.: ,~-

dety, aims to gather togethere. The original series of

e and illustrate the commonling the reader to identifybeen enlarged to include

emes.s usefulness to the practisingof the gaps in this knowledge,lion.

tlIogy, University of Exeter

. D. BRASIER, Lecturer in

.. Department of Geology,ord

••. Department of Geology,

icoIogical Studies, Plymouth

.. MURRA Y, Professor of

also more advanced worksimportant books recently

E.E.HUMPHRIES

of the State Museum for

Ph=ing. Wye College

CONODONTS:Investigative Techniques

and Applications

Editor:RONALD L. AUSTIN, B.Sc.,Ph.D.

Senior LecturerUniversity of Southampton

~Published by

ELLIS HORWOOD LIMITEDPublishers· Chichester

forTHE BRITISH MICROPALAEONTOLOGICAL SOCIETY

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pter 1I

tee 1 Reo

© 1987 The British Micropalaeontological Society/Ellis Horwood Limited

British Library Cataloguing in Publication DataConodonts: investigative techniques and applications. -(British Micropalaeontological Society series)1. Conodonts1. Austin, R. L. 11.Series562'.2 QE899Library of Congress Card No. 86-20061ISBN 0-85312-907-X (Ellis Horwood Limited)ISBN 0-470-20697-7 (Halsted Press)Phototypeset in Times by Ellis Horwood LimitedPrinted in Great Britain by Butler & Tanner, Frome,Somerset

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14The electron spin resonance technique in conodontstudiesZ. Belka, K. Miaskiewicz and T. Zydorowicz

Conodonts from Ordovician to Triassic agedeposits have been investigated by electron spinresonance. This technique permits detection ofthe type and relative number of paramagneticcentres having different absorption signals.Conodonts exhibit signals induced by naturalbackground radiation. The intensity of thesignals is dependent upon the radiation dosereceived by the sample as well as upon thetemperature.

Electron spin resonance is not recom-mended for dating the age of conodonts but canbe used for determining the age of completionof the latest heating event (i.e. most frequentlythe time ofthe last upheaval of the host-rocks).Because there is a correlation between the con-odont colour alteration index (CAI) and theelectron spin resonance spectral structure, itseems that this method may be applied to test-ing CAI values.

14.1 INTRODUCTION

Electron spin resonance (ESR) (or electronparamagnetic resonance) is a branch of spec-troscopy in which microwave-frequency radia-tion is absorbed by molecules, ions or atomspossessing unpaired electrons. This technique

enables detection of the presence and relativeabundance of various paramagnetic centres.These centres include radicals, vacant latticepoints and transition metals.

ESR spectroscopy utilizes the differentenergy states which arise from the interaction ofthe magnetic moment of an unpaired electronwith a static magnetic field, and the transitionbetween them upon the application of micro-wave radiation.

The basic equation is

hv = g~BB

where v is the fixed frequency of the microwaveradiation, B is the strength of the static magne-tic field at resonance, ~B is the electron Bohrmagneton, and g is the Lande factor, which is aunique property of the electron as a whole. Ifthe electron spin is the only source of the mag-netism, then g = 2.0023. In atoms or ions anorbital angular momentum may be also present,in which case g is different from the free spinvalue. The g factor is measured from thespectra by the use of standards (commonlydiphenylpicrylhydrazyl, with g = 2.0036) andthe relationship

Bg _ g standard- standard B

Sec. 14.1]

(

When nuclei wiare present in paelectron magneticnuclear magneticsplits the ESR signhyperfine splitting).ting is described bystant A which is Ispectra by the sejpeaks in terms of m(mT) or gauss (G»monly presented aderivative of the j

against the magne .

A

~

(a)

dA--( dB

~

(b)L-- _

r Fig. 14.1 - Tspectrum presei

and (l

The g factor and hare generally anisvalues along threesecond-rank tens

Sec. 14.1] Introduction 231

conodont

When nuclei with spin value I not equal to 0are present in paramagnetic molecules, theelectron magnetic moment can interact withnuclear magnetic moments. This interactionsplits the ESR signal on some lines (so-calledhyperfine splitting). The magnitude of the split-ting is described by the hyperfine splitting con-stant A which is measured directly from thespectra by the separation of the componentpeaks in terms of magnetic field units (millitesla(mT) or gauss (G)). The ESR spectra are com-monly presented as derivatives, e.g. the firstderivative of the absorption curve is plottedagainst the magnetic field strength B (Fig. 14.1).

rresence and relativearamagnetic centres.meals, vacant lattice

A

tilizes the differentrom the interaction ofan unpaired electron. and the transition

application of micro-lalL- _

l

dAdB

y of the microwaveof the static magne-. the electron Bohrde factor, which is a

on as a whole. Ifuy source of the mag-In atoms or ions an

n may be also present,r from the free spinmeasured from the

dards (commonlyrith g = 2.0036) and

IblL-------~-------r.:~

Fig. 14.1 -- The shape of a typical ESRspectrum presented as (a) absorption curve

and (b) derivative curve.

The g factor and hyperfine coupling constant Aare generally anisotropic, with three principalvalues along three orthogonal axes (i.e. they aresecond-rank tensors). In gaseous and liquid

B

samples the anisotropy is averaged, but in solidsamples the anisotropy significantly alters theshape of the ESR spectrum.

Comprehensive reviews of ESR spectros-copy have been published by Atherton (1973),Drago (1977) and Symons (1978). ESR spec-troscopy has occasionally been applied to geolo-gical materials. Ikeya and Miki (1980) reportedthat only a few geological materials are suitablefor dating by ESR, provided that the materialspossess defects and traps of high thermal stabi-lity, e.g. apatites. ESR spectroscopy has beenused to date stalactites (Ikeya, 1975), animaland human bones (Ikeya and Miki, 1980), andflints (Robins et al., 1978; Garrison et al.,1981). As a dating technique, it has beenapplied to conodonts by Morency et al. (1970).In addition, ESR spectroscopy has been used toderive information on the formation of manga-nese nodules (Wakeham and Carpenter, 1974)and the distribution of Mn2+ in carbonates(Schindler and Ghose, 1970; Wildeman, 1970;Low and Zeira, 1972). Cubbitt and Wilkinson(1976) used ESR spectroscopy to classify Kan-sas shales, and Gilinskaya et al. (1982) haveclassified Siberian apatites. The potential ofESR spectroscopy in studies of clay mineralshas been discussed by Friedlander et al. (1963).

Conodonts consist of carbonate apatite,approximately of the composition of themineral francolite (Pietzner et al., 1968). Inaddition to the mineral phase, conodonts con-tain an organic soft tissue characterized by cells,fibrous material and lumina (cf. Fahraeus andFahraeus-van Ree, 1985). It is assumed thatparamagnetic centres in conodonts can berelated to both the inorganic and the organicmaterials. When the paramagnetic centres con-sist of organic free radicals and/or electrontraps, the relative number of the centres isdependent upon external factors, such as thetotal radiation or temperature.

The purpose of this study is to determine thedependence of the presence and intensity ofconodont ESR signals upon sample age in addi-tion to temperature and the micromorphologi-cal composition. Since heat alters conodont

B

232 The electron spin resonance technique in conodont studies [Ch. 14 Sec. 14.4]

Table 14.1- Conodont samples used in this study.

Sample Locality Age Conodont CAI A1 Erratic boulder from Poland Arenig 1 J_2 Mojcza, Holy Cross Mountains, Poland Llanvirn 13 Borehole Solarnia IG-1, depth of 845m,

Silesia, Poland Givetian 4 ""I

4 Amsdell Creek, New York, USA Frasnian 35 Borehole ZMZ-23, depth of 281m, Cracow

Upland, Poland Frasnian 3.56 Harz Mountains, Germany Famennian 47 Plucki, Holy Cross Mountains, Poland Frasnian 28 Dule, Holy Cross Mountains, Poland Famennian 29 Borehole BK-318, depth of 662m, Cracow

Upland, Poland Famennian 2.5~10 Borehole B-1, depth of 940m, Cracow

Upland, Poland Tournaisian 2 OP11 Galezice, Holy Cross Mountains, Poland Visean 2 t12 Lower Silesia, Poland Ladinian 113 Strzelce Opolskie, Lower Silesia, Poland Anisian 114 Strzelce Opolskie, Lower Silesia, Poland Anisian 115 Strzelce Opolskie, Lower Silesia, Poland Anisian 116 Gasiorowice, Lower Silesia, Poland Anisian 1 Fig. 14.2 - ESR17 Botneheia, Isfjorden, Svalbard Ladinian 2 recognized signals

colour (Epstein et al., 1977) and other investi-gations (cf. Hutton and Troup, 1966) haveshown that the colour of many materials isrelated to paramagnetic centres, we have alsocompared the conodont ESR spectra with theircolour alteration index (CAI) values.

The study was performed on 17 conodontsamples (see Table 14.1) which range in agefrom Ordovician to Triassic and were obtainedfrom various localities in Poland, North Amer-ica, Germany and Svalbard. The results pre-sented are preliminary and indicate only quali-tative analyses of the spectra.

14.2 EXPERIMENTAL CONDITIONSThe conodont preparation was identical withthat for strati graphic work. The minimumrecommended weight of the conodont sample is

5mg, i.e. about 300 conodont elements of vari-ous growth stages.

The ESR spectra were recorded on an SE/X2542 spectrometer (Radiopan, Poland), usingthe X band with 100kHz modulation. All spec-tra were recorded using the same modulationamplitude (0.1 mT) and microwave energy.This procedure does not damage the conodontmaterial.

14.2). The splitting i:fine splitting con la

intensity ratio of 1:The structure of

between samples. wlwas always identicalmarked g factor anis

14.4 SOURCES OF

14.3 SPECTRAL STRUCTUREFour distinct signals can usually be observed inthe ESR spectra of conodonts (Fig. 14.2). Thesignals have been labelled A, B, C and D inorder of descending g factor values (Table14.2). In addition, some spectra indicate hyper-fine splitting, with a peak split into four compo-nent peaks (indicated by asterisks (*) in Fig.

Our preliminaryallowed identificarionetic centres withincan only indicatetherefore the signalquestion.

--~-

es [Ch. 14

lont elements of vari-

recorded on an SE/Xopan, Poland), usingnodulation. All spec-:he same modulationmicrowave energy.

lamage the conodont

TUREually be observed inonts (Fig. 14.2). Thed A, B, C and D infactor values (TableJectra indicate hyper-split into four compo-asterisks (*) in Fig.

Conodont CAI

11

43

3.5422

2.5

22111112

Sec. 14.4] Sources of signals 233

14.2). The splitting is characterized by a hyper-fine splitting constant A of 2.31mT, and anintensity ratio of 1:3:3:l.

The structure of signals B, C and D variedbetween samples, whereas signal A, if present,was always identical in shape and showed a verymarked g factor anisotropy.

l

14.4 SOURCES OF SIGNALSOur preliminary investigations have notallowed identification of the specific paramag-netic centres within the conodonts. The datacan only indicate possible signal sources, andtherefore the signal source remains an openquestion.

Peak asymmetry, as shown by signal A, isrelated to the mineral content of the conodont.

Signals with g factors very similar to those ofpeaks Band C were noted in the spectraobtained from the apatites from various meta-morphic rocks of Siberia (Gilinskaya et al.,1982). The signals were reported to have beenproduced by the radicals SO; and PO~-.Therefore, signal B is probably derived fromthe SO; radical, the signal of which has acongruent g factor. PO~- radicals originatefrom damage of the apatite structure whenuranium ions replace calcium ions (Gilinskayaand Shcherbakova, 1975; Gilinskaya et al.,1982), the concentration of the radicals being

/'

!/c

t ~

~ ~o 11 vD,V \f 11\

0

~\

I B

, 1 ~ ()

t \ IDPPH1mT

t'---J

Fig. 14.2 - ESR spectrum obtained for conodonts of the Amsdell Creek locality (sample 4), to show therecognized signals A, B, C and D present in the ESR spectra of conodonts: *, an additional signal split on four

component peaks; DPPH, diphenylpicrylhydrazyl.

234 The electron spin resonance technique in conodont studies

Table 14.2 - g Factor values of signals presentin conodont ESR spectra.

Signal g factor

ABCD

2.051±0.00l2.004±0.OOl2.000±0.0011.999±0.001

proportional to the uranium content. It is unlik-ely that signal C could originate from PO~-radicals, because uranium was not detected inthe conodont crowns, and the presence of ura-nium in the conodont bases is doubtful(Pietzner et al., 1968).

We attribute signal D, the only centre whichis stable to 1000°C (cf. table 14.3), to thepresence of organic matter.

A signal split into four component peaks(see Fig. 14.2) indicated the presence of threeequivalent nuclei with a spin value I of !, thenucleus 19Fbeing a probable source.

14.5 SIGNAL INTENSITY AS A FUNCTIONOF TIME AND TEMPERATURE

Geological dating by ESR spectroscopy is basedon the general principle that the signals emittedby certain geological materials (bones, flints,apatites, etc.) are proportional to the totalradiation received. By assuming a constantradiation dose, the signals are therefore pro-portional to the duration of radiation.

Conodonts contain very low concentrationsof radioactive elements. Their ESR spectrawere therefore induced by natural backgroundradiation, i.e. cosmic rays and radiation fromradioactive elements present in the host-rocks.The ESR spectra obtained from the conodontsinvestigated do not indicate such a simpledependence. It appears that the spectral struc-ture is influenced by both time and temperature

[Ch. 14 Sec. 14.5]

and that the observed signal intensity is depen-dent upon both the radiation dose received bythe sample and the temperature.

samples (cf. Figs. 1-radiation persistingnecessary to produresponsible for sign

(a) Influence oftimeAlthough a dependence of the signal intensitieson the sample age was not observed, the spec-tral structure enables a subdivision into threegroups to be made. Spectra obtained fromTriassic conodonts are distinct in that signal A isnot exhibited. Only signal B is present, withsignals C and D being either very weak orabsent (Fig. 14.3). The second category of spec-tra consists of Devonian and Carboniferousconodonts. This category is characterized by thepresence of peak B, and also signals A, C and Dwhich are usually strong although, in somesamples, signals A or C may be absent. Theabsence of the signals is more a function ofheating than time.

The third group consists of the spectra ofOrdovician conodonts in which signals C and Dare very weak relative to the strong signals ofpeaks A and B (see Figs. 14.3 and 14.4).

®

(b) Temperature influenceTwo samples, samples 1 and 4, were heated inopen air from 100-1000°C for a period of0.5-96h. The resultant thermal annealingcaused changes in the intensity of particularsignals, with eventual disappearance of signalsexcept peak D, the intensity of which hadalmost doubled by a temperature of 1000°C (cf.Table 14.3 and Fig. 14.4). Because thermalannealing generates the decay of signals A, Band C, the intensity of these signals in alteredconodonts with an advanced thermal historywill be proportional to the time of the lastgeological upheaval and not to the total age ofthe sample. For such conodonts, the intensity ofsignal D will always be greater than that pro-duced by the background radiation during thetotal geological age of the sample.

Signal A, absent in the spectra obtainedfrom Triassic conodonts (even those which areunaltered), occurs in the spectra of Palaeozoic

®-----1

Fig. 14.3 - ESlshowing a depei

~--------~

!S [Ch. 14 Signal intensity as a function of time and temperatureSec. 14.5]

ial intensity is depen-:ion dose received byrarure.

samples (cf. Figs. 14.3 and 14.5). It appears thatradiation persisting for longer than 225ma wasnecessary to produce the paramagnetic centresresponsible for signal A. Therefore, all Palaeo-

zoic conodonts which do not emit peak A musthave been heated at a time after the Carbonifer-ous Period.

f the signal intensitiesobserved, the spec-

ubdivision into threeectra obtained frominct in that signal A isal B is present, witheither very weak or:ond category of spec-I and Carboniferouscharacterized by the

lsosignals A, C and D~ although, in somemay be absent. Themore a function of

@

/B/

of the spectra ofhich signals C and Dthe strong signals ofl-t.3 and 14.4).

®

emd 4. were heated inI =C for a period ofthermal annealing

nensity of particularappearance of signalsensity of which haderature of 1000QC(cf.

. Because thermalIecay of signals A, Btese signals in alteredneed thermal historythe time of the lastlot to the total age ofants, the intensity of

rreater than that pro-Iradiation during the! sample.the spectra obtainedeven those which arespectra of Palaeozoic

/AB/

1mTL..--.I

235

/0

I~li

Fig. 14.3 - ESR spectra for conodonts from Triassic, Carboniferous, Devonian and Ordovician deposits,showing a dependence of the spectrum structure upon the age of sample. The circled numbers denote the

investigated conodont samples (see Table 14.1).

236 The electron spin resonance technique in conodont studies [Ch. 14

Table 14.3 - Changes in the intensity of ESRsignals present in the spectra of conodonts,resulting from the influence of temperature(data based on the experimental heating of twoconodont samples (samples 1 and 4) to100°C,IS0°C and 200°C for 8h, to 500°C for3h, and to 1000°C for 6h.

Change in intensity at the followingtemperatures

a temperature of 500°C. Upon closer examin-ation, signal B is shown to be a band consistingof two weakly separated signals, indicated B'and B" (cf. Fig. 14.6). With increasing CA!values, an increase in the intensity of signal B" isnoted in relation to signal B'. Only one of theinvestigated samples, sample 9, departed fromthis trend, by exhibiting a signal B structuresimilar to that of conodonts with a CA! of 3.5 inspite of the sample colour corresponding to CA!2.5.

A No ~ ~ 0 0change

B No No No 0 0change change change

C t t t 0 0D No No No t t

change change change

Signal 100°C 150°C 200 °C 500°C 1000 °C It appears that the absence of a precisequantitative correlation between the intensityof ESR signals and the conodont CAI value is aresult of the thermal instability of the paramag-netic centres responsible for signals A, Band C(cf. Table 14.3), coupled with the fact that theintensity of the ESR signal is a combined func-tion of both the radiation time and the thermalhistory of the conodonts.

~ ,decrease; t ,increase; 0, absent.

14.6 COMPARISON OF ESR SPECTRAWITH CONODONT CAI VALUES

Although a precise correlation between theintensity of ESR signals and conodont CAIvalues has not been recorded, nevertheless theESR spectra of conodonts with an identical CAIvalue do show some similarities. These similari-ties are in accord with data which we obtainedfrom the experimental heating of conodonts.The spectra of conodonts which have a CAIvalue of 1 show signals C and D to be alwaysweaker than signal B, or to be absent, e.g. theTriassic samples. With higher CA! values, anincrease in intensity of peaks C and D is initiallyobserved. Signal C decays in conodonts with aCA! of 3.5 or higher, whereas both signals Dand Bare strong (Fig. 14.5).

The structure of signal B shows the strongestcorrelation with CAI value. The observation issurprising as experimental heating of conodontsdoes not indicate that signal B is responsible forconodont colour. This is why signal B decays at

14.7 EFFECT OFMICROMORPHOLOGICALCOMPOSITION

Pietzner et al. (1968) showed that there aredifferences in the chemical compositions of theconodont crown and base. The basal filling ismore fine grained and contains a higher con-centration of trace elements; for example,yttrium can be enriched in the base by a factor of20 greater than that in the crown.

Only in one sample investigated (sample 7,from the Frasnian deposits of the Holy CrossMountains) were a large number of conodontsobserved in which the crown was attached to thebase. The sample was divided into two portions,one with conodont crowns only, and the other inwhich crowns were attached to bases. Bothportions were investigated by ESR spectros-copy. The portion containing crowns attachedto the bases yielded spectra with signals whichwere all stronger than the portion comprisingcrowns alone; the intensities of signals A, BandC were twice as strong, and signal D was fivetimes as strong. The greater organic content in

Sec. 14.8]

the basal filling i cincrease in the inten

Therefore it is inodont crowns alonecopy. This is of adconcentration of tra

Fig.l-U-E

s [Ch. 14 Sec. 14.8]

';pon closer examin-be a band consistingsignals, indicated B'Ith increasing CAIuensity of signal B" isB'. Only one of theple 9, departed froma signal B structureswith a CAI of 3.5 inorresponding to CAI

the basal filling is one reason for the markedincrease in the intensity of signal D.

Therefore it is important to investigate con-odont crowns alone when using ESR spectros-copy. This is of additional importance, as theconcentration of trace elements in the bases is

bsence of a preciseerween the intensityodont CAI value is adlity of the paramag-JI signals A, Band Cwith the fact that theI is a combined func-time and the thermal

Qc

:AL

owed that there are1compositions of the!. The basal filling istains a higher con-

rents; for example,the base by a factor ofcrown.vestigated (sample 7,

of the Holy Crossmmber of conodontsm was attached to theled into two portions,only, and the other inihed to bases. Both:d by ESR spectros-ling crowns attachedra with signals whiche portion comprisinges of signals A, Bandmd signal D was five:er organic content in

B~

1 mT'----'

Application 237

most probably due to later (post-mortem?)inputs (Pietzner et al., 1968).

14.8 APPLICATIONESR spectroscopy was proposed as a datingtechnique for conodonts by Morency et at.(1970). The technique consists of subjecting the

D~

/

~

Fig. 14.4 - ESR spectrum for Ordovician conodonts (sample 1) and its changes after heat treatment.

238 The electron spin resonance technique in conodont studies [Ch. 14

conodonts to small doses of laboratory y-radia-tion in order to establish the dependence ofsignal growth upon the radiation dosage. If thesignal growth is linear, then it is possible to

extrapolate to obtain the geological age of thesample if the total radiation dose is known (cf.Zeller et al., 1967).

This investigation, however, has shown

@CA/= 2--------=--

1 mT

Fig. 14.5 - ESR spectra of conodonts with different CAI values. Note the distinct increase in signals Band Dfor conodonts with a maximum thermal history. The circled numbers denote the investigated conodont

samples (see Table 14.1).

Sec. 14.10]

@ -........J

B'-

G) )@ ~

® /@)

® /

®Fig. 14.6 - Consignal B with IXnumbers deno e

samples

that, for the 17 COD

signal intensity is amost definitely, teevent, even of shortof signals A, B argrowth of signal :cfrom the ESR Spedmisleading. In addnPalaeozoic conodoappeared. This diffintensity as a result

[Ch. 14 Sec. 14.10] References

~logical age of thedose is known (cf. @~

S'_(\. ~ ~'ever, has shown

CD

<: @

;./ ""2®

-----@)

-CAI =3.5

\ ""2-r- ®

-CAI =4

@:\",,4--- Fig. 14.6 - Correlation of the structure of

signal B with conodont CAI. The circlednumbers denote the investigated conodont

samples (see Table 14.1).

ia signals Band Dsagated conodont

that, for the 17 conodont samples studied, thesignal intensity is a function of both time and,most definitely, temperature. As a heatingevent, even of short duration, produces a decayof signals A, Band C, with a simultaneousgrowth of signal D, then any dates obtainedfrom the ESR spectra of conodonts can be verymisleading. In addition, during studies of EarlyPalaeozoic conodonts, another difficulty hasappeared. This difficulty is a decrease in signalintensity as a result of the additional laboratory

239

radiation (cf. Morency et al., 1970). The effectwas observed when sample 1 had been sub-jected to a y-radiation dose of 0.17 x 106R.After the radiation, signals A, Band C disap-peared whilst signal D increased by a factor ofalmost 4. According to Vaz and Zeller (1966),the decrease in signal intensity in response toadditional radiation occurs with saturation ofparamagnetic centres. In this case, the numberof unpaired electrons responsible for the ESRsignals tends to decrease.

As a consequence, we do not recommendESR spectroscopy as a technique for age-deter-mination of conodonts. It is recommendedinstead that ESR spectroscopy be used for dat-ing the last heating event, i.e. most frequentlythe age of the completion of the last upheaval ofthe conodonts.

ESR spectra can yield useful informationabout the heat treatment of conodonts,especially in cases of heating to less than 200QCfor very short periods of time, and in which nocolour changes have been produced in theconodonts.

ESR spectroscopy has a potential appli-cation in the testing and correlation of CAIvalues of conodonts from different host-rocks,or in situations where the conodont colour hasbeen modified by the lithology, diagenesis and/or weathering.

14.9 ACKNOWLEDGEMENTSWe would like to thank Dr. J. Dzik and Dr. K.Zawidzka for providing some conodont samplesfor this study. Thanks are also due to ProfessorDr. A. Radwariski and Dr. A. Gize who criti-cally read the manuscript and offered helpfulsuggestions.

14.10 REFERENCESAtherton, N. M. 1973. Electron Spin Resonance, Halsted

Press, London, 1-430.Cubbitt, J. M. and Wilkinson, J. G. 1976. A classification

study of shales in Kansas using electron-spin resonancespectroscopy. Journal of Mathematical Geology, 8 (3),337-344.

Drago, R. S. 1977. Physical Methods in Chemistry, W. B.Saunders, New York, 1-660.

240 The electron spin resonance technique in conodont studies [Ch. 14

Epstein, A. G., Epstein, 1. B. and Harris, L. D. 1977.Conodont color alteration - an index to organic meta-morphism. U.S. Geological Survey Professional Paper,995,1-27.

Fahraeus, L. E. and Fabraeus-van Ree, G. E. 1985. Histo-morphology of soft tissue conodont matrix. In R. 1.Aldridge, R. L. Austin, andM. P. Smith (Eds.), FourthEuropean Conodont Symposium (ECOS N),Abstracts, Private publication, University of South-ampton,lO-ll.

Friedlander, H. Z., Saldick, 1. and Frink, C. R. 1963.Electron spin resonanace spectra in various clay miner-als. Nature, 199 (4888), 61-62.

Garrison, E. G., Rowlett, R. M., Cowan, D. L. andHolroyd, L. V. 1981. ESR dating of ancient flints.Nature, 290, (5801), 44-45.

Gilinskaya, L. G., Gerasimov, E. K., Sukhoverkhova, M.B. and Pospelova, L. N. 1982. ESR spectra of apatitesfrom metamorphozed rocks (in Russian). Proceedingsof the USSR Acadamy of Sciences, Geological Series,3, 100-112.

Gilinskaya, L. G. and Shcherbakova M. 1. 1975. Investi-gations of structural damage in apatite by electron spinresonance spectroscopy (in Russian). In Physics ofapatite, Nauka, Novosibirsk, 7-63.

Hutton, D. R. and Troup, G. 1. 1966. Paramagnetic reso-nance centres in amethyst and citrine quartz. Nature,211, (5049), 62l.

Ikeya, M. 1975. Dating a stalactite by electron paramagne-tic resonance. Nature, 225, (5503), 48-50.

Ikeya, M. and Miki, T. 1980. Electron spin resonancedating of animal and human bones. Science, 207 (4434),977-979.

Low, W. and Zeira, S. 1972. ESR spectra of Mn2+ in heat-

treated aragonite. American Mineralogist, 57 (7-8),1115-1124.

Morency, M., Emond, P. L. and von Bitter, P. H. 1970.Dating conodonts using electron spin resonance: apossible technique. Kansas Geological Survey Bulletin,199 (1),17-19.

Pietzner, H., Vahl, 1.,Werner, H. and Ziegler, W. 1968.Zur chemischen Zusammensetzung und Mikromor-phologie der Conodonten. Palaeontographica A, 128,115-152, 10 plates.

Robins, G. V., Seeley, N. F., McNeil, D. A. C. andSymonsM. R. C. 1978. Identification of ancient heat treatmentin flint artefacts by ESR spectroscopy. Nature, 276(5689),703-704.

Schindler, P. and Ghose, S. 1970. Electron paramagneticresonance of Mn2+ in dolomite, and magnesite, andMrr'" distribution in dolomites. American Mineralo-gist, 55 (11-12),1889-1896.

Symons, M. R. C. 1978. Chemical and Biochemical Aspectsof Electron Spin Resonance Spectroscopy, Van Nos-trand Reinhold, New York, 1-185.

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Wakeman, S. and Carpenter, R. 1974, ESR spectra ofmarine and freshwater manganese nodules. ChemicalGeology, 13, (1), 39-47.

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15Temperatuand distribJ. E. Geitgey and T. R..«

Recent studies invrsurements of eoanalyses may provitemperature signresults at presenOrdovician-Pennsjcompilation of a Paperature curve wviously described qPalaeozoic palaeod

There is a mar Of

between the isotinferred palaeotemof fluctuation of eobution. In partiinferred higher orture (i.e. Ibexian. ~and Triassic intervbution appear toConversely, duringreasing palaeotemjCincinnatian, Ca:intervals), diversireduced.

The observed ctemperature was ~