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STABLE ISOTOPE S~DIES OF WATER EXTRACTED,FROM SPELEOTHEMS

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@CHARLES

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-J. YONGE; B.Sc., M.Phil •..,,

A'Thesis. 1/

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Submitted to the School of Graduate Studies

•·in Partial Fulfilment 9f the Requirements

for the j)egree

Doctor of Philosophy,...

McMaster University

February 1982.'

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•STABLE ISOTOPE STUDIES

OF WATER ...EXTRACTED FROM SPELEOTHEMS

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DOCTOR OF PHILOSOPHY (1982)(Geology)

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,-McMaster University

TITLE:•

Stable Isotope Studies of Water Extractedfrom Spe],eothems "

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AUTHOR:

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Charles J. Yonge, a.sc. (Surrey University,England)', .

M.Phil. (Surrey University,\ England)

• , SUPERVISORS: ' Professor Henry P. Schwarcz' andProfessor Derek C. Ford

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NUMBER OF PAGES: i-xvii; 1-298

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ABSTRACT

Calcite speleothems, if shown to ~~rmed under con-,

ditions of isotopic equilibrium with their 'parent seepage waters,

can be used to determine relative changes i~ the past ,clim~tes

from measurement of, 0 1 'b of the calcite. Furthermore, if 0 1 'b

of the parent seepage water can be estimated and shown to be

equivalent to'meteoric precipitation falling at the cave site,, .

then depositional temperatures can be recovered from the tem-

perature dependent oxygen isotope fractionation of the calcite-

water p~irs. Cave temperature~ generally reflect mean annual

surface temperatures above the cave. Thus, should the deposi-

tional temperature accurately r,ecord the cave temperature, then

analysis of successive growth

vide. a direct measure of past

'layers '. in ,'speleothemsi

temperature change ~t- .

should' pr,o-

a given

. site., .

Estimates of ,0 1 eo tlftpast seepage water can be made, in.

p~inciple, because speleothems incorporate seepage water with-'

in inclusions as they gr.ow. However, since oxygen in the fluid

inclusion water may exchange w~th that in the carbonate phase, '..- '

hydrogen isotopes, which cannot exchange, are measured instead;

&1 80 of the ,original seepage water can then b~ inferred from"

OD, if seepage

wat~r, because

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water can be shown to be equivalent to included

meteor:ic relationships e~ist which li~k them.

•Work prior to this study sl.lgges,ted that,. follo,wing 'the~Od

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outlined above, isotopic temperature~.couldbe re90vered'from

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speleothj'!ms. \The early part of this study involved the construction

and operation of a mass spectromener, and associated extraction

line for aD analyses and'some, modification to existing .appara­

tus for a 1 'b analysis'.

Water samples were then analysed from a number of cave

sites,.mainly in the Eastern U.S., to check the isotopic e~~iv­

alence of seepage water to meteQric precipitation and observe

seasonal 'isotopic variations in seepage and soil water with

r'espect to meteoric precipitation. The. general conclusion. ,reached was that seepage water was equivalent to met~oric pre?

cipitation and that no seasonal variation. occurred in those

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,caves studie~ in detarl. Study of an Antarctic' Ice Core

showed that ~heal 80 _ aD r~lation of meteoric P~ecipi~ation

during the Wisconsin -Glacial 'Maximum: was 'different from' that /'/

at present.

The latter part of this study was concerned with the

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systematics of water extraction and the isotopic.measurement•

of water-calcite pairs from speleothems. A preViously devel-."\

o~ed technique, involving crushing of. the sample in vacuum

,prior t? freezing over the liberated water, was found not.to

be as reproducible as had been stated in the literature, and,~ ,

as a result, an extraction methoa by heating was developed to,

replace it. Although great difficulty was encountered in get-~ , .

ting this technique to function, it was found, eventually, to

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save time in operatio~, to liberate up to 2.4 times more water

and give greater reproducibility than the crushing method.

Attempts to demonstra1:e the isotopic equa'li ty of the two

methods was only partially successful however, but both methods(

seemed to yield water from speleothems that was isotopically, '

depletea with respect to thei~ parent seepage waters.

For-~he la~ter reasori,. experiments were updettaken to

characterize the wa~er within the calcite because of the pos­I

sible presence of structural, isotopically modified water.

pet·rograph<i.c, obse'rvat,ions left no doubt as to the presence of) .. . ~

fluid inclusi~ns from 50~~ down to unresolvable qim~nsions but

it was questionable as to whether or not all the water lay in,I

these\" s~ tes. (IR', polari zed IP and neut~on di ffract~n spectro-

~ scopy of powders in the lOO~ range failed to reveal the pre­

sence of oriented water in ~the calcite lattice although. 'liquid': ~

water'was stiil observed.~, I

, , The isotopic'depleuion 'of calcite-bound water with res-, , ,

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pect to parent'seepage water in modern' samples was found to bei \ •.

~ 22.1: 3.9%. in 60.' This value, when applied to 60 pr?files of

Six 1~~SSil speleotJ~ms to retrieve original seepage water 60,oives

. tId I 1" 1 thatrJ.se 0' ca culate !ca c;te-water pa eotemperatures

are, above zero. ! Comparison of ~hese modified 60 and tempera­

ture brofiles w~t~ other records, such as deep sea and ice coresI •

, ' .suggested, that paleoclimatic :information can be obtained from

isotqpic studies of speleothems. The mechanipm(sl responsible

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for the isotopic fractionation of calcite-bound water as, it is~

incor.porated into the speleothems during growth is speculated

upon as an absorption-like phenomenon but' no firm conclusions•

. are reached.

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ACKNOWLEDGEME~TS

I. would like to thank Drs. Henry Schwarcz and Derek' Ford

fbr their .suggestion of this project, their w1llin~ness to super­

'vise'it and their interest in som~. of the ideas generated from

it thereafter. Further thanks are extended to Henry Schwarcz

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for his critical appraisal of the thesis which resulted in

considerable improvement of the original draft. I also extend

. thanks to Dr. H.G. Thode for his interest ~n the work and

willingness to. sit 'on the supervisory cOIJUTlittee.

I would like to acknowledge the following people who

also helped me during.the research and in the production of the

thesis:

Russell Harmon for helping me to set up the water

sampling programme.

Tom and Cathy Aley for suggesting seepage water ~ollec~

tion sites at the Ozark Underground Laboratory qnd the concien-

tious manner in which'the samples were picked up at regular in-

terv!3ls .

. Mr. 'Proctor and'Mr. Swartz,' proprietors of ,Shenandoah

and Indian Echo Caverns respectively, for their willingness to

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.undertake water sampling programmes on their prope~y.

.', . ,-Bob Bowin~ pnd(Ed Beaver fot innovative.construction of

some of the major electronic components of the D/H mass spectro-

meter and their'friendship outside the professional sphere.'.

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