous flow of heliumsweeps the volatile decomposition products ofthe heated organic compounds away from thecalcium carbonate and at the same time pro-vides an inert atmosphere over the sample.The sample, in a platinum boat, is inserted intothe furnace while the temperature of the fur-nace is low (less than 200°C) to permit sweepingout of all the air from the furnace before heat-ing of the sample begins. The opening of thefurnace is covered by a cap containing a capil-lary opening to prevent back diffusion of air.Sweeping with helium continues for 20 minutesbefore the heater of the furnace is turned on.This is sufficient to sweep out the furnace aboutsix times. The sample roasts in the furnace atleast 30 minutes after the temperature of the



PURIFICATION OF CALCIUM CARBONATE OF MARINE SHELLS 1317

furnace reaches 470°C. The resulting calciumcarbonate, which is gray, is then reacted withphosphoric acid to release the carbon dioxide

the difference in O^/O1* ratios between thewaters in which the Strombus and the otherspecimens grew is 1.6%0, which is nearly suffi-

TIGHTLY WOUND Cu GAUZEHELIUM

oorok

FIGURE 1.—PURIFICATION APPARATUS

ior mass spectrometric analysis in the mannerdescribed in the previous publication. Underthese conditions of purification the size of thesample, the length of time beyond 30 minutesof heating, and the difference in the type oflayer in the abalone shell do not affect theresults of the analyses, as shown in Table 2.The two fragments grew at different tempera-tures, and hence the analyses should be differ-ent.

The effect of heating by the modified pro-cedure is to decrease the O^/O16 ratio of theoxygen in the resulting calcium carbonate, butto a lesser degree than in the case of heatingin an atmosphere of a mixture of helium andoxygen. The fact that roasting is still necessaryis shown in Table 3.

The data show that heating affects the iso-topic analysis of samples from different animalsdifferently. Although the first three sampleslisted were grown simultaneously in the sametank, their respective mass spectrometer analy-ses check only after the heating procedure hasbeen followed. The analysis for the Strombuschecks those of the other specimen only because

TABLE 2.—EFFECT OF VARYING CONDITIONS OFHEATING ON THE O18 CONTENT OF CaCO3 FROM

Haliotis SAMPLES

Sample

Fragment IPearly layer

Prismatic layerFragment II

Pearly layer

Weightmgs

1050

50

5050

Time ofheatingat470"Cmm.

3030

30

3075

*

— 1.1», — 1.44— 1.32, — 1.29,

-1.00-1.2,

-0.8,-0.86

cient to compensate for the difference in thetemperature at which the specimen grew.

Isotopic Exchange Experiments

Although the heating of the samples in heliumgas with rigorous exclusion of oxygen and otherprecautions outlined have given very consistentresults, the investigation of the cause for the



1318 EPSTEIN ET AL— CARBONATE-WATER 1SOTOPIC TEMPERATURE SCALE

previous errors is important if we are to beconfident that the present consistency in resultsis not due to systematic errors. In the former

TABLE 3.—EFFECTS OF ROASTING ON ANALYSIS OFRATIO OF CaCO3 FROM MARINE

SHELLS

Sample

Snail (Kelletia) . . .Haliotis (prisma-

tic layer)Calcareous wormsSnail (Strombus) . .

GrowthTemp.°C

21.5

21 521.529.5

Freshunheatedsample<S

-0.33

-0 96-0.46-1.3

Sampleheatedin He gas

-1.4,

-1.5,-1.3,-1.46

Changedue toheating

-l.lo

-0.56-0.90-0.16

produced from the decomposition of shell or-ganic matter may exchange with the carbonate.

These possibilities could be investigated ifthe oxygen in the organic matter could belabeled and its contribution to the carbondioxide extracted from the powdered shelldetected. It was hoped that the oxygen in theorganic matter could be preferentially enrichedin O18 relative to the CaCOs of the shell (andthus labeled) by heating the powder in anatmosphere of carbon dioxide enriched inO18 at temperatures high enough to facilitateexchange but low enough so that all the organicmatter is not driven from the powder. Suchpreferential O18 enrichment of the organicmaterial should be detected by comparing the

STOPCOCKTO VACUUM

SYSTEM MANIFOLD

FIGTJRE 2.—FURNACE FOR EXCHANGE EXPERIMENTS

paper, it was concluded that the reaction ofshells containing organic matter with phos-phoric acid does not produce an impurity ofmasses 44 and 46 which interferes with themass spectrometric analyses, and we know ofno reason to change this view.

However, organic matter may affect the O18

content of the carbon dioxide extracted fromshell in the following ways: (1) Its reactionwith phosphoric acid may produce carbondioxide different in isotopic composition fromthat produced from calcium carbonate of theshell; (2) Even in the absence of oxygen duringthe heating of shell sample in helium at 470°C,carbon dioxide or other oxygen compounds

mass spectrometer analyses for carbon dioxidesamples extracted from the above powder withthat extracted from powder which has beensubjected to the above exchange after its or-ganic matter is removed by heating at 470°Cin an atmosphere of helium. The procedureused for these exchange experiments is describedbelow.

A fragment of shell from a Strombus gigaswhich was 100 per cent aragonite and a frag-ment from an oyster shell were separatelypowdered, and a 30-milligram aliquot fromeach powder sample heated in a helium gasstream by the method described in the purifica-tion procedure. This procedure converted thearagonite to calcite in the former case and



PURIFICATION OF CALCIUM CARBONATE OF MARINE SHELLS 1319

destroyed the organic matter in both cases.Thirty milligrams, which will be designated asSample I of the original unheated aragonitepowdered shell, and an equal amount of theheated powder, designated as Sample II, were

ment in O18 was 0.42. Thus organic matter mustdirectly or indirectly affect the isotopic compo-sition of the carbon dioxide extracted from theshell. Since for Sample III the enrichment dueto exchange at 320°C [comparison between

TABLE 4.—POWDERED SHEix-COz EXCHANGETemp, of heating°C

Not heated320320420

Not heated320375

Time of heatingMins.

306060

6060

Sample I (Crystal form after exchange)8°/M

(a) +0 . 1, (100% aragonite)(b) +1 .30 (100% aragonite)(c) +1 .98 (100% aragonite)(d) +14.55(80%calcite)

Sample III Calcite(a) -2.02(b) -0.38(c) +1.94

Sample II Calcite«Vw

(a) -0.2,(b) +0.05(c) +0.2,(d) +0.7,

Sample IV Calcite(a) -2.3,(b) -1.58

placed simultaneously in separate boats in afurnace shown in Figure 2. The system wasthoroughly evacuated, after which 85 cc ofcarbon dioxide which analyzed +100%0higher in Ols relative to our standard wasintroduced into the furnace. The resultingpressure in the furnace was approximately halfan atmosphere. The temperature of the furnacewas raised to the desired value, and the samplesallowed to exchange with the carbon dioxidefor the desired length of time. The O18 enrichedcarbon dioxide was then removed, and 15milligrams of each sample was reacted withphosphoric acid as previously described. Thesame procedure was repeated using the pow-dered oyster shell with the untreated sampledesignated as Sample III and the helium heatedsample as Sample IV. The mass spectrometricanalyses of the gas samples are given in Table 4.The crystalline form of the calcium carbonateswas determined by x-ray analyses.

Comparison of the difference in analysesbetween Sample I(a) and Sample I(c) withthe difference in analysis between SampleII (a) and Sample II (c) shows that in the caseof Sample I, which contained organic matter,exchange with O18 enriched carbon dioxideresulted in an enrichment of the O18 of thecarbon dioxide extracted from the shell of1.7 9 while in the case of Sample II, from whichorganic matter was first removed before ex-change with O18 enriched carbon dioxide waspermitted to proceed, the resultant enrich-

TABLE 5.—EFFECT OF HEATING AT 475°C INHELIUM ON O18 EXCHANGED SAMPLES

Sample(Exchange temp)

I(c) (320°C)III(b) (320°C)III(c) (375°C)IV(b) (375°C)

Before,heating inHelium(fromTable 4)S

1.98-0.38

1.94-1.58

AfterheatinginHeliumS

1.20-1.09

l.ls-1.9,

Changein O18contenta

-0.78-0.71-0.76-0.33

III(a) and III(b)] is 1.64 and is similar to thatfor Sample I it appears that in this case arago-nite and calcite powders behave similarly toexchange with carbon dioxide. The analyses forSample I(d) show a very marked increase inO18 when aragonite transformed to calcite,whereas such an increase did not occur for theSample II(d) which was treated similarly.Although further work is necessary to under-stand this effect, it is very likely that suchtransformation should weaken the bonds inthe calcium carbonate and lower the activationenergy necessary for exchange between calciumcarbonate and carbon dioxide. This increase inexchange rate agrees with the results of Table 1—namely, the aragonite pearly layer of anabalone shell was more markedly affected bysurrounding carbon dioxide than was the cal-cite prismatic layer when both were heated at470°C.



1320 EPSTEIN ET AL.—CARBONATE-WATER ISOTOPIC TEMPERATURE SCALE

If the powdered samples of shell which werenot first heated at 470°C and which were sub-jected to exchange with O18 enriched carbon

I I I I I I I I I I I I I4 6 8

MONTHS10 12

FIGURE 3.—SURFACE OCEAN TEMPERATURES ATPACIFIC GROVE, CALIFORNIA

Average maximum 14.5°C, Average minimum

bon dioxide extracted from such heated samples.Accordingly, aliquots from Samples I(c), III(b),III(c), and IV(b) were heated at 470°C, and thecarbon dioxide from these samples analyzed.The results are shown in Table 5.

Table 5 shows that the first three sampleslisted have lost O18 to a greater extent than didthe last sample during the heating at 475°C.The first three samples contained organic mat-ter while exchanging with O18 enriched carbondioxide, while the last sample was purified oforganic matter before it was allowed to ex-change. It seems, then, that heating at 470°Cin an atmosphere of helium eliminates someorganic matter which would otherwise affectthe analyses of the carbon dioxide extractedfrom a powdered shell. That no exchange hastaken place during this 470°C heating is shownby the fact that Samples I(c) and III(b) have

0°

inr I i i i I i i I i I I i I I I I I8 1 4 8 1 2

MONTHFIGURE 4.—SURFACE OCEAN TEMPERATURES AT SANTO TOMAS

Average maximum 17°C, Average minimum 12"C.

20

15

I I I I I I I I I I I I I I I8 I 5 10

MONTHFIGURE 5.—SURFACE OCEAN TEMPERATURES AT POINT BETWEEN MORRO AND ENSENADA

Average maximum 21°C, Average minimum 15°C.

dioxide contain preferentially O18 enrichedorganic compounds, then further heating ofthese samples in an atmosphere of helium at470°C should destroy the organic matter, result-ing in a lowering of the O18 content of the car-

been reduced in O18 by the same amount. Sincethe former sample was aragonite which con-verted to calcite at 470°C and the latter samplewas originally calcite and thus suffered nocrystallographic transformation during the



TEMPERATURE SCALE 1321

0

0.4

0.8

1.2

1.6

I

n'- "̂-i;V

' L. ,.-J

H

^ 7

V1 1 1

(CORR)

O.I 0.2 0.3 0 O.I 0.2 0.3SUM OF WEIGHTS OF SAMPLES (gs)

FIGURE 6.—PLOT OF O18 CONCENTRATION vs.GROWTH SEQUENCE OF LAYERS IN ABALONE

SHELL(Baliotis, Pacific Grove, Temperature 11-14.5°C)

0

0.4

0.8

(CORR) '-Z1.6

V f XV -̂V-'~ ^_

I

,-i•s.r-" --

n

O.I 0.20.30.40.5 0 O.I 0.20.3SUM OF WEIGHTS OF SAMPLES (gs)

FIGURE 7.—PLOT OF O18 CONCENTRATION vs.GROWTH SEQUENCE or LAYERS IN ABALONE

SHELL(Haliotis, St. Tomas, Temperature 12-17°C)

enrichments are particularly large in the caseof the sample that had organic matter duringthe exchange experiments. That calcium carbon-ate should exchange more readily when in-timately mixed with decomposing organicmatter is not surprising in the light of the workof Armstrong and Schubert (1947). They foundthat presence of water increases the rate ofexchange between CO2 and carbonate. Pos-sibly the less marked exchange that occurredin the case of the shell powder which had beenpreviously purified of organic matter is due towater from its neighboring unpurified samplewhich had contaminated carbon dioxide in thefurnace, and that the apparent loss of O18 bySample IV(b) after being heated in heliumat 470°C is due to loss of organic matter pickedup by this sample from its neighboring SampleIII(b) during the exchange experiment.

It has been noted that finely powdered Fora-minifera which have been exposed to air for afew months will in some cases show a lowerO18 content relative to that of freshly powderedshell. Fortunately this effect does not seem toexist for the samples used in the determinationof the temperature scale since some of the

1.2-1.6-

2.0-

-1.2--0.6-"-0.4.

'-^ '̂'' 0.0-0.4.

t i i

_*

^™ __ /

'"̂, ,

(CORR)

O.I 0.2 0.3 0 O.I 0.2SUM OF WEIGHTS OF SAMPLES (gs)

FIGURE 8.—PLOT OF O" CONCENTRATION vs. GROWTH SEQUENCE OF LAYERS IN Macoma sp. (at left;Middle Channel, Temperature 7-9°C) AND IN ABALONE (at right, Haliotis; Point between Morro and

Ensenada points, Temperature 15-21°C)

heating, then if exchange had taken place dur-ing the heating Sample I(c) would have beenless depleted in O18 than Sample III(b).

The results in Column 3, when comparedwith the O18 analyses for the samples of oysterand Strombus which have merely been heatedin helium at 470°C (IV(a) and II(a) re-spectively) show that there is a resultant en-richment in O18 in the calcium carbonate thatoccurred during the exchange experiment. The

results reported here have been obtained over aperiod of a year. This effect should be guardedagainst in any further work on freshly gatheredsea shells.

TEMPERATURE SCALEWith the development of a reliable process

for destroying organic matter in organicallyprecipitated calcium carbonate the work on thetemperature scale was continued.



1322 EPSTEIN ET AL— CARBONATE-WATER ISOTOPIC TEMPERATURE SCALE

TABLE 6.—DESCRIPTION OF SHELL SAMPLE USED FOR DETERMINATION OF TEMPERATURESCALE

Location

Thermostated tank atHopkins Marine Sta-tion, Pacific Grove,Calif.

Thermostated tank atScripps Institution ofOceanography, LaJolla, Calif.

Bermuda, tank in lab-oratory

Hopkins Marine Sta-tion

Specimen

1. Black abalone, Halio-tis cracherodii






7. Black abalone, Halio-lis cracherodii


9 (a). Black abalone, Hali-otis cracherodii

(b). Black abalone, Hali-otis cracherodii






13 (a). Black abalone, Uali-otis cracherodii


14. Snail Kellatia kdlettii

15. Oyster Mytelles cali-fornianus

16. Calcareous worm

17. S trombus gigas

18. Haliotis cracherodii

Part of specimen used

Regenerated edge(mother of pearl)

Regenerated holes of spec.1 + spec. 2 (mother ofpearl)

Regenerated hole(mother of pearl)

Regenerated notch inedge of shell

Regenerated notch

Regenerated notch

Regenerated notch

Regenerated hole

Pearly layer of regener-ated notch

Prismatic layer of regen-erated notch


Prismatic layer of thesame



Average of regeneratednotch



Average sample of regen-erated edge

Average sample of regen-erated edge

Average sample

Regenerated edge

Fragment used in sea-sonal variation

Temp. °C

19

21.5

29.5

Min. 11Max. 14.5

WaterAnalysis

-0.44

-0.45

+1.13

-0.44



TEMPERATURE SCALE

TABLE 6—Continued

1323

Location

Santo Tomas

Point between Morroand Ensenada Points

Middle Channel, PugetSound

Specimen

19. Haliotis cracherodii

20. Haliotis rufescens

21. Macoma sp.

Part of specimen used




Temp. "C.

Min. 12Max. 17

Min. ISMax. 21

Min. 7.2Max. 9.5

WaterAnalysisQ13

-0.43

-0.29

-0.63

To establish the relationship between O18/016

ratio of the oxygen in calcium carbonate pre-cipitated by marine shells and the temperatureat which they were precipitated, regeneratedfragments of shell grown in temperature-controlled tanks as well as shells collected intheir natural surroundings were used. Onegroup of animals whose shells were notched ordrilled and which then repaired their shells ina thermostated tank at 19°C was sent to usby Dr. Rolf Bolin from the Hopkins MarineLaboratory. A Strombus gigas which regeneratedpart of its shell at 29.5°C in a tank at Ber-muda provided shell for a high-temperaturecalibration point. A third group of animalswhich regenerated their notched and drilledshells at 21.5°C was sent to us by Dr. CarlHubbs. These three groups then provided threecalibration points.

The other points on the curve were obtainedby determining the variation of O18/O16 ratio incalcium carbonate samples ground off fromsuccessive growth layers from a rectangularpiece of shell. The marine shells grew in a loca-tion whose seasonal variation of temperatureis known. The locations chosen were off theshores of Santo Tomas, a point between Morroand Ensenada points on the west coast ofLower California, and at Pacific Grove, Cali-fornia, and from Middle Channel in FridayHarbour, Puget Sound, Washington. The sea-sonal temperature variation of the first threelocations is shown in Figures 3, 4, and 5. Thedata for the first two localities mentioned weresent to us by Dr. Carl L. Hubbs, and the datafor the curve in Figure 5 are from Skagsbergand Phelps (1946). The samples from Middle

TABLE 7.—ISOTOPIC ANALYSES OF ORGANIC CAL-CIUM CARBONATE SAMPLES

Spec.No.(Table6)

12345678

9(a)(b)

10(a)(b)

11 (a)

(b)1213(a)

(b)14(a)

(b)

151617(a)

(b)

6 fobs.)

-1.03-1.28-1.20-1.06-1.06-1.38, -1.10-1.12, -0.88-2.23, -1.80,

-2.23-1.50, -1.50-1.63, -1.30,

-1.64,-1.52,-1.39

-1.57, -1.64-1.22, -1.43-1.46, -1.64,

-1.64-1.12-1.52-1.70, -1.78,

-1.86,-1.60

-1.42, -1.50-1.48, -1.43,

-1.27-1.53, -1.45,

-1.62-1.44, -1.52-1.29, -1.42-1.41, -1.40,

-1.50-1.51

sAverage

-1.03-1.28-1.20-1.06-1.06-1.24-1.00-2.09

-1.50

-1.47

-1.44

-1.52-1.64

-1.46

-1.48-1.36-1.46

iAveragecorrected

-0.59-0.84-0.76-0.62-0.62-0.80-0.56-1.65

-1.05

-1.02

-0.99

-1.07-1.19

-1.01

-1.03-0.91-2.59

Temp.°C

1919191919191921.5

21.5

21.5

21.5

21.521.5

21.5

21.521.529.5



1324 EPSTEIN ET AL — CARBONATE-WATER ISOTOPIC TEMPERATURE SCALE

TABLE 7—Continued

30

20

-2 0S %.

Spec.No.(Table6)

18(a)(b)

19(a)(b)

20(a)(b)

21(a)(b)

S fobs.) ,Average

1.020.060.58

-0.350.03

-1.201.641.20

sAveragecorrected

1.460.501.010.080.32

-0.912.271.83

Temp.°C

1114.512171521

79

FIGURE 9.—ISOTOPIC TEMPERATURE SCALE

Channel locality lived at a depth of 145 meters,and the temperature ranges from about 9°Cduring July to about 7°C during December.The average maxima and minima of the tem-peratures of the localities were then estimatedand matched with the maxima and minima inthe respective curves resulting from the plotagainst the succession of layers in the shellsshown in Figures 6, 7, and 8.

Table 6 lists the species and their locationand temperatures of shell growth. The isotopiccomposition of the water in which these formsgrew has been more carefully redetermined inconjunction with a complete program of deter-mining the variation of isotopic composition

waters. From this study which will be reportedelsewhere the analysis for the Ou/016 ratio ofcarbon dioxide equilibrated with the averagemarine water was found to be 0.0%0 relativeto our working standard gas. Therefore thecorrection, due to differences of O^/O16 ofwater in which the marine animals grow, ofthe isotopic analysis of CaC03 from the averageisotopic composition of the oceans will be thenegative value of the analyses for the watermade in the same manner and is listed in thelast column of Table 6. In Table 7 are listedthe specimen numbers as specified in Table 6,the S analyses, and the 5 analyses correctedfor the isotopic composition of the water. Fig-ure 9 shows a plot of the results of the lasttwo columns of Table 7.

Least squares calculations of the data inTable 7 gave the following equation:

/ = 16.5 - 4.35 + 0.1462,

where t is the temperature in °C, d is the permildifferences between the ratio of masses 46 and44 of the sample and of the working gas. Theintercept 16.5 is characteristic of the standardand the choice of the isotopic composition ofthe average marine waters. The standard devia-tion for / is equal to ±0.6°C.

DISCUSSION AND CONCLUSIONS

There is one experimental point on the curvewhich deviates far beyond the experimentalerror from the calculated curve. This point wasdetermined using mother of pearl shell whichwas regenerated at 21.5°C by the abalone inthe process of covering a hole drilled in theshell. Similar points at 19°C deviate in thesame direction, to a much lesser degree. Pos-sibly such calcium carbonate may have beenlaid down by the abalone with sufficient rapidityto prevent complete isotopic equilibration be-tween the solid calcium carbonate and sur-rounding water.

Least-squares calculations of data deter-mined by McCrea (1950) for inorganicallyprecipitated calcium carbonate in the range of7-25°C give slopes of 5.2 and 4.1 and interceptsof 17.5 and 13.0 for series using Florida and



REFERENCES CITED 1325

Cape Cod waters respectively. The value ofthe slopes is essentially in agreement withthe present value of 4.3. Florida water ofsalinity 36.5 collected at Jacksonville analyzes+0.7%0, while the standard used by McCreaanalyzes +0.4%0 relative to our present work-ing standard. The intercept obtained byMcCrea where he used Florida water, whencorrected for the differences in the S of thewater and standards, becomes 16.0. The closeagreement between the temperature scalesbased on inorganic and organic precipitationleads us to conclude that a valid isotopictemperature scale is here reported. The secondequation from McCrea's data cannot be cor-rected since we do not have a sample of thewater which he used.

REFERENCES CITEDARMSTRONG, W. D., AND SCHUBERT, J., 1947, Ex-

change of carbon dioxide between bariumcarbonate and the atmosphere: Science, v.106, p. 403.

EPSTEIN, S., BUCHSBAUM, R., LOWENSTAM, H.,AND UREY, H. C., 1951, Carbonate-water iso-topic temperature scale: Geol. Soc. AmericaBull., v. 62, p. 417-426.

McCREA, J. M., 1950, On the isotopic chemistryof carbonates and a paleotemperature scale:Jour. Chem. Physics, v. 18, p. 849-857.

SKAGSBERG, T., AND PHELPS, A., 1946, Hydrog-raphy of Monterey Bay, California, Thermalconditons Part II (1934-1950): Am. Philos.Soc., Proc., v. 90, p. 350-386.

CALIFORNIA INSTITUTE or TECHNOLOGY, PASADENA,CALIF.; UNIVERSITY or PITTSBURGH, PITTSBURGH,PA.; CALIFORNIA INSTITUTE or TECHNOLOGY,PASADENA, CALIF.; INSTITUTE FOR NUCLEARSTUDIES, UNIVERSITY OF CHICAGO, CHICAGO, ILL.

MANUSCRIPT RECEIVED BY THE SECRETARY OFTHE SOCIETY, DECEMBER 10, 1952

PROJECT GRANT 517/47/S48



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