WATERWATERW A E\ ERWATERW ATERWATERWATER,

Wti 11.

- • •

PROJECT COMPLETION

REPORT NO. 367X

Survey of

SrVSr86

Ratios in

Stream and

Ground Waters

of Ohio

By

Paul Pushkar4

John Steele

Alan Stueber

Dwight Baldwin

and

Nicholas Beskid

1971

United States Department

of the Interior

CONTRACT NO.

A 020-OHIO

AA-14-01-0001-1855

State of Ohio Water Resources Center

Ohio State University

v

SURVEY OF Sr87/Sr86 RATIOS

IN STREAM AND GROUND WATERS OF OHIO

Paul Pushkar and John Steele

Department of GeologyWright State University

Dayton, Ohio

Alan Stueber, Dwight Baldwin and Nicholas Beskid

Department of GeologyMiami University

Oxford9 Ohio

Final Report

Submitted to: Water Resources Center The Ohio State University

Office of Water Resources Research The United States Department of Interior

Project No. 14-01-0001-0hio

June, 1971

TABLE OF CONTENTS

Page

LIST OF TABLES iii

LIST OF FIGURES iv

ACKNOWLEDGMENTS v

ABSTRACT v i

INTRODUCTION 1

SAMPLE COLLECTION 5

ANALYTICAL METHODS 6

Specific Conductance 6Strontium Concentrations 6Sodium Concentrations . 11Strontium Isotopic Analyses 11

INTERPRETATION OF RESULTS 14

SUMMARY AND CONCLUSIONS 21

REFERENCES CITED 23

LIST OF TABLES

Table Page

1. SAMPLE LOCATIONS AND LITHOLOGIC DESCRIPTIONS, Sr ANDNa CONCENTRATIONS, AND SPECIFIC CONDUCTANCE MEASURE­MENTS 7

2. STRONTIUM AND SODIUM ANALYSES OF THE UNITED STATESGEOLOGICAL SURVEY STANDARD WATER REFERENCE SAMPLE

NO. 26 12

3. Sr87/Sr86RATI0S OF WATER SAMPLES 15

4. ANALYSES OF EIMER & AMEND SrC03 STANDARD andDUPLICATE ANALYSES OF WATER SAMPLES 16

LIST OF FIGURES

Figure Page

1. GROWTH OF Sr87 IN SEDIMENTARY ROCKS 2

2. GEOLOGIC MAP OF OHIO 18

3. MAP OF OHIO SHOWING WATER SAMPLE LOCATIONS, MODE OFOCCURRENCE, AND Sr87/Sr86 RATIOS 20

IV

ACKNOWLEDGMENTS

We wish to acknowledge the assistance of the Departments of Geology at

Miami University and Wright State University for providing equipment and lab­

oratory facilities necessary for the completion of this project. Professor

Gunter Faure, The Ohio State University, permitted the use of his laboratory

for the calibration of chromatography columns with a Sr89 radioactive tracer.

We also acknowledge his helpful advice on many aspects of this project. We

wish to thank Mrs. Ruth E. McLeod of Miami University for typing the final

manuscript.

ABSTRACT

A total of 19 Ohio stream and ground waters have been sampled and ana­

lyzed for total Sr and Sr87/Sr86 isotopic ratios in an attempt to evaluate the

potential usefulness of the Sr87/Sr86 ratio as a tracer of water provenance.

Samples were collected in order to provide a wide geographic distribution and

a variety of contacted lithologies. The measured Sr87/Sr86ratios range from

about 0.708 to 0.713, with the higher ratios occurring in eastern Ohio and the

lower ratios in the west. We believe that this trend reflects the change in

the dominant lithology of the Paleozoic sediments across Ohio. In the east

clastic sediments predominate, whereas in the west limestone becomes a more

important component of the sedimentary sequence. Most limestones of Paleozoic

age or younger are known to have Sr87/Sr86 ratios of approximately 0.708, where­

as shales have a wide range of higher values. Thus the Sr87/Sr86 ratios in

western Ohio may reflect the greater proportion of limestone in the sedimentary

column in this area. We feel that the demonstrated variability of the Sr87/Sr86

ratio in Ohio waters, and its apparent dependence on lithology in the sampling

areas, are sufficiently encouraging to warrant further study of the applica­

tion of this parameter as a tracer in water studies.

VI

INTRODUCTION

Natural var iat ions in the isotopic r a t i o Sr8 7 /Sr8 6 have been i n v e s t i ­

gated by geochemists for approximately the past ten years. Such var iat ions

arise because of the production of Sr87 due to the radioact ive decay of Rb87.

Natural ly-occurr ing strontium has four isotopes, but only Sr87 can be produced

through radioact ive decay and thus vary in i t s re la t i ve abundance. The abun­

dance of Sr87 is conveniently expressed as the r a t i o S r 8 7 / S r 8 6 , the value of

which in any material depends upon two fac tors :

(1) The Rb/Sr elemental r a t i o in the mater ia l . Materials which contain

large amounts of Rb, and therefore of Rb87, re la t i ve to strontium w i l l

generate larger amounts of Sr87 over a given period of time than

materials with low Rb/Sr-rat ios. The Sr8 7 /Sr8 6 r a t i o , therefore, is

expected to be higher in materials w i th high Rb/Sr ra t i os .

(2) The geologic age of the mater ia l . The older a ma te r ia l , the more time

has been avai lable for Rb87 t o decay in to Sr8 7 , so tha t the Sr8 7 /Sr8 6

r a t i o w i l l be higher than tha t in a comparable younger mater ia l .

In general, Rb-rich rocks such as shales have r e l a t i v e l y high present

Sr8 7 /Sr8 6 ra t ios whereas Rb-poor rocks such as carbonates have low Sr 8 7 /Sr8 6

ra t ios today. These general izations are i l l u s t r a t e d by the typ ica l growth

curves for shales and carbonates presented in Figure 1. Once such d i f f e ren t

Sr8 7 /Sr8 6 ra t ios are produced in natural mater ia ls , they are unaffected by

chemical and physical processes. Thus they d i f f e r from isotop ic rat ios o f

l i gh te r elements such as carbon or sulphur, which can be i so top ica l l y f r ac ­

t ionated by such processes. The Sr 8 7 /Sr 8 6 r a t i o in any natural system today

Fi gure 1

GROWTH OF Sr87 IN SEDIMENTARY ROCKS

<Sr87/Sr8% = Xt 87 Sr

S r 8 6 720­

•710- LIMESTONE (Rb/Sr « 0 )

• I 1 I I f

600 500 400 300 200 100 0

TIME (m.y.)

I -e I 0 I S I D I M t P I P I H I Jt I K lR«c«fril

GROWTH OF Sr IN SEDIMENTARY ROCKS

can change only by the addition of strontium having a different Sr87/Sr86 rat io

or by the decay of Rb87 with the passage of time. In the lat ter case, the

ha l f - l i f e of Rb87 is so great (50 x 109 years) that the additional accumulation

of radiogenic Sr87 is inconsequential over time spans of interest to man. Re­

cent reviews of strontium isotope geochemistry have been presented by Hamilton

(1965, 1968).

Because present Sr87/Sr86 ratios are not subject to measurable change

except by mixing, they can be used as a "label11 to trace the origin of certain

materials. For example, al l modern oceans contain dissolved strontium with a

Sr87/Sr86 rat io very close to 0.7090. Thus a l l materials formed today solely

by precipitation from sea water, such as evaporites, biologic calci te* and

most carbonate rocks, also have Sr87/Sr86 ratios of 0-7090. Continental rocks,

on the other hand, have a wide range of Sr87/Sr86 rat ios. The average value

for the s ia l ic crust today is probably close to 0.725. Therefore, i f an

oceanic sediment consists of a detr i ta l component formed from the weathering

of the continental crust and a calcium carbonate component formed by biologi­

cal precipitation from sea water, i ts Sr87/Sr88 rat io should be intermediate

between 0.709 and 0.725. I f the sediment could be physically separated into

i ts two components and each component analyzed for i t s Sr87/Sr86 ra t io , these

dif ferent sources could be demonstrated. Such studies have been carried out

successfully (Dasch, H i l l s , and Turekian, 1966).

The labeling of a natural material by means of i t s Sr87/Sr86 rat io

should be applicable to a study of surface and ground waters. In this case *

the rat io may indicate the areas where the waters had the i r origin or through

which they subsequently migrated. For example, consider a rain fa l l ing upon a

watershed. A portion of i t enters the soi l or bedrock, in f i l t ra tes to the

zone of saturation, and becomes ground water. As this water moves through

permeable and porous aquifers, it commonly acquires a high concentration of

total dissolved solids. Suppose that bedrock underlying the watershed consists

of two distinct lithologies typical in the state of 0hio5 a shale and a lime­

stone. Sr87/Sr86 ratios in these two lithologies today may be 0.725 for the

shale and 0.708 for the limestone. The rain water, after entering both rock

types, will leach strontium from them; the ground water in the shale will

leach strontium with a Sr87/Sr86 ratio of 0.725, and the ground water in the

limestone will leach strontium with a Sr87/Sr86 ratio of 0.708. After subse­

quent vertical and/or horizontal movement of these ground waters, sampling and

Sr87/Sr86 analysis might be used to trace the history of this movement and

possibly identify the ultimate provenance. For example, if water from a well

within the shale has a Sr87/Sr86 ratio of 0.709, this would indicate that the

water had either originated in or had previously flowed through the limestone

before entering the shale. On the other hand, if a stream draining both the

shale and limestone has a Sr87/Sr86 ratio of 0.720, this would indicate that

most of the stream water is derived from the shale.

We have attempted to evaluate the potential usefulness of the Sr87/Sr86

ratio as a tracer in the study of stream and ground waters in the state of

Ohio. In order to make practical application of this concept, it is necessary

first to demonstrate that the Sr87/Sr86 ratios in such waters within a given

area are sufficiently variable, and that such variations can be related to

lithologic type of bedrock and overburden. This aspect of the overall concept

has been evaluated in the present report by making a reconnaissance study of

stream and ground waters throughout Ohio.

SAMPLE COLLECTION

Collection stations for sampling both surface and ground waters were

chosen in order to provide water from as many lithologies and hydroiogic en­

vironments as exist in Ohio. A suite of samples was collected extending from

the Upper Ordovician through the Pennsylvanian-Permian Systems, south of the

southern l imi t of Pleistocene glaciat ion, in order to determine total Sr con­

centrations and Sr isotope ratios in areas not covered by glacial t i l l . Sur­

face and ground water samples were also obtained from similar lithologies north

of the glacial boundary.

Water samples were collected at 40 stations across the state. Thirty-

one of these were collected during July and August, 1970. Four were obtained

in February and five in May, 1971. The majority were collected during the dry

summer months in order to maximize the contribution of ground water to total

stream discharge. Eastin and Faure (1970) report that strontium isotopic

ratios of waters of the Olentangy River, Ohio, decrease with increasing r iver

discharge. This decrease is interpreted as a di lut ion of the ground water

component of the r iver discharge by rain water having a low isotopic ra t io .

In order to obtain a close approximation of the strontium isotopic composition

of ground water within a given basin,, low-flow samples were therefore collec­

ted.

All samples were collected in polyethylene bottles. Each bottle was

washed three times with the water to be collected before f ina l ly being f i l l e d .

Waters for isotopic analysis were collected in 9 .5- l i te r containers, whereas

those for strontium, sodium, and specific conductance determinations were col ­

lected in one-l i ter containers. After obtaining specific conductance values

in the laboratory, the water intended for strontium and sodium determinations

was acidified with glacial acetic acid in order to prevent possible precipita­

tion of strontium.

ANALYTICAL METHODS

Specific Conductance

Values for specific conductance were obtained for each of the 40 water

samples using the Beckman SoluBridge, model RD-125I. Approximately 200 ml of

the one-liter sample were poured into a 250 ml beaker. The specific conduct­

ance electrode, after being washed twice in deionized water, was placed in the

water sample. This modified Wheatstone bridge was then balanced to obtain the

specific conductance of the water sample. The accuracy of the instrument was

checked by preparing a 600 mg/liter standard sodium chloride solution and com­

paring the known conductance of this standard solution with the reading of the

instrument. The results of the specific conductance determinations are pre­

sented in Table 1.

Strontium Concentrations

The procedure used in determining strontium concentrations in the

water samples was that of Fishman and Downs (1966), employing atomic absorp­

tion spectrophotometry. The analyses were carried out on a Perkin-Elmer Model

303 unit. In order to control the decrease in strontium ionization in the

flame due to the presence of sodium and potassium, 1000 mg/liter of potassium

was added to both samples and standards. Interference due to the presence of

aluminum, phosphate, and silica was eliminated by the addition of a lanthanum

solution, such that the samples and standards contained 1% lanthanum. The

strontium concentrations of all 40 water samples are presented in Table 1.

Table 1

SAMPLE LOCATIONS AND LITHOLOGIC DESCRIPTIONS,Sr AND Na CONCENTRATIONS, AND SPECIFIC CONDUCTANCE MEASUREMENTS

Sample and Date Collected

Location and Lithologic Description

Srgo-1 Oxford well water, Butler Co., S. W. Ohio; glacial 7/7/70 outwash

Srgt-2 Hopewell Church Spring, Butler Co,, S. W. Ohio; 7/7/70 glacial t i l l and gravel

Srg-3 Dare Farm Spring, Butler Co., S. W. Ohio; spring 7/7/70 issuing from r iver terrace deposits

Srg-4 Water from hand-dug well on Ticknor Farm, Ashta­8/13/70 bula Co., south of Austinburg in N. E. Ohio; water

believed to be from glacial deposits

Srg-5 Spring at Campfire Girls Camp, south of Austin­8/13/70 burg, Ashtabula Co., N. E. Ohio; water believed

to be from glacial deposits

Srg-6 Water from hand-dug well 2-1/2 miles west of 5/1/71 Ashley, Delaware Co., Ohio; water believed to be

from glacial deposits

SrL-1 Spring south of West Union, Adams Co., S. W. Ohio; 7/27/70 water issuring from Devonian limestone

SrL-2 Spring water from Yellow Spring; Yellow Springs, 7/29/70 Greene Co., S. W. Ohio; water from Silurian

limestone, t i l l sheet covers area

SrL-3 Spring near St. Paris, Champaign Co., west­8/12/70 central Ohio; water believed to be from both

glacial outwash and upper Silurian limestone

Sr Concentration

(mg/1)

0.22

0.10

0.19

0.25

0.12

0.52

0.13

0.16

0.08

NaConcentration

6.40

4.74

3.48

15.75

11.16

102.0

3.45

17.81

Specific Conductance

(u mohs)

575

560

560

585

280

1,100

1,420

685

500

Table 1 (cont.)

Sampleand Date Location and Lithologic DescriptionCollected

SrL-4 Blue Hole Spring, C a s t i l i a , Erie Co., north-central 8/12/70 Ohio; Devonian limestone, t i l l sheet blankets area

SrD-1 Water from well in Veto, Washington Co., S. E. Ohio; 7/29/70 water from Penn.-Permian Dunkard Group e last ics

SrD-2 Spring on Becker Farm, N. E. Washington Co., S. E. 7/29/70 Ohio; Penn.-Permian Dunkard Group elast ics

SrD-3 Spring on Hamilton Farm, S. of Bloomfield, N. E. 7/29/70 Washington Co., S. E. Ohio; Penn.-Permian Dunkard

Group e last ics

SrSh-1 Spring 1/2 mile W. of Mineral Springs, Adams Co., 7/27/70 S. W. Ohio; water issuing from Devonian Ohio Black

Shale

SrSh-2 Well water col lected 1-1/2 miles E. o f Rarden on 7/27/70 Ohio Rt. 73, Scioto Co., south-central Ohio; water

from Devonian Ohio Black Shale

SrSh-3 Well water, approximately 3 miles west of Ashley, 5/1/71 Delaware Co., Ohio; water from Devonian Ohio Black

Shale

SrS-1 Spring, approximately 5 miles N. E. of West Union, 7/27/70 Adams Co., S. W. Ohio; water from calcareous sand­

stone, upper S i lu r ian

SrS-2 Spring located approximately 2 miles S. E. of 7/27/70 Fawcett, N. E. Adams Co., S. W. Ohio; water from

calcareous sandstone, upper S i lu r ian

SrS-3 Spring at Sinking Springs, Ohio, Highland Co., 7/28/70 S. W. Ohio; water from upper S i lur ian

Sr Concentration

(mg/1)

8.37

0.31

0.04

0.13

0.20

0.24

9.84

0.06

0.07

0.07

Na Concentration

(mg/1)

14.75

16.75

16.62

3.31

6.68

17.31

2.56

2.65

17.81

Specif ic Conductance

(\i mohs)

1,750

320

140

255

570

445

1,450

630

750

690 CO

Table 1 (cont.)

Sampleand Date Location and Lithologic DescriptionCollected

SrS-4 Well water approximately 2-1/2 miles E. of Pratts 7/28/70 v i l l e , Vinton Co., east-central Ohio; P o t t s v i l i e -

Allegheny Formations

SrCk-1 Ohio Brush Creek at gaging s ta t ion on State Rt. 7/27/70 348, Adams Co., S. W. Ohio

SrCk-2 Tr ibutary to Turkey Creek, 1/2 mile E. of Mineral 7/27/70 Springs, Scioto Co., S. W. Ohio

SrCk-3 Scioto-Brush Creek on Rt. 73, Adams Co., south­7/28/70 central Ohio

SrCk-4 L i t t l e Hocking River at crossing Rt. 76 N. of 7/29/70 Por te r f ie ld in S. E. Washington Co.

SrCk-5 L i t t l e Miami River, S. of C l i f t on on Rt. 72, 7/29/70 Greene Co., S. W. Ohio

SrCk-6 Mad River at Dal1 us Road, approximately 4 miles 8/12/70 S. W. of Urbana, Champaign Co., west-central Ohio

SrCk-7 Nett le Creek, approximately 3 miles S. W. of 8/12/70 Urbana, Champaign Co., west-central Ohio

SrCk-8 Mad River at gaging s ta t ion on U. S. Rt. 36, ap­8/12/70 proximately 1 mile W. of Urbana on Rt. 36, Cham­

paign Co., west-central Ohio

SrCk-9 Kings Creek on Rt. 296 near confluence with Mad 8/12/70 River, approximately 2 miles N. of Urbana, Cham­

paign Co., west-central Ohio

SrCk-10 Mad River on Rt. 68, S. of L ibe r t y , Logan Co., 8/12/70 west-central Ohio

Sr Concentration

(mg/1)

0.51

0.08

0.06

0.13

0.17

1.37

0.76

1.70

0.43

0.35

0.52

Na Concentration

(mg/1)

25.63

4.52

2.71

5.88

16.44

5.85

7.20

6.00

3.82

3.58

3.54

Speci f i c Conductance

(y mohs)

400

400

155

755

285

635

685

500

650

600

640

Table 1 (cont.)

Sample Sr Na Specific and Date Location and Lithologic Description Concentration Concentration Conductance Collected (mg/1) (mg/1) (y mohs)

SrCk-11 8/12/70

SciotoOhio

River at Kenton, Hardin Co., north-central 12.35 31.13 880

SrCk-12 8/13/70

Grand River,N. E. Ohio

S. of Austinburg, Ashtabula Co., 0.13 20.69 370

SrC-1 7/29/70

Water from pond at base ofcoal mining, 5 miles W. ofCo., central Ohio

cut made for open-pit Cumberland, Muskingum

1.92 15.05 2,900

SrCk-13 2/15/71

T i f f i n River,N. W. Ohio

E. of Defiance, Defiance Co., 0.40 — 300

SrCk-14 2/15/71

Maumee River,N. W. Ohio

E. of Defiance, Defiance Co., 0.40 — 410

SrCk-15 2/21/71

Great Miami, Mi ami town, Hamilton Co., S. W. Ohio 0.27 — 300

SrCk-16 2/15/71

Lake St . Mary's, Celina, Mercer Co., N. W. Ohio 0.41 — 445

SrCk-17 5/1/71

WhetstoneOhio

Creek, W. of Ashley, Delaware Co., central 1.46 — 805

SrCk-18 5/1/71 Kill buck Creek, Wooster, Wayne Co., N. E. Ohio

0.21 — 585

SrCk-19 5/1/71 Sippo Creek, Massi l ion, Stark Co., N. E. Ohio

0.10 640

11

As a check on accuracy and reproducibility of the strontium determina­

t ions, the United States Geological Survey standard water reference sample

number 26 was run with each set of water samples analyzed. The values ob­

tained (Table 2) compare favorably with the accepted value of 0.844 mg/l i ter,

and a l l are within the standard deviation of 0.151 mg/l i ter determined by 20

independent laboratory analyses.

Sodium Concentrations

The sodium concentrations of the water samples were also obtained by

atomic absorption spectrophotometry, employing the procedures of Fishman and

Downs (1966). Other elements present in natural waters do not interfere with

sodium determinations. The results of the sodium analyses are presented in

Table 1.

The accuracy and reproducibil ity of the sodium analyses were also

evaluated by analyzing the U. S. G. S. standard water reference sample.

Values obtained (Table 2) are in good agreement with the accepted value of

185.7 mg/ l i ter , and fa l l within the standard deviation of 5.5 mg/l i ter, deter­

mined by 30 independent laboratories.

Strontium Isotopic Analyses

The chemical separation of dissolved strontium from the water samples

was carried out at Wright State University. The procedures employed evolved

somewhat with time, so that the ear l ier separations were handled somewhat d i f ­

ferently than the later separations. The procedures used in the later separa­

tions are described below.

Approximately one l i t e r of the water sample was f i l te red into a reser­

voir f i t t ed into the top of a glass column used for cation-exchange chromatog­

raphy. The columns employed are approximately 2 cm in diameter and approxi­

mately 30 cm in length. They are f i l l e d with Bio-Rad AG 50W-X8 100-200 mesh

12

TABLE 2

STRONTIUM AND SODIUM ANALYSES OF THEUNITED STATES GEOLOGICAL SURVEYSTANDARD WATER REFERENCE SAMPLE

NUMBER 26

Date Sr (mg/1) Na (mg/1)

8/5/70 0.820

8/20/70 0.868

8/21/70 0.868

8/25/70 0.890

9/28/70 191

9/28/70 186

2/27/71 0.862

13

analytical grade cation exchange resin. The f i l te red water was allowed to

drain through the column. Tests using small amounts of a Sr89 radioactive

tracer indicate that a l l the dissolved strontium was sorbed within the top few

cm of the resin column. I f the strontium concentration in the water was very

low, additional water was f i l te red into the reservoir and allowed to drain

through the column. The column was then eluted with 2.00 N HC1, prepared by

bubbling analytical grade hydrogen chloride gas through t r i p l e -d i s t i l l ed water,

obtained from the McPherson Laboratories at the Ohio State University. Previ­

ous calibrations have determined that 500 ml of acid are required to elute the

strontium through the resin and to begin to elute i t from the bottom of the

column. At this point a vycor beaker was placed beneath the column and the

next 400 ml of acid was collected. Tests with the Sr89 tracer showed that

most of the strontium in the sample was contained within this fraction. The

acid was then evaporated to dryness within a pyrex hood. The residue was of­

ten yellowish in color, probably because of resin washed from the column.

This was oxidized by adding a few ml of high purity n i t r i c and perchloric

acids and again evaporating to dryness within a pyrex hood. The residue was

then dissolved in n i t r i c acid, transferred to a 10 ml pyrex beaker, evaporated

to dryness, covered, labeled, and stored for isotopic analysis.

Water samples from carbonate terrains often give an abundant hygro­

scopic white residue which causes considerable outgassing during mass spec­

trometry. I t was found that passing such samples through the chromatography

column a second time essentially eliminates this problem.

The strontium isotopic compositions were determined on a 12-inch radius

of curvature, 90° sector, solid-source mass spectrometer, using double rhenium

filaments. The instrument is located at Miami University. The strontium frac­

tion separated from the water sample was dissolved in a few drops of di lute

14

NH03 and was evaporated onto one of the two rhenium filaments, both of which

had been pre-cleaned by heating in the mass spectrometer. After inserting the

double-filament source into the mass spectrometer and obtaining a suitable

vacuum, a stable strontium ion beam was produced by evaporation and ionization

of the strontium sa l t . After acceleration by an e lect r ic f i e ld of 3000 vo l ts ,

the ion beam was resolved into i t s characteristic mass components by magnetic

scanning. A typical analysis consisted of three charts, each representing 20

scans across the mass range 86 to 88. Peak heights were read from the charts,

and the average Sr87/Sr86 and Sr88/Sr86 ratios were calculated for each chart.

Mass fractionation corrections were applied by normalizing the average Sr87/

Sr86 ratios to a Sr88/Sr86 ra t io of 8.375. The normalized Sr87/Sr86 ratios

for the three charts were averaged and this value is reported for each analyzed

sample in Table 3.

The accuracy of the strontium isotopic analyses was evaluated by run­

ning the inter-laboratory Eimer and Amend SrC03 standard. Our results (Table

4) are in good agreement with those reported by other labs, which f a l l in the

range 0.7075 to 0.7085. The reproducibi l i ty of the Sr87/Sr86 ratios is i nd i ­

cated by duplicate analyses, including chemical processing, of two water

samples (Table 4). I t is clear that measured Sr87/Sr86 ratios which d i f fe r by

one part in 700 or more are certainly s igni f icant beyond the l imits of experi­

mental uncertainty.

INTERPRETATION OF RESULTS

This report essential ly represents a reconnaissance study of Sr87/Sr86

ratios in stream and ground waters of Ohio. The study was carried out in order

to ascertain the var iab i l i t y of this parameter in waters throughout the state,

15

TABLE 3

Sr87/Sr86 RATIOS OF WATER SAMPLES

SrCk-4

SrCk-5

SrCk-7

SrCk-10

SrCk-11

SrCk-13

SrCk-16

SrC-1

SrL-1

SrL-2

SrL-3

SrL-4

SrD-2

SrS-3

SrSh-1

Srg-5

SrD-1

SrS-4

Srg-1

Sample

L i t t l e Hocking River Washington Co.

L i t t l e Miami River Greene Co.

Nettle Creek Champaign Co.

Mad River Logan Co.

Scioto River Hardin Co.

T i f f i n River Defiance Co.

Lake St. Marys Mercer Co.

Cumberland pond Muskingum Co.

West Union spring Adams Co.

Yellow Springs Greene Co.

St. Paris spring Champaign Co.

Blue Hole spring Erie Co.

Becker spring Washington Co.

Sinking Springs Highland Co.

Mineral Springs Adams Co.

Austinburg spring Ashtabula Co.

Veto well water Washington Co.

Prattsvi l i e well water Vinton Co.

Oxford well water Butler Co.

Sr8 7/Sr8 6*

0.7130

0.7094

0.7089

0.7085

0.7087

0.7091

0.7090

0.7115

0.7129

0.7094

0.7078

0.7082

0.7130

0.7129

0.7125

0.7118

0.7130

0.7111

0.7084

* Normalized to Sr88/Sr86= 8.375.

16

TABLE 4

ANALYSES OF EIMER & AMEND SrC03 STANDARD

Date Sr87/Sr86

11/25/70 0.7082

12/5/70 0.7081

1/7/71 0.7085

3/8/71 0.7080

DUPLICATE ANALYSES OF WATER SAMPLES

Sample Sr 8 7 /Sr 8 6

SrSh-1 0.7125 0.7121

SrL-4 0.7084 0.7080

and possibly to relate any observed variations to the l i thologic type of the

bedrock and overburden in the sampling areas.

The common surface lithologies in Ohio are Paleozoic marine carbonates

and shales, as well as glacial t i l l which consists primarily of pulverized

local bedrock. Our general knowledge of the strontium isotopic compositions

of carbonates and shales is suff ic ient to allow us to predict that signif icant

differences in Sr87/Sr86 ratios exist in these l i thologies in Ohio today.

Marine carbonate rocks have very low Rb/Sr rat ios, so that their Sr87/Sr86

ratios have changed imperceptibly since deposition, and w i l l reflect the

strontium isotopic composition of the ocean at the time of their deposition.

For Paleozoic carbonates, the Sr87/Sr86 ratio w i l l be in the range 0-708 to

0.709. Shales, on the other hand, consist of detr i ta l Rb-bearing minerals,

and hence w i l l be enriched today in radiogenic Sr87. Composites of Paleo­

zoic shales have yielded Sr87/Sr85 values of about 0.718. Thus the potential

exists for signif icant differences in the Sr87/Sr86 ratios of Ohio waters.

Sr76/Sr86 ratios have been determined for a total of 8 surface waters,

8 spring waters, and 3 well-water samples (Table 3), The measured Sr87/Sr86

ratios range from about 0.708 to 0.713, a difference which is signif icant far

beyond the l imits of experimental error. Many of the samples contain Sr87

which is more radiogenic than that which would be contributed by marine car­

bonate rocks alone. We must now investigate whether these differences can be

related to the bedrock and overburden in the sampling areas.

A geologic map of Ohio is shown in Figure 2. The Paleozoic sedimentary

rocks exposed at the surface dip to the southeast, and increase in age from

east to west. In the east clast ic sediments predominate. The Pennsylvanian

and Permian formations are si l tstones, sandstones, and conglomerates. The

Mississippi an formations are sandstones and shales. Toward the west carbonate

FIGURE 2

GLACIAL BOUNDARY

1 |

PERMIAN

PENNSYLVANIAN

MISSISSIPPIAN

DEVONIAN

SILURIAN

ORDOVICIAN

BELLEFONTAINE DELAWARE

MISSISSIPPIAN BEREA

OHIO RIVER

1

"CLINTON" SILURIAN

GEOLOGIC MAP OF OHIO

19

becomes a more important component. The Devonian consists of shale grading

into dolomite near the base. The Silurian is nearly all carbonate material,

and the Ordovician consists of interbedded carbonates and shales.

The Sr87/Sr87 ratios have been plotted on a map of Ohio in Figure 3.

It is clear that the high Sr87/Sr86 ratios occur in the east, where the clas­

tic sediments predominate, whereas the low Sr87/Sr86 ratios are found in the

west, especially where the Silurian carbonate rocks are exposed. The rela­

tively high Sr87/Sr86 ratios of water samples from the central and eastern

areas are probably not as high as the Sr87/Sr86 ratios in the Paleozoic shales

found in these areas, but leaching of these shales by the waters certainly

must contribute significantly to the Sr87/Sr86 ratios observed in the waters,

since these ratios are considerably higher than those which would be observed

if the waters had acquired their strontium from carbonate material alone. The

Late Silurian rocks and glacial deposits of western Ohio are known to contain

important amounts of the mineral celestite (strontium sulfate), described by

Feulner and Hubble (1960). Leaching of this mineral by the waters undoubtedly

contributes a major portion of the strontium dissolved in the waters. The

celestite is associated with limestone and with evaporite deposits of gypsum

and rock salt, so that its Sr87/Sr86 ratio was inherited from the Paleozoic

oceans and should therefore be about 0.708.

It is important to note the consistency of the Sr87/Sr86 ratios in

three water samples from Washington County near the eastern Ohio border, each

of which has a different mode of occurrence (Figure 3). Water samples ob­

tained from a stream, from a spring, and from a well all yield Sr87/Sr86 ratios

of 0.7130, which would seem to indicate an isotopically similar provenance for

all waters of this county. Three spring waters from an area in south-central

20

FIGURE 3

MAP OF OHIO SHOWING WATER SAMPLE LOCATIONS,MODE OF OCCURRENCE, AND Sr87/Sr86 RATIOS

W SURFACE WATERS

A SPRING WATERS

• WELL WATERS

^ r EASTIN AND FAURE (1970)

Ohio also y i e l d Sr8 7 /Sr8 6 rat ios which are ind is t inguishable wi th in the l im i t s

of experimental er ror (Figure 3) .

There may be some re la t ionship between the Sr 8 7 /Sr 8 6 rat ios observed

in the water samples and the g lac ia l boundary, since only one of the r e l a t i v e ­

ly high ra t ios occurs to the north of the boundary (Figure 3) . North and west

of the bondary the glaciers pulverized the carbonate bedrock, probably render­

ing i t more susceptible to solut ion by ground waters. In Ashtabula County to

the northeast, where the observed Sr 8 7 /Sr8 6 r a t i o is r e l a t i v e l y h igh, there is

no carbonate bedrock readi ly avai lab le .

The weathering of more radiogenic Precambrian material in the t i l l ,

presumably transported into the state from the north by the g lac ie rs , has had

no apparent e f fec t on the Sr8 7 /Sr8 6 ra t ios o f the water samples.

SUMMARY AND CONCLUSIONS

This study has demonstrated tha t the Sr 8 7 /Sr 8 6 ra t ios in surface and

ground waters throughout the state of Ohio show a s i g n i f i c a n t v a r i a b i l i t y .

Samples were col lected and analyzed in order to provide a wide geographic d i s ­

t r i b u t i o n and a var iety of contacted l i t h o l o g i e s . The measured Sr8 7 /Sr8 6 ra t ios

range from about 0.708 to 0.713, w i th the higher rat ios occurring in eastern

Ohio and the lower ra t ios in the west. We believe that t h i s trend re f lec ts

the change in the dominant l i t ho logy of the Paleozoic sediments across Ohio,

where c l a s t i c sediments predominate in the east and carbonates are more im­

portant in the west.

The study represents the i n i t i a l ) phase o f an attempt to use the Sr 8 7 /Sr 8 6

r a t i o as a t racer of stream and ground water provenance. We feel that the

demonstrated v a r i a b i l i t y of t h i s parameter, and i t s apparent dependence on

22

l i thology in the sampling areas, are suf f ic ient ly encouraging to warrant fur­

ther study of the application of the overall concept. The next phase of the

overall study is to examine the strontium isotopic compositions of water

samples from a single drainage basin within Ohio, which is underlain in d i f ­

ferent areas by carbonate and shale bedrock. We are currently pursuing such a

project in the Scioto River basin, even though further support from OWRR could

not be obtained.

23

REFERENCES CITED

Dasch, E. J . , F. A. H i l l s , and K. K. Turekian, 1966, Strontium isotopes in deep-sea sediments: Science, v. 153, pp. 295-297.

East in, R., and G. Faure, 1970, Seasonal var iat ion of the solute content and the Sr8 7 /Sr8 6 ra t io of the Olentangy and Scioto Rivers at Columbus, Ohio: Ohio J . S c i . , v. 70, pp. 170-179.

Feulner, A. J . , and J . H. Hubble, 1960, Occurrence of stront ium in the surface and ground waters of Champaign County, Ohio: Econ. Geol. , v. 55, pp. 176-186.

Fishman, M, J . , and S. C. Downs, 1966, Methods for analysis of selected metals in water by atomic absorpt ion: U. S. Geol. Survey Water-Supply Paper 1540-C, pp. 42-43.

Hamilton, E. I . , 1965, Applied Geochronology: Academic Press, 267 pp.

Hamilton, E. I . , 1968, The iso top ic composition of stront ium applied to prob­lems of the or ig in of the a lka l ine rocks: Radiometric Dating for Geologists (Hamilton and Farquhar, eds , ) , In tersc ience, pp. 437-465.