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This is to certify that the

thesis entitled

The Geochemistry and Source of Solutes in
Ground Water from the Pennsylvanian Bedrock
Sequence in the Michigan Basin

presented by

Bruce Meissner

has been accepted towards fulfillment
of the requirements for

Masters degree in 690108)’

Major profess

Date 2-16-93

 

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Michigan State
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TO AVOID FINES rotum on or before date due.

DATE DUE DATE DUE DATE DUE

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MSU Is An Affirmative Action/Equal Opportunlty Institution
emana-nd

 

THE GEOCHEMISTRY AND SOURCE FOR SOLUTES IN GROUND WATER
FROM THE PENN SYLVANIAN BEDROCK SEQUENCE IN THE MICHIGAN
BASIN

By

Bruce David Meissner

A THESIS

Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of

MASTER OF SCIENCE

Department of Geological Sciences

1993

ABSTRACT

THE GEOCHEMISTRY AND SOURCE OF SOLUTES FOR GROUND WATER
FROM THE PENNSYLVANIAN BEDROCK SEQUENCE IN THE MICHIGAN
BASIN

By

Bruce David Meissner

Ground water form the Grand River-Saginaw aquifer and Parma-Bayport aquifer
contain dissolved solids concentrations up to 92,000 and 240,000 mg/L, respectively.
Analysis of geochemical data from the Grand River-Saginaw aquifer (550 geochemical
and 150 stable-isotope samples) indicates that (l) the dominant hydrochemical facies in
decreasing areal distribution, are Ca-HCO3, Na-Cl, and Ca-SO4; (2) Na-Cl facies are
present in all units within the Saginaw Bay Area, a regional ground-water-discharge area;
(3) cation ternary diagrams indicate the principle process affecting water chemistry in the
aquifers is mixing of Ca- and Na-rich solutions; (4) isotopic ratios indicate that the water
in the aquifers is meteoric; (5) ratios of selected ions to Br and Cl as well as Carpenter
Function:Cl ratios suggest that the solutes in the aquifers have resulted, in part, from
dilution of a marine derived brine from the Parma-Bayport aquifer. Solute concentrations
of other less concentrated waters in the aquifers (TDS < 750 mg/L) have originated
through rock-water interaction that has occurred in the overlying glacial-drift material
prior to recharge into underlying bedrock aquifers. Brine in the Panna-Bayport aquifer
appears to have been derived through the evapo-concentration of seawater concentrated
to near halite precipitation and enriched in Ca and depleted in 804, Mg, and K with

respect to equivalently evaporated seawater.

ACKNOWLEDGMENT S

I would like to dedicate this thesis to my wife and fellow geologist Jolene
Meissner. Her support throughout this graduate school ordeal was nothing short of
fantastic. I would like to thank my parents for providing continued support and
encouragement throughout my college career and never asking the most aggravating
question a geologist is confi'onted with: ”What the hell are you going to do with
Geology?"

A special thanks to my mentor Tim Flood, his love of geology and genuine
concern and confidence in his students provided the impetus to pursue my own interests in
Geology. I would like to thank my advisor Dave Long for much needed help and many
discussions providing guidance in this work as well as my committee members Duncan
Sibley and Graham Larson. The US Geological Survey-WRD funded this research and
Norm G. Grannemann provided invaluable help and complete support throughout this
work, ”Thank You Norm". Others at the US Geological Survey I would like to thank
include Craig E. Oberst for patiently answering many questions about sampling
procedures, D. B. Westjohn for many critical reviews of my work and helpful discussions,

and other past members of the RASA project.

iii

TABLE OF CONTENTS

LIST OF TABLES ............................................................................................................ vii
LIST OF FIGURES ........................................................................................................... viii
CHAPTER 1: INTRODUCTION
Purpose and Scope .......................................................................................... 1
Approach ........................................................................................................ 6
Geohydrologic Framework .............................................................................. 8
Aquifers .......................................................................................................... 8
Ground Water Flow Directions ........................................................................ 13
Previous Work on the Geochemistry of the System .......................................... 15
Methods of Data Collection and Analysis ........................................................ 18
CHAPTER 2: GEOCHEMICAL DISTRIBUTION MAPS
Introduction .................................................................................................... 26
Dissolved Solids .............................................................................................. 28
Chloride .......................................................................................................... 28
Sulfate ............................................................................................................. 3 1
Hydrochemical Facies and Piper Plots ............................................................. 33
Parma-Bayport Aquifer ................................................................................... 39
Summary ......................................................................................................... 40
CHAPTER 3: GRAPHICAL DATA REDUCTION OF
CHEMICAL DATA
Introduction .................................................................................................... 42
Cl/Br Ratio Analysis ........................................................................................ 43
Interaction with Brine ...................................................................................... 43
Origin of Brine ...................................................................................... 48
Chemical Changes in the Subsurface ..................................................... 52
Carpenter Function Analysis ................................................................. 62
Summary ......................................................................................................... 66
CHAPTER 4: CHEMICAL MODELING
Introduction .................................................................................................... 69
Density Determination .......................................................................... 72
Results and Discussion .................................................................................... 73
Carbonate Minerals ............................................................................... 73
iv

Evaporite Minerals ................................................................................ 76

Alumino-Silicate and Silicate Minerals .................................................. 76
Summary ......................................................................................................... 80
CHAPTER 5: ISOTOPE DATA REDUCTION
Introduction .................................................................................................... 83
Stable Isotopes of Oxygen and Hydrogen ........................................................ 84
Mixing .................................................................................................. 89
Summary .............................................................................................. 93
Stable Isotopes of Sulfur and Carbon ............................................................... 94
Sulfur Isotopes ..................................................................................... 94
Carbon Isotopes .................................................................................... 99
Summary .............................................................................................. 102
CHAPTER 6: SUMMARY AND CONCLUSIONS
Summary ......................................................................................................... 103
Conclusions ..................................................................................................... 106
BIBLIOGRAGHY ............................................................................................................. 108

LIST OF TABLES

Table 1. Methods of measurement and analyzing ground water
at the well site. ................................................................................................ 22

Table 2. Selected thermodynamic data used in WATEQ4F
calculations of mineral saturation index values. ................................................ 71

Figure 1.

Figure 2.

Figure 3.

Figure 4.

Figure 5.

Figure 6.

Figure 7.

Figure 8.

Figure 9.

Figure 10.

Figure 11.

Figure 12.

LIST OF FIGURES

RASA study area bounded by the Marshall Sandstone-
Coldwater Shale contact. Also included is the
Pennsylvanian-Mississippian contact bounding the

study area of this thesis ..................................................

Chart showing the Stratigraphic and hydrogeologic

units of the Lower Peninsula of Michigan. .....................

Contour map showing the altitude of the top of the
shallowest brine-bearing sandstone in the Pennsylvanian

rock sequence. ..............................................................

Geologic map of the Lower Peninsula of Michigan. .......

Map showing simulated pre-development equivalent

fi'eshwater head in the Grand River-Saginaw aquifer. .....

Study area for Wood (1969), Ph. D. dissertation in the

upper Grand River basin. ...............................................

Study area for Long et al., (1986 and 1988).

Geochemistry of ground water in Bay county MI ...........

Study are for Badalamenti (1992) MS. thesis. The
Geochemistry and isotopic chemistry of saline ground
water derived from near-surface deposits of the

Saginaw Lowland, Michigan basin. ................................

Sample locations where chemical analyses are available
for ground water from the Grand River-Saginaw

aquifer ...........................................................................

Sample locations where chemical and isotope analyses
are available for water from the Parma-Bayport aquifer.

Location of Saginaw Bay Area in the Lower Peninsula

of Michigan. ..................................................................

Dissolved-solids distribution in ground water from the

Grand River-Saginaw aquifer. .......................................

.................................. 2

.................................. 3

.................................. 5

.................................. 9

.................................. 14

.................................. 16

.................................. 19

.................................. 20

.................................. 24

.................................. 25

.................................. 27

.................................. 29

Figure 13. Dissolved chloride distribution in ground water from
the Grand River-Saginaw aquifer. .................................................................... 30

Figure 14. Dissolved sulfate distribution in ground water from the
Grand River-Saginaw aquifer. ......................................................................... 32

Figure 15a. Modified Piper plot depicting the classification scheme

for hydrochemical facies .................................................................................. 34
Figure 15b. Piper plot for ground water in the Grand River-

Saginaw aquifer with dissolved-solids concentrations

less than or equal to 750 mg/L ......................................................................... 34

Figure 15c. Piper plot for ground water in the Grand River-

Saginaw aquifer with dissolved-solids concentrations

from 751 to 2,000 mg/L. ................................................................................. 36
Figure 15d. Piper plot for ground water in the Grand River-

Saginaw aquifer with dissolved-solids concentrations

greater than 2,000 mg/L. ................................................................................. 36
Figure 16. Hydrochemical facies distribution for ground water

fi'om the Grand River-Saginaw aquifer. ........................................................... 38
Figure 17a. Frequency histogram of Cl/Br ratios for ground water

sampled from the Grand River-Saginaw aquifer. .............................................. 44
Figure 17b. Frequency histogram of CVBr ratios for ground water

sampled from the Parrna-Bayport aquifer. ........................................................ 44

Figure 18. Interpretation of brine origin from location around
seawater evaporation trajectory. ...................................................................... 47

Figure 19. Cl-Br relations of ground water from the Grand River-
Saginaw (a), Parma-Bayport (b), and Marshall (c)
aquifers and Traverse Group waters (d) with the
evaporation of seawater trajectory. .................................................................. 49

Figure 20a. Na-Cl relations of ground water from the Grand River-

Saginaw aquifer with evaporation of seawater

trajectory ......................................................................................................... 50
Figure 20b. Na-Cl relations of ground water from the Parma-

Bayport aquifer with evaporation of seawater

trajectory ......................................................................................................... 50

Figure 21a. Na-Cl relations of ground water from the Marshall
aquifer with evaporation of seawater trajectory ................................................ 51

Figure 21b.Na-Cl relations of ground water fiom the Traverse

Figure 22.

Figure 23.

Figure 24.

Figure 25.

Figure 26.

Figure 27.

Figure 28.

Figure 29.

Figure 30.

Figure 31.

Group with evaporation of seawater trajectory. ............................................... 51

K-Br relations of ground water from Grand River-
Saginaw, Parma-Bayport, and Marshall aquifers with
evaporation of seawater trajectory. .................................................................. 53

K-Cl relations of ground water from Grand River-
Saginaw, Parma-Bayport, and Marshall aquifers with
evaporation of seawater trajectory. .................................................................. 54

Ca—Br relations of ground water from Grand River-
Saginaw, Parma—Bayport, and Marshall aquifers with
evaporation of seawater trajectory. .................................................................. 55

Ca-Cl relations of ground water from Grand River-
Saginaw, Parma-Bayport, and Marshall aquifers with
evaporation of seawater trajectory. .................................................................. 56

Mg-Br relations of ground water fi'om Grand River-
Saginaw, Parma-Bayport, and Marshall aquifers with
evaporation of seawater trajectory. .................................................................. 57

Mg-Cl relations of ground water from Grand River-
Saginaw, Panna-Bayport, and Marshall aquifers with
evaporation of seawater trajectory. .................................................................. 58

SO4-Br relations of ground water from Grand River-
Saginaw, Panna-Bayport, and Marshall aquifers with

. evaporation of seawater trajectory. .................................................................. 60

SO4-C1 relations of ground water from Grand River-
Saginaw, Parma-Bayport, and Marshall aquifers with
evaporation of seawater trajectory. .................................................................. 61

CF (Carpenter Function)-Br relations of ground water

from Grand River-Saginaw (a), Panna-Bayport (b), and

Marshall aquifers (c) and Traverse Group water (d)

with evaporation of seawater trajectory. .......................................................... 63

CF (Carpenter Function)-Cl relations of ground water

from Grand River-Saginaw (a), Parma-Bayport (b), and

Marshall aquifers (c) and Traverse Group water (d)

with evaporation of seawater trajectory. .......................................................... 65

Figure 32.

Figure 33.

Figure 34.

Figure 35.

Figure 36.

Figure 37.

Figure 38.

Figure 39.

Figure 40.

Figure 41.

Figure 42.

Cl-Br relations with evaporation of seawater trajectory
presenting the location of water masses portrayed on
ionzBr and ionzCl plots. ................................................................................... 68

Frequency histogram for calcite saturation index values
for ground water from the Grand River-Saginaw
aquifer ............................................................................................................. 74

Frequency histogram for aragonite saturation index
values for ground water from the Grand River-Saginaw
aquifer ............................................................................................................. 74

Frequency histogram for dolomite saturation index
values for ground water from the Grand River-Saginaw
aquifer ............................................................................................................. 75

Frequency histogram for halite saturation index values
for ground water fi'om the Grand River-Saginaw
aquifer ............................................................................................................. 77

Frequency histogram for gypsum saturation index
values for ground water from the Grand River-Saginaw
aquifer ............................................................................................................. 78

Frequency histogram for anhydrite saturation index
values for ground water from the Grand River-Saginaw
aquifer ............................................................................................................. 78

Frequency histogram for quartz saturation index values
for ground water fi'om the Grand River-Saginaw
aquifer ............................................................................................................. 79

Frequency histogram for chalcedony saturation index
values for ground water fiom the Grand River-Saginaw
aquifer ............................................................................................................. 79

Mineral stability diagram of sodium alunrinosilicate
minerals ground water from the Grand River-Saginaw
aquifer ............................................................................................................. 81

Mineral stability diagram of potassium aluminosilicate
minerals ground water from the Grand River-Saginaw
aquifer ............................................................................................................. 81

Figure 43.

Figure 44.

Figure 45.

Figure 46.

Figure 47.

Figure 48.

Figure 49.

Oxygen and deuterium relations for ground water fiom
the Grand River-Saginaw and Parma-Bayport aquifers. ................................... 85

5180 distribution in ground water from the Grand
River-Saginaw aquifer. .................................................................................... 88

5180 versus Cl for ground water from the Grand
River-Saginaw aquifer and Parma-Bayport aquifers. ........................................ 90

8180 versus Cl for ground water from the Glacial-drift,
Grand River-Saginaw, Parma-Bayport, and Marshall

aquifers. .......................................................................................................... 91
Frequency histogram for 834s in dissolved sulfates for

ground water from the Grand River-Saginaw aquifer. ...................................... 96
834s versus S04 for ground water from the Grand

River-Saginaw aquifer. .................................................................................... 98

Frequency histogram of 813C for ground water fi'om
the Grand River-Saginaw aquifer. .................................................................... 101

CHAPTER 1: INTRODUCTION
PURPOSE AND SCOPE

The purpose of this thesis is to describe the geochemistry and source for solutes in
ground water fi'om the Pennsylvanian and a portion of the Mississippian bedrock sequence
in the Michigan basin. The principle aquifers being studied include the Pennsylvanian age
Grand River-Saginaw and Pennsylvanian-Mississippian age Panna-Bayport aquifers
(referred to collectively in this thesis as the Pennsylvanian aquifers). This thesis
encompasses two of four aquifers presently being studied in the US. Geological Survey-
Water Resource Division, Michigan Regional Aquifers System Analysis (RASA) project.
The RASA study area is bounded by the contact between the Coldwater Shale and the
Marshall Sandstone, and the study area for this thesis is defined by the Pennsylvanian-
Mississippian contact in the Michigan basin. Figure 1 displays the RASA study area as
well as the study area for this thesis. The goal of the RASA project is to study the
geology, geochemistry, and the hydrology of aquifers in Mississippian and younger units in
the central part of the Lower Peninsula of Michigan. The aquifers studied in the RASA
project include the Mississippian age Marshall aquifer, the Parma-Bayport and Grand
River-Saginaw aquifers as well as Quaternary age Glacial-Drift aquifers (Figure 2).

Presently water ranging from fresh to brine exists in near surface bedrock aquifers
(Mississippian and younger) in the Michigan basin. Brine in the Mississippian-age
Marshall sandstone has been related to evapo-concentrated seawater (Long et al., 1993;
Meissner et al., 1992).

Water in the Pennsylvanian aquifers shows a variety of concentrations ranging from
fresh water to brine. Ground water data indicates fi'esh water and saline water exist in the
Grand River-Saginaw aquifer and water ranging fi'om fresh to brine is present in the

Parma-Bayport aquifer. Brine and saline ground water in the Pennsylvanian aquifers have

 

 

  
 

  
  

 

 

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Figure 2. Stratigraphic column and hydrogeologic units in the study
area (Modified from Mandle and Westjohn, 1989;
stratigraphic column modified from Michigan Geological
Survey, 1964, Chart 1).

been documented by several investigators, Houghton (1838), Winchell (1861), Lane

( 1899), Cooper (1905), Leverett and others, (1906), Cook (1913), Twenter (1966),
Western Michigan University (1981) Long et al., (1988), Westjohn (1989), Mandle and
Westjohn, (1989), and Meissner et al., (1992).

Recently Westjohn, (1989) delineated the existence of brine in the Pennsylvanian strata
through the application and interpretation of electric (resistivity) and porosity logs.
Westjohn (1989) defined the top of the shallowest brine-bearing sandstone in the
Pennsylvanian bedrock sequence, and this distribution of brine is shown on Figure 3.
Brine in the Pennsylvanian units exists where in direct contact with the Michigan
Formation, along the perimeter of the contoured area. In the center of the basin
Pennsylvanian units contain brine as much as 150 meters above the Michigan Formation
(W estjohn, 1989). The Panna Sandstone is the shallowest brine reservoir in the basin with
brine found at distances as small as 10 miles down regional dip from areas containing
freshwater (Westjohn personal commun, 1992). The Parma Sandstone does contain fiesh
water where it subcrops and is in direct contact with the glacial drift.

The impact of geologic control on the distribution of brine in the Pennsylvanian
aquifers is an important issue to present and must be considered when making basin wide
interpretations of the controls on ground water chemistry and origin of brine conclusions.
In general, the Pennsylvanian rock sequence is brine bearing where it is confined and
isolated, such as when it is capped by shale or where it is overlain by Jurassic deposits
(Westjohn, personal commun, 1992). The extent of brine and saline water in the
Pennsylvanian aquifers is extensive and unfortunately few chemical analyses are available
for the more concentrated waters in the aquifers, however enough data is available to
provide a general evaluation of the geochemistry.

Wilson and Long, (1986 and 1993) found Michigan basin Devonian and Ordovician
formation brines to have originated from the evaporation of seawater. Brine in the

Mississippian age Marshall Sandstone has been to be geochemically and isotopically

86° 85° 84° EXPLANATION

ALTITUDE OF SHALLOWEST
BRIE-BEARD“! SANOSTONE

 
  
 
 
   

      
   
  
    
  

- > 300
38%. 300 to 100
CONTACT OF MARSHALL 3:333: 100 to -100
45‘— + sweeten: +
[ meowwaren some 5— <-1oo
feet above eee level
PENNSYLVANIAN. ' d’i" 3'”
re
44’-

   

1- IMIT OF ERIN
PENNSYLVANI
BANDSTONEO

 
   

43°—

42°—

 

0 10 25 50 100 MlLES
l 1 1 1 l

 

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0 20 50 100 KILOMETERS

Figure 3. Contour map showing the altitude of the top of the shallowest brine-bearing
sandstone in the Pennsylvanian rock sequence (Modified from Westjohn,

1989, figure 18).

similar to the Devonian brine (Meissner et al., 1992). One of the hypotheses for this thesis
is that brine in the Pennsylvanian/Mississippian age Parma-Bayport aquifer is similar to the
Marshall and Devonian brines. In this study the Parrna-Bayport brine chemistry is
compared to the chemistry of brine from the Marshall Sandstone and Devonian-aged
Traverse Group to make interpretations on the origin and evolution of the Parma-Bayport
brine. The understanding of the concentrated waters in the Parma-Bayport aquifer may
lend insight into the source of concentrated fluids present in the Grand River-Saginaw
aquifer. The Parma-Bayport brine is compared to ground water from the Grand River-
Saginaw aquifer to investigate the hypothesis that brine, possibly the Parma-Bayport brine,
is the source of solutes for many waters in the Grand River-Saginaw aquifer. The
existence of a relationship between brine in the Michigan basin and the chemistry of waters
in the Grand River-Saginaw aquifer may have implications on regional ground water flow

in the basin.

APPROACH

The origin and evolution of waters in sedimentary basins has been the focus of many
studies in recent years (Clayton et al., 1966; Graf et al., 1966; Hitchon, 1969, 1971;
Nesbitt, 1985; Wilson and Long, 1986 and 1993; Egeberg and Aagaard, 1989; Wilson,
1989). Within these studies chemical and isotopic data from groundwater samples were
used to determine the main processes controlling the chemistry of the water. Analysis of
chemical and isotope data for waters in sedimentary basins commonly deals with the
question: how has this particular body of water evolved through time? The methodology
used in answering this question entails separating the water samples into two phases, the
solvent and the solutes. The solvent is the water molecule itself whereas the solutes are
the dissolved chemical species in the ground water sample. The source of the solvent and

the solutes in a water mass can be independently identified through data reduction

techniques involving chemical and isotope data from the aquifer. The isotope data,
particularly the stable isotopes of oxygen and hydrogen, are used to determine the source
of the water molecules in the system, identify water masses and interpret mixing relations
among various water masses (Long et al., 1986). The chemical data is used to evaluate
the source of the solutes relating their source to be the result of rock-water interaction,
mixing of water masses or brine evolution processes (Carpenter, 1978; Bath and
Edmunds, 1981; Land, 1987; Long et al., 1988; Egeberg and Aagaard, 1989; Banner et
al., 1989; Steuber and Walter, 1991).

Major processes afi‘ecting groundwater chemistry include concentrating and modifying
processes (Wilson, 1989). Concentrating processes include evaporation, evaporite
dissolution, and shale membrane filtration (Hitchon, 1969). Modifying processes include
the alteration of water chemistry through rock - water interaction, biologic activity, and
through the mixing of water masses of different composition (Wilson, 1989). Early
studies in geochemistry of natural ground waters dealt with geochemical processes as
being the only control on the composition and concentration of ground water (Domenico
and Schwartz, 1990). However, mass transport processes, particularly mixing often play a
major role in controlling ground water chemistry (Hitchon et al., 1969; Desauliniers et al.,
1981; Siege] and Mandle, 1984; Long et al., 1988). Frape et al., (1984) states that the
unraveling of the geochemical evolution of ground water with different chemistries in a
given rock mass involves addressing geochemical reactions and/or mixing. The role of
advection and dispersion on solute concentrations and stable isotope values is important to
consider as a control on ground water chemistry in Michigan basin sediments.

The impact of geological change in the Michigan basin must have had a great impact
on ground water chemistry evidenced presently by the existence of many different water
masses with different chemistries within the basin's aquifers (Twenter, 1966; Western
Michigan University, 1981; Long et al., 1988; Westjohn, 1989). Changes related to

depositional episodes, structural processes (uplifi and defamation) as well as periods of

glaciation may have had an impact on ground water chemistry. Potential changes could
result from the displacement of water from aquifers through uplifi or compaction, the
emplacement of water whether from present day recharge to the aquifers or from water
emplaced that is associated with the deposition of marine sediments. Difficulty arises in
deciphering the impact and magnitude that various geologic events could have had on
ground water chemistry. The geologic history of the Michigan basin with past
emplacement and displacement of water combined with present day regional hydrology
develops a complex origin and evolution of ground water presently occupying the
aquifers.

GEOHYDROLOGIC FRAMEWORK

The Michigan basin is a nearly circular basin in which an extensive accumulation of
sedimentary rocks underlies the Lower Peninsula of Michigan, parts of Michigan's Upper
Peninsula, Illinois, Ohio, Indiana, Wisconsin, and Ontario, Canada (Figure 4).

Sedimentary rock, which ranges in age from Precambrian through Jurassic, exceeds
17,500 ft. in thickness near the center of the basin and overlies Precambrian crystalline
rocks (Lillienthal, 1978). The sedimentary rocks are mantled by glacial deposits, the result

of glaciation during late Wisconsinan time (Mandle and Westjohn, 1988).

AQUIFERS

There are four major aquifers of concern in the fiamework of this thesis, a Glacial-drift
aquifer and three bedrock aquifers separated by confining units (Figure 2). The bedrock
aquifers, in ascending order, are the Marshall, Parma-Bayport, and Grand River-Saginaw
aquifers. The Coldwater shale that ranges fi'om 500 to 1,100 ft in thickness, forms the
base of the aquifer system. This thesis concentrates on the Grand River-Saginaw and

Parma-Bayport aquifers, however chemistry of waters in the overlying Glacial Drift

84° 312°
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0 60 100 MILES

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EXPLANATION
DESCRIPTION OF MAP UNITS

Upper Jurassic rocks

[:2] Pennsylvanian Grand
River Formation

[3 Penneylvanian Saginaw
Formation (includes Parma
Sandstone Member

a Mieaiaalppian Bayport
Limestone and Michigan
Formation

Mieeiaalopian Marshall
B Sandstone

Mississippian Coldwater and Sunbury
Shalea

%

Mississippian and Devonian Berea.
Sandstone. Bediord and Ellaworth
Shalea

Devonian Miaalesippian and Antrlm
Shale

Devonian rocke,undiiterentiated

Figure 4. Geologic map of the Lower Peninsula of Michigan (Modified from HM

Martin, 1955, fig. 11).

10

aquifer and especially the underlying Marshall aquifer is important to the discussion in the
thesis and therefore is referred to in comparison of chemical similarities and difi‘erences.

The Marshall aquifer is the basal aquifer in the RASA study area. It includes
sandstones that overlie the Coldwater confining unit as well as sandstones that form the
lower part of the Michigan Formation (Fig. 2). The Marshall aquifer consists of two or
more permeable sandstones in the central part of the basin, but, toward the subcrop
regions, the aquifer consists of one permeable sandstone. In areas where more than one
sandstone is present, intercalated carbonate, shale, siltstone, and/or evaporite separate
permeable sandstones. The composite thickness of permeable sandstone ranges from
approximately 75 to 225 ft (D.B. Westjohn, personal commun, 1992). Separating the
Marshall and overlying bedrock aquifer is the Michigan confining unit.

The Michigan confining unit is an intercalated sequence of thin bedded limestone,
dolomite, shale, gypsum, anhydrite, and lenses of sandstone. The unit ranges from 100 it
in thickness near the fiinges of the subcrop area to about 400 ft over the central part of the
study area. (DB. Westjohn, personal commun, 1992).

Cohee (1965) reports that the Bayport Limestone overlies the Michigan Formation and
consists of limestone, cherty or sandy limestone, as well as intercalated sandstone and
limestone. The Bayport Limestone is thin or absent in the central part of the basin. In
areas where the Bayport is absent the Parrna Sandstone is present and overlies the
Michigan confining unit. Recent geophysical studies indicate that the Bayport consists
predominantly of permeable limestone and sandstone (D.B., Westjohn, written
communication, 1991). The Parma Sandstone and Bayport Limestone are combined to
form the Parrna-Bayport aquifer because they form a hydraulically connected and
stratigraphically continuous permeable unit over most of the basin. The thickness of the
Parma-Bayport aquifer ranges fi'om 75 to 150 fi. Over most of the study area, the aquifer

is overlain by shale that comprises the Saginaw confining unit.

11

Overlying the Saginaw confining unit is the Grand River-Saginaw aquifer.
Pennsylvanian rocks have been subdivided into the Saginaw (Early Pennsylvanian) and
Grand River Formations (Late Pennsylvanian). The stratigraphic column published by the
State (Michigan Department of Conservation, 1964) shows the Grand River and Saginaw
F orrnations separated by a major erosional unconformity. This interpretation is based
primarily on the work of Kelly (193 6), who suggested rock units exposed near Grand
Ledge, Michigan, are younger than the Saginaw Formation. Kelly (193 6) noted the
presence of a basal conglomerate associated with proposed younger Pennsylvanian rocks,
and suggested the name Grand River Group. The nomenclature proposed by Kelly (193 6)
was modified slightly in the stratigraphic column published for the State, but rather than
indicate ”Group” status, this stratigraphic column assigns rocks suggested to be Late
Pennsylvanian to the Grand River Formation. The bedrock geological map recently
published by the State (Milstein, 1937) shows a 350 mi2 area where glacial deposits are
underlain by the Grand River Formation, and delineation of the formation is based entirely
on nomenclature recorded on geological logs of hydrocarbon exploration boreholes, or
holes drilled for water wells. There are no known stratigraphic horizons of regional extent
that separate Grand River and Saginaw Formations, and in general it is not possible to
assign forrnational nomenclature based on geological descriptions. Pennsylvanian
sandstones are stratigraphically discontinuous, only locally constitute the dominant
lithology, with shale, siltstone, limestone, and coal as minor contributors to the total
thickness of the Pennsylvanian rock sequence. For purposes of characterizing the
hydrogeological framework of the Michigan basin aquifer system, the composite thickness
of the Pennsylvanian sandstones is grouped to form the Grand River-Saginaw aquifer
(D.B. Westjohn, personal commun, 1992). The Grand River-Saginaw aquifer is
considered as a single layer for modeling purposes. The composite thickness of
sandstones ranges from 300 to 400 it in the east-central part of the basin, where

Pennsylvanian rocks are the thickest (600 to 700 ft). However, over most of the basin the

12

composite thickness of the sandstones that comprise the Grand River-Saginaw aquifer is
less than 200 fi (D.B. Westjohn, personal commun, 1992).

Transmissivity values for 47 aquifer tests performed on the Grand River-Saginaw
aquifer range from 975 to 43,333 fiz/d. Horizontal hydraulic conductivity is estimated to
range fi'om 1 to 100 RM (V anlier et. al., 1973; Michigan Department of Public Health,
Engineering Division, written communication, 1987; Michigan Department of Natural
Resources, Geological Survey Division, written communication, 1987).

Mineralogic information on aquifer matrix is limited as unfortunately little literature on
the geology of the Pennsylvanian bedrock sequence in Michigan exists (Figure 2). The
Saginaw Formation sands are predominantly fine grained litharenites. The aquifer is
generally not cemented but does contain small amounts of quartz and calcium-carbonate
cement (Wood, 1969). Preliminary solid-phase data from the RASA project indicates that
the sandstone aquifer that now contains freshwater may have previously contained brine
(Kramer and Westjohn, 1993). Also the mineral paragenetic sequence and carbonate
phases are similar in Pennsylvanian and Mississippian sandstones and isotopic
compositions of authegenic mineral phases have the same range of values in Pennsylvanian
and Mississippian sandstones (Kramer and Westjohn, 1993). The solid phase work
suggests that basin wide evolution of brine resulted in a suite of authegenic mineral phases

common to all Carboniferous sandstones (Kramer and Westjohn, 1993).

EI‘I‘TTLJ

During the Mesozoic and early Cenozoic an eroded bedrock surface developed.
Sediments accumulated briefly during the Late Jurassic and Late Cenozoic Eras. Red
Beds of Jurassic age overlie the Grand River and Saginaw Formations in the west-central
part of the study area. The red beds are composed of red mud, poorly consolidated red
shale, gypsum, and minor amounts of sandstone. The red beds together with the fine-
grained glacial deposits form the subregional glacial till-red beds confining layer (Mandle
and Westjohn, 1989).

13

The Glacial-drift aquifer is composed of deposits ranging from fine-grained lacustrine
clay, glacial till, and glaciofluvial deposits (Mandle and Westjohn, 1989). Glacial deposits
range from 10 to 1000 feet thick throughout Michigan (Western Michigan University,
1981). Where coarse-texture deposits predominate, as in the northern and northwestern
parts of the study area, they are productive aquifers. In low-lying areas, such as the
Saginaw Lowland area where proglacial lake beds predominate, the Quaternary deposits
are a confining unit for more permeable, underlying unconsolidated deposits and
sedimentary rock. None of these deposits is regionally continuous; they are aquifers or
confining units in relatively small areas. The alluvium and outwash, or other coarse-

grained Quaternary deposits are grouped to form the Glacial-Drift aquifer.

GROUND-WATER FLOW DIRECTIONS

Physical flow information for the Pennsylvanian aquifers is not available, however
regional hydrology is proposed. Preliminary computer simulations of freshwater head
distributions for the Grand River-Saginaw aquifer indicate that ground water flows fi'om
the upland areas toward the regional discharge area in and around the Saginaw Bay Area
(Figure 5) (Mandle and Westjohn, 1989; G. Barton, personal commun, 1993).
Vugrinovich, (1986) noted a similar distribution in hydraulic heads, which were not
corrected for reference density. Vugrinovich concluded that hydraulic head in the
Marshall and Grand River-Saginaw aquifers were generally in equilibrium with present-
day land-surface elevations. Larson (1979) found tritium concentrations in the Tri-county
region that indicated direct recharge to the Saginaw Formation and therefore to the Grand
River-Saginaw aquifer is taking place. Ground-water flow information available for the
southern portion of the study area indicates that the flow of the area is controlled by the
local surface topography and not by movement in other formations (Wood, 1976;
VanLier, et al., 1973).

 

 

 

03'
44
‘3'
42‘
1
Sue Irom US. Geological
SUVOY 12500.000 "1.9 (I) 510 190 MLES
r i f
O 50 100 KLOMETERS
EXPLANATION

—000— LNE or EQUAL HYDRAULIC HEAD
CORRECTED To FRESHWATER
DENSITY (1.94 shes/ft? at 60°F)

LIE OF CONTACT BETWEEN SAGNAW

FORMATDN AND BAYPORT LNESTOI‘E
(From HM. Man'l'l. 1955)

Figure 5. Map showing simulated pre-development equivalent freshwater head in the
Grand River-Saginaw aquifer (Mandle and Westjohn, 1989, fig. 9).

15

PREVIOUS STUDIES ON GEOCHEMISTRY OF THE SYSTEM

The only work done on the geochemistry of ground water in the Pennsylvanian
aquifers has focused on the Grand River-Saginaw aquifer (Wood, 1969, and 1976;
VanLier et al., 1973; Slayton, 1982; Long et al., 1986, and 1988; Badalamenti, 1992).
Previous studies performed on the geochemistry of the Grand River-Saginaw aquifer have
focused on portions of the aquifer, no basin wide study has been done. Two main areas of
the aquifer have been studied, the southern part (Wood, 1969, and 1976; VanLier et al.,
1973; Slayton, 1982) and the central part, specifically near Saginaw Bay (Long et al.,
1986, and 1988; Badalamenti, 1992).

Wood (1969), studied the distribution, source and mineral equilibria of major chemical
constituents in ground water from the Saginaw Formation within the context of the
geology and flow system of the aquifer in the Upper Grand River-Basin, Michigan (Figure
6). The main source of solutes is from rock-water interactions in the overlying glacial
drift, which is hydraulically connected with the Saginaw Formation. Mixing with lower
formations in the southern part the Pennsylvanian subcrop area is limited as the underlying
Bayport limestone is allowing only small amounts of water to pass into the overlying
aquifer. Leaching experiments on soil-glacial material and Saginaw Formation sandstone
to determine source of dissolved-solids supported this interpretation. Water obtained
fiom leaching the glacial material was found to be very similar to water found in the
Glacial-Drifi and Grand River-Saginaw aquifers. Leaching experiments also indicated that
the sandstones from the Saginaw Formation yield very small amounts of dissolved solids.

Wood (1976) summarized five features that are of importance in the evaluation of
water quality of the southern part of the Grand River-Saginaw aquifer system: i) There
was considerable variation in the concentration of several chemical parameters over very
short horizontal distances, 2) Water quality does not appear to be related to the depth of

the well, 3) Water in wells in the overlying glacial material yielded water of poorer quality

16

85'

 

Study area

Wanna?

 

 

 

42° 30'

 

kilometers

Figure 6. Study area for Wood (1969) Ph.D disautation in the upper Grand River

17

than water from wells completed in the Saginaw Formation, 4) Water quality in some
wells completed in the Saginaw Formation experienced a sudden deterioration, although
the wells had yielded water of good quality for many years, and 5) Base flow of
unpolluted streams appears to contain more dissolved-solids than water from wells in the
Saginaw Formation (Wood, 1976). These five features of the Saginaw Formation led to
Wood (1976) to present a model for ion filtration (reverse osmosis) impacting water
chemistry of the aquifer. Wood's model for ion filtration described two types of water
found in the Saginaw F orrnation. The first type of water derived its dissolved-solids from
dissolution of minerals in the overlying glacial drifi and moved along flow path into the
Saginaw Formation, the chemistry of this water type is identical to that found in the
overlying glacial drifi material. The second type of water also derived its dissolved solids
fi'om the overlying glacial drift, however the flow line for this water intersected a clay or
shale bed with membrane properties. This water while passing through the filter will have
the dissolved solids concentrations reduced creating anomalous water chemistry observed
relative to water above in the drift.

Slayton (1982) revisited the work of Wood (1969 and 1976) and performed a study
investigating field evidence for shale membrane filtration (reverse osmosis) of ground
water primarily in areas of Eaton and Ingham counties. In this study Slayton found that in
areas of the Saginaw Formation where shale is present shale membrane filtration is a
process that controls groundwater geochemistry. Water samples in areas of the Saginaw
Formation had dissolved-solids concentrations greater than those found in the overlying
drifi. Slayton provided two explanations for the dissolved-solids distributions 1) direct
recharge to the Saginaw F orrnation in areas supported by high tritium concentrations
(Larson, 1979) and 2) areas where shale is present in the Saginaw Formation low tritium
concentrations prevail and are believed to be impacted by shale-membrane filtration.
Slayton concluded that shale membrane filtration and direct recharge were occurring

within the study area.

18

Long et al., (1986 and 1988) studied 100 ground water samples fi'om the Grand River-
Saginaw aquifer in Bay county MI (Figure 7). The chemical and isotope database
generated was used to determine the chemical controls on ground water in selected
townships in Bay county. Saline water was found in the Grand River-Saginaw aquifer and
was attributed to upward advection or diffusion of brine. Isotopically light meteoric water
was found in the study area and was attributed to ground water recharge to the aquifer
when the climate was cooler, such as during recent glaciation. Sulfate reduction was
shown to be occurring in the aquifer afl‘ecting 804 and HCO3 concentrations as well as 8
34S and 513C values.

Badalamenti, (1992) studied 55 samples from the Grand River-Saginaw aquifer within
the Saginaw Lowland incorporating the study area of Long et al., (1986) (Figure 8). She
found that the Saginaw Lowland Area was a transition zone between 1) modern meteoric
water and brine compositions and 2) the occurrence or lack of sulfate reduction in the
system. She concluded that the regional ground water system is influenced by meteoric
water and brine end-members. The brine end-member is most dominant in Bay county.

The work of Long et al., (1986 and 1988) and Badalementi 1992) indicate the mixing
of brine and meteoric water as a source for chemical trends observed in the Saginaw Bay
Area and east-central part of the basin. With additional data from the Grand River-
Saginaw and especially data from the Parma-Bayport brine and deeper formations the
relationship between brine and less concentrated water in the overlying aquifers can be

better analyzed.

METHODS OF DATA COLLECTION AND ANALYSIS

Ground-water sample locations for the Michigan RASA project were selected based on

well location, depth, open interval, pumping equipment, aquifer type, and lithology
(Dannemiller, 1990). The majority of the samples were taken from municipal and

 

BAY COUNTY I

 

    

 

 

«4e

0 4O 80
KILOMETERS

Figure 7. Study area for Long et al., (1986, 1988) Geochemistry of ground waters in
Bay county MI. (modified from Long et al., 1986, fig. 1.1)

20

MICHIGAN BASIN STUDY AREA

 
  
 
  

AHENAC
GLADWIN

MIDLAND "V

 

 

 

 

 

I ma Ina-c I TUSCOLA
‘” ”- GHANOT SAGINAW
Scale
I I. * l
25 ha
N

Figure 8. Study area for Badalameni (1992) MS. thesis The Geochemistry and
isotopic chemistry of saline ground water derived from near-surface deposits
of the Saginaw Lowland, Michigan basin (Modified from Badalamenti, 1992,
fig. 1.2).

21

domestic wells from which drillers logs were available. The samples were collected from
the wells once sufficient pumping yielded constant temperature and specific conductance.
Analysis of the samples included measurements of parameters used for geochemical
modeling. At each well site samples were taken and were field tested for specific
conductance, pH, and temperature, also on-site concentrations of dissolved oxygen,
alkalinity as CaCO3, sulfide as S, total iron, and ferrous iron were determined on the
majority of samples, see Table 1 for the methods used in the determination of these
concentrations.

Further analysis of the samples included lab analysis for dissolved organic carbon
(DOC), sulfate, sulfide, Mn, Mg, Fe, total dissolved solids as Residue on evaporation
(ROE), Sr, Br, Al, Li, Ca, Na, K, Cl, B, As, Zn, and F. Stable isotope analysis was
performed on many samples also. Isotopic ratios of 18O/16O, 2H/IH, 34S/328, and
13C/12C were measured along with percent 14C and Tritium (3H) analysis on selected
samples. In preparation for chemical analysis of the water samples they were filtered
through a membrane with a pore size of .45 um (micrometer). During this process the
water filtered was supplied through a continuous flow line to minimize exposure of the
sample to the atmosphere. The water samples were preserved according to methods
described in Brown and others (1970) and Skougstad and others (1978), (Dannemiller
and Baltusis, 1990). The samples were then analyzed by the US. Geological Survey
National Water Quality Laboratory in Arvada, Co.

This thesis encompasses all above study areas, and a database that includes 550
chemical and 150 isotopic (O and D) analyses. Thirty-one chemical and isotopic analyses
have been derived fiom Long et al., (1986) and 240 chemical analyses from Wood (1969).
This thesis also adds 165 chemical and isotopic analyses fiom RASA sampling efi‘orts
(Dannemiller and Baltusis, 1990), 106 chemical analyses fi'om the Department of Health
(Mark Breithart, 1992), 20 chemical analyses from the USGS WATSTORE database
(1974-1987), 6 chemical analyses fiom the Department of Natural Resources

22

Table 1: Methods of measuring and analyzing ground water at well site (modified fi'om

Dannemiller and Baltusis, 1990).

Property of
QM

Temperature, in
degrees Celsius

Specific
conductance in
microsiemens at
25° Celsius.

l" l' 'ty
(bicarbonate) in
milligrams per
liter

Dissolved
oxygen in
milligrams per
liter

Ferrous iron,
(Fc2+) in
micrograms per
liter

Total iron

(Fe), in
micrograms per
liter

Sulfide (52-), in
milligrams per liter

W

Recorded during specific-conductance measurement by use of
thermistor in specific-conductance probe. Probe calibrated
with a certified mercury thermometer (Wood, 1976, p. 10).

Specific-conductance meter calibrated with standards obtained
from U.S.G.S. National Water Quality Laboratory. Results were
temperature corrected by use of the following correction

factor, where temperature (T) is measured in degrees Celsius:

correction factor = l / l + [0.2(T-25)]

pH meter calibrated with two standard solutions (pH 4.00 and
7.00). Sample water kept at its original temperature during
measurement by means of a water bath.

Potentiometric titration with 0.0163 9N H2804 through end
inflection points. Centroid of the inflection point was
graphically determined (Stumm and Morgan, 1981). Sample
water kept at original temperature with water bath.

Azide modification of Winkler method used (Hach Chemical
Co., 1987). Sample kept from exposure to atmosphere during
collection. The sample bottle was filled in oxygen free
atmosphere.

1, 10 phenanthroline method used (Hach Chemical Co., 1987).
Sample was prevented from exposure to the atmosphere during
sampling.

Ferrozine method used (Hach Chemical Co., 1987)

Methylene blue method used (Hach Chemical Co., 1987).
Sample kept isolated from atmosphere during sampling.

23

(written commun, 1987) and 10 isotope analyses sampled summer 1991, (unpublished
data, USGS WATSTORE database). Figure 9 shows the study area and distribution of
sample locations where chemical analyses are available for the Grand River-Saginaw
aquifer. The majority of chemical and isotope data for the Grand River-Saginaw aquifer
exists in the area outside the brine bearing region defined by Westjohn, (1989). No
chemical or isotope data exists in the northwest part of the aquifer due to thick glacial
deposits that serve as the regions major source of ground water (Baltusis, 1992). Data for
the Farina-Bayport includes 5 chemical and 6 isotope samples from the RASA database, 1
chemical analysis from Wood, (1969) and 5 chemical analyses fiom the Department of
Natural Resources (written commun, 1987). Figure 10 shows the study area of Parma-
Bayport aquifer and displays sample locations with chemical and isotopic analyses

available.

24

 

 

rs + +

 

 

 

 

 

 

“ n +
.L.
43 ‘
’
I
42 + + i: +
A - A _‘ 7
r T V I I I I '
r‘l—TT—T‘TT

Figure 9. Sample locations where chemical analyses are available for ground water
from the Grand River-Saginaw aquifer.

25

45 PENNSYLVANIAN-
; MISISSIPPIAN CONTACT

 

 

 

 

o chemicaldataonly
42 _ * isotopedmonly

 

 

 

 

W—l—I—l—l
1° °. .'°. 1'. .9. .* ’° "" BaaefiumU.S.Geobgieal
wowmnowh“ Surveyl:5(X),(XX)map

Figurelo. Sunplcbcafiomwherechcnfiealanalyaeaareavailable
forgrumdmfimtheParma-Bayportaquifer.

CHAPTER 2: GEOCHEMICAL DISTRIBUTION MAPS

INTRODUCTION

The following maps and discussion describe the areal variations of chemical properties
of ground water fiom Grand River-Saginaw and Farina-Bayport aquifers. Maps of
dissolved solids, dissolved chloride, dissolved sulfate and hydrochemical facies are
discussed. The purpose of these maps is to provide a general distribution and discussion
of patterns of parameters chosen. Constituents used for map preparation were chosen
based on importance in describing chemical properties and trends of ground water in the
aquifer. Dissolved-solids and dissolved chloride were chosen as the encroachment of
saline water in the basin is a concern in some parts of the aquifer specifically in the
Saginaw Bay Area. For the purposes of this thesis the Saginaw Bay Area is defined as the
east-central portion of the Michigan basin bounded by the outermost moraine of the Port
Huron Morainic system (Figure 11). Dissolved sulfate is depicted to investigate the
potential impact of gypsum dissolution in Jurassic deposits and the efi‘ect on water
chemistry (Cohee et al., 1951) as well as the impact of sulfate reduction in the Saginaw
Bay Area (Long et al., 1988). Hydrochemical facies are used as a common tool of
classifying the water chemistry of the aquifer and portrayal of regions of the aquifer with
similar chemical characteristics. Data used in the preparation of the maps was derived
from a variety of well depths and therefore represent general distribution patterns only.
Although databases used to compile these maps provide sufficient data to prepare maps
for the Grand River-Saginaw aquifer, insufficient data are available for ground water in the
Parma-Bayport aquifer. However, general statements about dissolved solids, dissolved
chloride, dissolved sulfate and hydrochemical facies are made and can be found at the end

of this section.

26

27

 

I—J—l—J—I—l—l
to o 10 no so a so" BasefromU.S.Geologieal
reclamation“- vacylzsoomom

Figmo ll. LocafimofflreSaginawBayAreaModifiodfiomWayneand
Zunberge,1965).

28

DISSOLVED SOLIDS

A map of dissolved-solids concentrations was prepared for water from the Grand
River-Saginaw aquifer (Figure 12). The concentrations were determined by summing the
major cation and anion species from analysis of each sample. Dissolved-solids
concentrations range from 41 to 92,352 mg/L within the aquifer with a geometric mean of
832 mg/L. In the southern part of the aquifer and around much of the fiinge area, where
data has been collected, dissolved-solids concentrations are generally less than 1,000 mg/L
and suitable for human consumption, with most of the water sampled containing dissolved
solids concentrations less than 750 mg/L. Water from the east-central part of the aquifer
and part of the Saginaw Bay Area commonly contains dissolved-solids concentrations that
exceed 1,000 mg/L and, locally, exceed 10,000 mg/L. An increase in dissolved-solids
concentrations is noted from the southern part of the aquifer to the Saginaw Bay Area.
The sources of dissolved solids may be due to the addition of solutes through water-rock
interaction (Hem, 1989), through the mixing of meteoric water and brine from the Parma-
Bayport aquifer and from water derived from the overlying Glacial-Drift aquifer in the
southern part of the aquifer. Dissolved solids concentrations in the Glacial drift aquifer
mimic the concentrations in the Grand River-Saginaw aquifer in the southern and
southeast edge of the aquifer. These concentration trends in recharge areas of the aquifer
may indicate solutes derived in the Glacial drifi aquifer as the source of solutes in recharge
areas of the Grand River-Saginaw aquifer. No trend of increasing dissolved-solids

concentrations with depth is noted in the southern part of the aquifer.

DISSOLVED CHLORIDE

Dissolved chloride concentrations in water fiom the Grand River-Saginaw aquifer

are shown on Figure 13. Chloride concentrations vary from 0.7 to 55,000 mg/L with a

29

 

<500mg/L
[:1 >500to<1,000
m >1,000to<5,000
- >5,000mg/L

O >10,000mg/L

 

 

 

 

 

 

 

 

 

 

 

 

linkx

 

 

 

 

 

 

Pennsylvanian-Mississippian

 

 

Contact
W
I—I—Iu—L—I—I—F
lo 0 lo :1 so a) a)" BucfiunU.S.Geological
loolomaoaomh“ M125“),Wmlp

Figure 12. Diasolved-eolidacouoedrationdistrilarficnmapforgmmdwater

30

    
  
   

.. <10mg/L\X
[:3 >10to < 100

m >100to< 1,0001118/L
- >1,000m8IL
O

   

 

  

 

 

 

“—
43
“my; “' ..
42 — Contact
I—l—J—l—I_H
re a lo a) an o a!" “MU'S'WGJ
100103304050“.- Surveylzfimflnnnp

W13, Dissolvedchloridemomafiondiwihm ' mfaflmwm
masonoaRIvor-s-simw-afifer-

31

geometric mean of 28.5 mg/L. Water from about the southern one third of the aquifer has
a chloride concentration of less than 10 mg/L. Only in a few small areas of the northern
and eastern parts does the aquifer yield water with concentrations this low.

Concentrations greater than 1,000 mg/L occur in water in part of the Saginaw Bay Area
and form a band that extends to the north-central part of the aquifer. Chloride
concentrations in water from about one half of the areal extent of the aquifer and range
from 10 to 1,000 mg/L. Sources of chloride for water in the Grand River-Saginaw aquifer
may be fi'om dissolution of halite (NaCl), probably incorporated in the glacial drift (Wood,

1969) or from mixing with brine from the Parma-Bayport aquifer.
DISSOLVED SULFATE

Concentrations of dissolved sulfate from the Grand River-Saginaw aquifer range
from 0.2 to 3,500 mg/L with a geometric mean of 56.0 mg/L. Sulfate concentrations do
not exhibit concentration trends similar to those observed for dissolved-solids and
dissolved chloride distributions (Figures 12 and 13). Water from the southern part of the
aquifer generally has a dissolved sulfate concentration less than 100 mg/L and, locally, less
than 10 mg/L (Figure 14). Concentrations of less than 100 mg/L also occur in water fiom
an area within the Saginaw Bay Area and from the eastern edge of the aquifer toward the
basin center as well as an area in the basin center. The area of low sulfate concentration in
the Saginaw Bay Area may be due to sulfate reduction shown to be a process, taking place
in the Saginaw Bay Area based on the interpretation of stable isotope ratios of carbon and
sulfur fi'om ground water (Long, and others, 1988). Sulfate concentrations greater than
1,000 mg/L occur in water from parts of the west-central portion of the aquifer. The
distribution of high sulfate concentrations in the southwest part of the aquifer coincides
with the location of Jurassic deposits that contain gypsum (CaSO4-2H20) (Cohee, 1965),

that may dissolve to provide sulfate to ground water. High sulfate concentrations in the

32

 

 

 

 

 

 

 

 

 

< 10 mg/L
,5 [:Z] >10 to < 100
m >100 to < 1,000 m
-l > 1,000mg/L
44 —
No Data
xxxxx xx ‘
r/
W
43 5*
o
Pennsylvanian—Mississippian
Contact
42 —
10 o I» n so a 50" BaaefiumU.S.Geok>gical
unreasonab- Surveylfimflnmap

Figure 14. Diasolvedsulfatecmcenhafiundisuibufionmapforgwundwater

 

33

north-central part of the aquifer may be influenced by Jurassic deposits located directly to
the west (Cohee, 1965). Gypsum (CaSO4-2H20) and anhydrite (CaSO4) is believed to
be unevenly distributed in the overlying glacial deposits and dissolution of these minerals
may be providing an additional source of sulfate to the Grand River-Saginaw aquifer

(Wood, 1969).
HYDROCHEMICAL FACIES AND PIPER PLOTS

The concept of hydrochemical facies is a means of describing the diagnostic
chemical character of water (Back, 1961). Piper (1944) developed a diagram, commonly
referred to as a Piper plot, that enables the classification of waters using six chemical
components that allows easy visual chemical comparisons of the chemistry of water
samples, identification of water having different characteristics, evaluation of mixing
among water having difi‘erent characteristics, and determination of the chemical evolution
of ground water. The chemical components used consist of three cationic Ca, Mg, and
Na+K and three anionic Cl, HCO3+CO3, and S04 species or groups of species as these
ions account for the electrical balance in most natural waters (Hem, 1989). Construction
of the diagram entails converting cation and anion concentrations to units of
milliequivalents per liter and then calculating relative percentages of the cation and anion
species or groups of species. The cations and anions each sum to 100%. Each sample is
plotted on respective cation and anion ternary diagrams and on a central diamond-shaped
diagram (Figure 15a). The sample location on the diamond diagram is determined by the
intersection of projections from its position in the cation and anion ternary diagrams. The
projections are made along lines that are parallel to Na+K and HCO3+CO3 axes. The
intersection of the projections represents the composition of the water concerning six

chemical components and is the basis for identifying the hydrochemical facies of a ground-

34

ARE on.

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35

water sample (Figure 15a). Hydrochemical facies are used to classify the chemical
composition of ground water in terms of the dominant cation and anion.

The dominance criteria is based on percentage of milliequivalents of major cations
(Ca, Mg, and Na + K) and major anions (Cl, 804, and HCO3 +CO3) within the sample.
For example, in water dominated by sodium and chloride (Na-Cl facies), the sodium and
chloride ions would be greater than 50 percent of the total cations and anions,
respectively. A water sample that has no cation or anion that exceeds 50 percent of the
total cations or anions is grouped as a no dominant cation or no dominant anion facies.

The data used to construct the Piper plot for the Grand River-Saginaw aquifer
consists of 237 water samples with less than 10% charge imbalance. A major limitation in
making interpretations from Piper plots is that water samples with very different dissolved-
solids concentrations, but with the same relative proportions of cation and anion species
will plot at the same position on the diagram. This limitation can be handled in many ways
(Hem, 1989). In this report we chose to handle this limitation by constructing three Piper
plots (Figures 15b to 15d) in which the samples are grouped as a function of dissolved
solids. The ranges of dissolved solids are less than 750 mg/L, 753 to 2,000 mg/L, and
greater than 2,000 mg/L.

At all ranges of dissolved solids, water samples in the cation ternary diagram plot
along a line with very little scatter from the Ca-dominant area to the Na-dominant area.
Samples are weighted to Ca dominant at low dissolved solids (Figure 15b) and Na
dominant at high dissolved-solids (Figure 15d). Water samples in the anion ternary
diagram plot between HCO3 + CO3 - 804 dominant at low dissolved solids (Figure 15b),
among HCO3 + C03 - Cl - SO4 dominant at intermediate dissolved solids (Figure 15c)
and Cl - $04 dominant at high dissolved solids (Figure 15d). Distribution in Figures 15b
and 15c show more concentrated waters in each interval plotting closer to the SO4-Cl

dominant area. The change in the distribution pattern of the data in the diamond area as a

36

is is

coed :9: 5803 2.2855050 «6:8 oco.N 8 38 Eat 20283850 “6:9.
6039.36 :23 5:23 Bufiwumdga 9:20 328$. 53’ 3:33 Bacmwam¢o>a 2.20
05 E 533 959% com 83 Sailévm— Bawfi of E cogukvcsoE .8 83 .unE--.Aon_ 23mm

 

 

    

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37

function of increasing dissolved solids reflects those changes in the cation and anion
ternary diagrams.

The pattern changes in the ternary and diamond diagrams are consistent with the
hypothesis in which waters with different compositions are mixing. At low dissolved
solids concentrations, meteoric water frequently evolves from a Na or Ca - $04 dominant
rain solution to a Ca - HCO3 dominant ground water solution (Berner and Berner 1987).
Such an evolutionary pathway could explain the trends on Figure 15b. At high dissolved-
solids concentrations, ground water masses that are Na - Cl and Ca - SO4 dominant are
frequently found because of the dissolution of halite (NaCl), gypsum (CaSO4-2H20), and
anhydrite (CaSO4); or the presence of formation brine (Na - Ca - Cl rich solutions).
Mixing among such water could explain the trends (Figure 15d). The trends at
intermediate dissolved-solids concentrations (Figure 15c) are most likely the result of
mixing of water masses of low dissolved-solids concentrations (Figure 15b) and high
dissolved solids concentrations (Figure 15d).

A hydrochemical facies map for Grand River-Saginaw aquifer (Figure 16) was
prepared to show the areal distribution of significant chemical aspects of the facies as
classified on the Piper plot (Figures 15b to 15d). There are three dominant hydrochemical
facies observed in ground water from the Grand River-Saginaw aquifer; Ca-HC03, Ca-
SO4, and Na-Cl. Locally, Na-HCO3 as well as Na-SO4 facies are present. Ground water
in the southern part of the Grand River Saginaw aquifer is dominated by Ca-HC03 facies.
Calcium-bicarbonate facies are typical of water recently recharged. (Back, 1961; Berner
and Berner, 1987). The distribution of Ca-HCO3 facies in the Grand River-Saginaw
aquifer mimics the distribution with that found in the overlying Glacial-Drift aquifer
(W ahrer, 1993). Calcium-sulfate facies are found in the west-central and northeastern
regions of the aquifer and, in part of the Saginaw Bay Area extending out into the basin
center, sodium-chloride facies are mainly present. Calcium-sulfate facies are most likely

influenced by Jurassic deposits overlaying parts of the aquifer in the southwest and

38

 

 

 

 

 

 

 

 

 

 

 

 

 

as 85 3‘
Hyrochemical Facres
[:1 woo. - mm
45
Na-HCOa- ND-Cl
I- 0.404 W “ND
m m
44 —
No Data
x)!
' x ,3
{ wig.
43 ®
Pennsylvanian-Mississippian
42 — Contact

 

h—H—l—I—‘A
‘° °._.'°_._'."_._L‘L:_"' BasefnmUS. Geological
tooromsooso Wlm’mm

Figure 16. Hydroduniculfaciumapforgrunlwaterfiunfin

 

39

upgradient in the north-central parts. Sodium-chloride facies present in and around the
Saginaw Bay Area could be the result of halite dissolution in the overlying glacial deposits
or from mixing with upwelling brine in that area. Separating Ca-SO4 and Na-Cl facies in
the north-central part of the aquifer is an area of Na-SO4 facies. The Na-SO4 facies are
believed to be the result of a mixture of sodium-chloride and calcium-sulfate facies in that
part of the aquifer. Sodium-bicarbonate facies are found along the eastern edge of the
aquifer and are believed to be derived from mixing between sodium-chloride facies and

calcium-bicarbonate facies.

PARMA-BAYPORT AQUIFER

Limited chemical data are available for ground water from the Parma-Bayport aquifer
(ll chemical and 6 isotope samples). Figure 10 shows sample locations for the Parma-
Bayport aquifer. The distribution of hydrochemical facies for water from the Parma-
Bayport aquifer is similar to the distribution in the Grand River-Saginaw aquifer.
However, distributions of chloride, dissolved solids and sulfate differ from the trends
observed in the Grand River-Saginaw aquifer. Chloride concentrations exceed 100,000
mg/L in the Saginaw Bay Area and west-central parts of the aquifer. Dissolved-solids
concentrations are more than 200,000 mg/L in the Saginaw Bay Area and west-central
part of the aquifer. Sulfate concentrations are similar to those of the Grand River-
Saginaw aquifer in the south, but are more concentrated in the Saginaw Bay Area, with
values as high as 3,796 mg/L.

40

SUMMARY

Geochemical distribution maps based on chemical analyses of ground water from the
Grand River-Saginaw aquifer were prepared. The maps show spatial distributions of
dissolved-solids, dissolved chloride, dissolved sulfate, and hydrochemical facies.

Concentrations of dissolved-solids and chloride in the Grand River-Saginaw aquifer
show an increasing trend toward the Saginaw Bay Area from the fringes of the study area.
Source of solutes for dissolved solids in the south and southeastern parts of the aquifer
may be derived from rock-water interaction in the Grand River-Saginaw aquifer or from
rock water interaction occurring in the overlying glacial deposits prior to recharge into the
Grand River-Saginaw aquifer. Solutes also may be derived from mixing or dilution of
underlying brine in the Parma-Bayport aquifer. Chloride sources may also be related to a
brine source or from dissolution of halite probably incorporated in overlying glacial drift
(Wood, 1969).

Dissolved sulfate concentrations throughout the basin show no apparent trends. Low
concentrations of sulfate in the Saginaw Bay Area may be due to sulfate reduction shown
to be a process proven to be taking place through interpretation of stable isotOpe ratios of
C and S from groundwater in that region (Long and others, 1988). High concentrations
of sulfate may be due to dissolution of gypsum in Jurassic deposits (Cohee and others,
1951) or from gypsum and anhydrite unevenly distributed in the overlying glacial deposits
(Wood, 1969). '

Distribution of data on Piper plots (Figures 15b to d) show a cation trend from Ca
dominant at low dissolved solids to Na dominant at high dissolved solids, and also an
anion trend from HCO3+CO3-SO4 dominant at low dissolved solids to HCO3+CO3-
SO4-Cl at intermediate dissolved solids to Cl-SO4 dominant at high dissolved solids.
These three trends indicate a mixing of water masses of various compositions. Three main

facies are present in the Grand River-Saginaw aquifer: Ca-HCO3, Ca-SO4, and Na-Cl.

41

Calcium-bicarbonate facies are found mainly in the south consistent with waters recently
recharged (Back, 1961; Berner and Berner, 1987). Calcium-sulfate facies are mainly
located in the west-central and northeastern areas and sodium-chloride facies are found in
the Saginaw Bay Area.

The overall distribution of data on the dissolved-solids, dissolved chloride and
hydrochemical facies maps indicates mixing as a possible mechanism to explain
distribution patterns observed for waters in the central part of the study area. However,
chemical processes must also be considered as factors afl‘ecting the solute concentrations
of dilute waters in the system. The scatter of data on the Piper diagrams, specifically for
the waters of low concentrations (< 750 mg/L), may indicate chemical processes as well as
physical processes are impacting water chemistry. Also the chemistry of the dilute
samples in the Pennsylvanian aquifers, specifically in the south, is most likely to be
controlled by water derived fi'om the Glacial-Drift aquifer that are controlled by chemical
processes as indicated by Wood (1969). The chemistry of more concentrated samples,
such as in the center of the study area and in the Saginaw Bay Area are shown to be
impacted by physical processes (Long et al, 1988). The following sections analyze
chemical data fi'om the Parma-Bayport and Grand River-Saginaw aquifers to examine the

extent of chemical and physical processes affecting their water chemistry.

CHAPTER 3: GRAPHICAL DATA REDUCTION AND RESULTS

INTRODUCTION

Determining the source for solutes in ground water fi'om the Pennsylvanian aquifers
involves not only addressing the origin and evolution of brine in the Parma-Bayport
aquifer but also investigating the impact of brine fi'om the Parma-Bayport on water
chemistry of the Grand River-Saginaw aquifer. A brine source for solutes for many waters
in the Grand River-Saginaw aquifer is proposed and data reduction techniques will focus
on this idea. Specifically, analysis of Cl/Br ratios for ground water in the Pennsylvanian
aquifers will be used to evaluate the source of CI in the aquifers.

Another type of data reduction implemented in this study involves plotting log ion
(Ca, Mg, 804 etc.) versus log Br and log C1 to investigate the origin of brine in the system
and decipher the impact of brine afi‘ecting the chemistry of water found in the Grand
River-Saginaw aquifer. Brine is known to exist in the Pennsylvanian bedrock sequence as
shown in Figure 3 and formation brine is also present in the underlying Mississippian and
Devonian formations. Wilson and Long, (1993) determined the origin of brine in the
Devonian Formations from evapo-concentrated seawater and brine in the Marshall aquifer
has been shown to have originated through the evaporative concentration of seawater
(Meissner, et al., 1992). By analogy to conclusion of brine origin in the Devonian
Formations and Marshall aquifer a similar origin for brine in the Parrna-Bayport is
suggested. Chemical data from the Devonian-age Traverse Group and the Marshall
aquifer will be used to compare to brine chemistry in the Parma-Bayport to help in the
interpretation of the origin and evolution of the Parrna-Bayport brine. Also the brine
chemistry of the Parrna-Bayport will be compared with concentrated water ( > 750 TDS)
in the Grand River-Saginaw aquifer to aid in the interpretation of the source for solutes of

these waters.

42

43

CL/BR RATIO ANALYSIS

Chloride/bromide ratios are useful in the determination of the source of CI for a given
water chemistry. A solution derived through the dissolution of halite would have a Cl/Br
ratio of around 3025 (Wilson and Long, 1984), whereas brine in the Michigan basin has
Cl/Br ratios ranging from 400 to 600 (Wilson, 1989). The great difi‘erence in Cl/Br ratios
that a result from difi‘erent sources of Cl enables the identification of the major source of
Cl for a water sample.

Figure 17 is a frequency histogram of data from Grand River-Saginaw aquifer, with
values ranging from 7.5 to 1500, with a mean of 367. Distributions of data on the
histogram show a strong correlation to Michigan basin brine ion ratios. Many samples
plot within brine Cl/Br ratio zone indicating water in the Grand River-Saginaw aquifer is
genetically related to formation brine in the Michigan basin. Limited Br data from the
most concentrated Parma-Bayport samples prohibits detailed discussion. The data
plotting to the lefi of the Michigan basin brine ratios may indicate fresher water mixing

lwith brine causing dilution of the CVBr ratio below 400 expected for brine. Other data
plotting to the right of the brine ratio show some dissolution of halite may affect water
chemistry. Halite is known to be heterogeneously distributed in the overlying glacial drift
(Wood, 1969). Few data exhibit high Cl/Br ratios expected for halite dissolution
indicating halite dissolution is only occurring in isolated areas of the aquifer possibly

related to road salt contamination of ground water.
BRINE/SALINE WATER SOURCE ANALYSIS

Analysis of Cl/Br ratios indicate the major source of CI for waters in the Grand River-

Saginaw aquifer to be from brine. This next section analyzes water in the Pennsylvanian

44

 

    

 

 

 

 

24.“ ' ' Si ' ‘ * wagons... ':

20g Michiganbasin 1

[ GrandRiver-Saginaw;

2‘ 16f Aquifer 'j

a) 121 1

:3 ?\ ‘

U‘ : .

O) -\ . . . -

H >§ Hahtedrssolutroni

LL. 4:\ hasCl/Br=30251
;

o? .......... 19.}...-

0 300 600 900 1200 1500 1800

Cl/Br ratio

Figure 17a. Frequency histogram of C1/Br ratios for ground water sampled
from the Grand River-Saginaw aquifer.

 

I v v T‘r v I v v 1—v vvvvv

 

 

 

10 T l Brine Cl/Br ratio 1
I Michigan basin 1
8 _
8‘ L Parma-Bayport
: ‘ Aquifer
cu 5?
a .
o 4 " ‘
H I .
[L4 _ Halite dissolution .
2 _- has CllBr = 3025 a
O 300 600 900 1200 1500 1800
Cl/Br ratio

Figure 17b. Frequency histogram of Cl/Br ratios for ground water sampled
from the Puma-Bayport aquifer.

45

aquifers to determine the origin and evolution of Parma-Bayport brine and to determine if
the source for solutes for water in the Grand River-Saginaw aquifer are linked to
formation brine in the Michigan basin.

Further investigation of the source for solutes for water in the Pennsylvanian aquifers
applies the concepts deve10ped by Carpenter (1978). Carpenter (1978) demonstrated how
formation water chemistry can be compared with evaporating seawater to make
interpretations as to possible origins and evolutions of brine chemistry. The ideas of
Carpenter, (1978) will be applied first to determine the origin of brine and saline water in
the Pennsylvanian bedrock system and second to compare concentrated water in the
Pennsylvanian units to deeper formation brine on the basin. Making the comparison of
formation water compositions with the evaporation trends of seawater is justified because
the composition of seawater has remained reasonably constant since Cambrian time
(Holland, 1978).

The method proposed by Carpenter (197 8) is based on the premise that brines
produced by the evaporation of sea-water will be moved fiom their point of origin as a
result of sediment compaction, tectonic deformation, and other processes. The result of
this in the case of the Michigan basin is the potential, certainly in the past and possibly
today, for interaction between brine and meteoric water. This mixing between brine and
less concentrated waters in the Michigan basin may be an explanation for the occurrence
of concentrated waters found in the Pennsylvanian bedrock sequence and in the overlying
Glacial-Drift aquifer.

During the evaporative concentration of seawater the ratios of ions within a solution
remain constant until the onset of mineral precipitation. The constant relationship between
ions is expressed as B/A=k or B=kA, where A and B are ions and k is a constant. The
logarithmic form of this equation is: log B = log A + log k and a plot of loglOA versus
loglOB produce a straight line with a 1:1 slope regardless of the value of k; therefore any

ion that deviates fiom this relationship is afi‘ected by processes other than removal of

46

water molecules from solution (Carpenter, 1978). To investigate the chemical history of
brine derived from seawater the use of one or more conservative constituents are required.
A conservative constituent may neither precipitate/dissolve nor participate in diagenetic
reactions with subsequent mineralogical environments (Carpenter, 1978). Hence, a plot of
a conservative ion concentration versus the degree of evaporation would be a straight line.
During the initial evaporation of seawater, both Cl and Br behave conservatively and
increase in concentration, however the CVBr ratio remains constant at its normal seawater
value (Carpenter, 1978; McCafi‘rey et al., 1987). Figure 18 shows that if solutes in water
were derived from the dissolution of halite Cl/Br ratios would plot near region A whereas
solutions plotting near regions B and C are representative of water derived through the
evapo-concentration of seawater (Long, personal commun., 1992). In addition, log
ion:log Br and log ion:log Cl plots can indicate if a brine has been affected by dilution with
seawater or freshwater (Carpenter, 1978). In the following comparisons Br and C1 are
used as conservative indicators for the degree of evaporation reached by seawater fi'om
some of the concentrated waters aquifers and also as an indicator of rock-water
interaction that may have taken place. Chloride was also used as a conservative indicator
as few samples are concentrated beyond halite saturation. IonzBr and ionzCl plots will be
used to evaluate similarities between brine in the Parma-Bayport aquifer and Mississippian
and Devonian brine of the Michigan basin and evaluate hypothesized mixing between brine
and meteoric water in the Pennsylvanian aquifers.

Land and Prezbindowski, (1981) suggest caution must be applied in making the above
interpretations. Land and Prezbindowski, (1981) state if a dissolution reaction was a
reversible chemical reaction and the partitioning coefficient still determined the Cl/Br ratio
in the solid and solution the solution at equilibrium with halite would have a much lower
Cl/Br ratio than suggested above. The result of this is waters formed by halite dissolution
may plot along seawater evaporation trajectory causing erroneous and ambiguous

interpretations. Considering the nature and rates of reactions, brine fiom a reservoir

.fi

LOG10C1(mg/L)
N U)
IHr'IHHIWTTITfl'Ifi'w'fl'r'flrr

H

47

 

 

ITIIIIIIITjIITIIIIITrTfiIIIIleIIIIIIITIII

Seawater A
Seawater
Evaporation
Trajectory

A -- Location of samples derived from halite
dissolution

B and C - solutions derived from evaporation of
seawater

IIIIIIILIII1111IIIIJIIILIIIIIIILIIIIIllll

ILLIIIIILMILLIIJIlllllllLLl111111111

 

 

-3 -2 -1 0 1 2 3 4 5

LOGIO Br (mg/L)

Figure 18. Interpretation of brine origin from location around seawater
evaporation trajectory.

48

formed through halite dissolution that plot as a cluster on the seawater evaporation
trajectory will be expected to be rare (Wilson and Long, 1984). Also Cl/Br ratios
acquired through subaerial evaporation or subsurface interactions with evaporite deposits,
are subsequently preserved for interpretation because these anions generally do not
participate in diagenetic reactions with other minerals (Stuebber and Walter, 1991) making

interpretations of processes afi‘ecting brine chemistry based on ion ratio plots is justified.

m'gig of brine

Figure 19 depicts the relationship between the water chemistry of the Traverse Group,
Marshall aquifer, Parma-Bayport and Grand River-Saginaw aquifers that is consistent with
a model in which freshwater is mixing with formation brine (Long et al, 1993). The more
concentrated waters show a close correspondence with the seawater evaporation
trajectory indicating a source fiom evaporated seawater as plausible for Patina-Bayport
brine. Lesser concentrated waters extend along a concentration continuum indicating
dilution below seawater composition. Data distribution shows a scattering of dilute
waters fiom the Pennsylvanian and Mississippian aquifers indicating a freshwater end-
member with variable Cl and Br concentration exists. This dilute end-member appears to
be mostly unaffected by mixing with more concentrated waters indicating that other
source of solutes exists for the dilute waters in the system.

Sodium-chloride relations are shown on Figures 20 and 21 and provide better
evaluation of the mixing relationships described above from Cl-Br relations as more data
exists. Overall distribution of Figure 20 and 21 shows a similarity between Parma-Bayport
brine with less concentrated Mississippian brine on this diagram as they plot along the
evaporation of trajectory just short of halite saturation. A decreasing degree of
concentration is noted from the Traverse > Marshall > Parma-Bayport > Grand River-

Saginaw aquifer from data distribution on both Figures 20 and 21. As in the previous

Log Cl (ms/L)

Log Cl (mg/L)

49

 

 

  

 

 

 

 

 

 

 

 

 

 

 

 

 

 

c- . . . - a .
: Grand Rrver-Sagmaw aquifer (a) : F Parma-Bayport aquifer (b) 1
. . . 1
5} 1 5P 1
: A : E 1
L L .. Q _'
4_ A 4 g ‘E .
s— 1‘ 3 3L -
. :5 r '
: : : O
3.” “.5 2- ‘
I 3 go - .0
1e {.3 1'- -
_ Seawater Evaporation; .
°h Trajectory ‘ °' ‘
.1-lnllnlnlllllr .lnnnrlrrrnl....l.x..l-A-Al_ '1’]. I‘ll.AAlllLllAALA‘JIAAlAAllll‘A l ALAI—
-3 -2 -l 0 1 2 3 4 5 -3 -2 -1 0 1 2 3 4 5
Log Br (mg/L) Log Br (mg/L)
; Marshall aquifer (c) ; _ Traverse Group (‘1) ,
. . .
s— 3 5~ ~
I . ‘
4;- —g 4— J
3:.- “ a 3: ..
. v .
i .-— I
2:- j 0 2f -
°° :
1'- ‘- 3 1:- "
o} — o:— -
.1; _ _1_ _
l....l....l....lrr..l..r1....l..A_LLAnAL1 1..r.l....lrrrilrrrrlrrirlrrirlrr1.111ALL
6 2 1 0 1 2 3 4 5 3 -2 0 l. 2 3 4 5

Log Br (mg/L) I ' Log Br (mg/L)

Figure 19. Cl-Br relations of ground water from the Grand River-
Saginaw (a), Parma-Bayport (b), and Marshall (c) aquifers
and Traverse Group (d) waters with the evaporation of seawater
trajectory (McCafi'ery et al., 1987).

50

 

 

 

 

 

“-1 I l I l l l l-

_ Grand River-Saginaw aquifer (a) '

5- _'

A I 2

s. I 1

4:- 1

£3.” 1

CU ' 1
Z ’7

A 0: Seawater Evaporation ‘.

E Trajectory I

.11— _

14A#IAAAAIJAAJIAAAAIAAlllllllIJJAAI

-1 o 1 z s 4 s o

LOG c1 (mg/L)

Figure 20a. Na-Cl relations of ground water from the Grand River-Saginaw
aquifer with evaporation of seawater trajectory (McCaffery et al., 1987).

 

vvv—vrv—rvvtvrrf‘VV

Puma-Bayport aquifer (b) :

vtrvvulrrIVI

I v

G

‘ M
-, m-
A
alkali-all

LOG Na (mg/L)

 

 

 

O
2~ 0 _
1; ' . _
o; _
4:. _
I I .l .1 l 1 I
1 0 1 2 3 4 5 6

LOG c1 (mg/L)

Figure 20b. Na-Cl relations of ground water from the Puma-Bayport
aquifer with evaporation of seawater trajectory (McCaffery et al., 1987).

51

 

 

 

6 ' -
5E -I
A > <
$1.4: -:
a E 3
v3; '1‘
t6 : .
z 2- :
(5 1E j
3 i 1
+ ,

0r 1

t 1

'151 .1

 

 

LOG (:1 (mg/L)

Figure 21a. Na-Cl relations of pound water from the Marshall aquifer
with evaporation of seawater trajectory (McCaffery et al., 1987).

 

IfWYYjYYTWIfiVfijVYWYIVVYYIVYVYIYVYVI
7- —l

Traverse Group (1:)

'7'

LOG Na (mg/L)

 

 

 

5
13 —.
E I
0:» 5
43,, 1 1.4.--. .
-1 o 1 2 3 4 5 6
LOGC1(mg/L)

Figure 21b. Na-Cl relations of pound water from the Traverse Group
with evaporation of seawater trajectory (McCaffery et al., 1987).

52

figure a dilute end-member water mass exists that is mostly unafi‘ected by brine chemistry.
Good evidence is provided for a mixing relationship between Pennsylvanian brine with
more dilute Pennsylvanian waters similar to Stueber and Walter, (1991) who showed

dilution of Silurian and Devonian brine by meteoric waters in the Illinois basin.

Chemical Changes in the Subsurface

Departure from an ionzBr or ion:Cl seawater evaporation trajectory indicates changes
in chemical composition of evaporated seawater that has occurred as a result of diagenetic
reactions in the subsurface (Steuber and Walters, 1991). As shown above Na corresponds
well to the seawater evaporation trajectory indicating little impact of rock-water
interaction impacting Na concentrations of more concentrated water.

Potassium-bromide and potassium-chloride relations are shown on Figure 22 and 23
respectively. Data distribution indicates K depletion with respect to the seawater
evaporation trajectory. Carpenter, (1978) suggests a depletion of K from a brine is due to
reactions with low K clay minerals such as kaolinite to produce K rich clays such as illite,
as well as authigenic K-feldspar. Wilson, (1989) attributed alumino-silicate reactions as
the cause for depletion of K in Devonian brine.

Calcium-bromide and calcium-chloride relations are shown on Figures 24 and 25
respectively. Relations between Ca-Cl and Ca-Br reveal Ca enrichment relative to the
seawater evaporation trajectory and a dilution trend extends downward fi'om the most
concentrated samples. Magnesium-bromide and magnesium-chloride relations on Figures
26 and 27 show a complementary depletion in magnesium concentration relative to the
seawater evaporation trajectory. A mechanism to elevate Ca and deplete Mg
concentration is dolomitization of limestone (Carpenter, 1978). Wilson, (1989) in a study
of Devonian and Silurian formation brine of the Michigan basin found dolomitization to be

a major diagenetic reaction controlling Ca and Mg concentrations. In this study Wilson

53

 

 

I I I I I I I I I I I I I T I I I I I I I I I I I I I I I I I I I I I I I I I Ij’
6 A . . . —
— Grand River-Sagrnaw aquifer .
Z O Parma-Bayport aquifer :
I [:1 Marshall aquifer I
A 4 f ‘_
g C Seawater Evaporation ___,_.—«> Z
a 3 F Trajectory D —
v " _
M L _
_ D _
CD 2 r i
1 _— __
0 j j
_ . -
-1 — _

I l I I I I J_1 4L 1 1 I l l l 1 l l I I l l l 1 l I l I I l I l l I I I l l I I

 

 

 

-3 -2 -1 0 1 2 3 4 5
LOG Br (mg/L)

Figure 22. K-Br relations of pound water from Grand River-
Saginaw, Puma-Bayport, and Marshall aquifers with
evaporation of seawater trajectory (McCafiery et al., 1987).

54

 

LOG K (mg/L)

 

6 I I I T I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I
j A Grand River-Saginaw aquifer j
5 I O Parma-Bayport aquifer -
j C] Marshall aquifer j
: Seawater Evaporation/ -
3 :_ Trajectory U L
_ E, 9 _
i a I
2 — U —
I A I
-1 — a _
I I I I I I I I I I I I I I I I J_ I I I I I I I I I I I I I I I I I LI

 

 

 

-1 0 1 2 3 4 5 6
LOG Cl (mg/L)

Figure 23. K-Cl relations of pound water from Grand River-
Saginaw, Puma-Bayport, and Marshall aquifers with
evaporation of seawater trajectory (McCafi'ery et aL, 1987).

55

 

IIIIIIIIIIIIIHIIIIIjIIIIIIIIIIIIIIIITTIII

 

6 T A Grand River-Saginaw aquifer I
5 L O Parma-Bayport aquifer L
[ [:1 Marshall aquifer j
D —r
i 4
— —-J
A 4 - ~
a. I a :
L- .4
E 3 *- i
v Z -
6 - .
0 2 r i
r—I 1 :- j
- A -4
: Seawater Evaporation :
0 _. Trajectory _
i 1
- —J

1 I I I I I I I I I I I I I ALI L I I I I I I I; I I I I I l I I I I I I I I I I I

 

 

 

-3 -2 -1 O 1 2 3 4 5
LOG Br (mg/L)

Figure 24. Ca-Br relations of pound water from Grand River-
Saginaw, Puma-Bayport, and Marshall aquifers with
evaporation of seawater trajectory (McCaffery et al., 1987).

0‘

LOG Ca (mg/L)
N U) &

p—l

-1

56

 

1 I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I j I I
TA Grand River-Saginaw aquifer i
: O Parma-Bayport aquifer :
- Cl Marshall aquifer 3 -
._ D —

D
- U _
r a? t
: c. a De :3 :
L L
r -
.— -J
.— D _
— D D A Seawater Evaporation —
: Trajectory :
I U I
I I I I I I I I I I I I I L L I I I I I I L I I I I I I I I I I I I

 

 

 

 

-1 0 1 2 3 4 5
LOG c1 (mg/L)

Figure 25. Ca-Cl relations of pound water from the Grand River-

Saginaw, Farms-Bayport, and Marshall aquifers with evaporation
of seawater trajectory (McCaffery et al., 1987).

6

57

 

IIIIIIIIIIII‘ITTIIIIIITIUIIIIIIIIIIIIIIITI

 

6 — A o . . ——+
— Grand Rrver-Sagmaw aquifer 4
5 I O Parma-Bayport aquifer I
I '3 Marshall aquifer j
C I
A 4 — D 2
a : Seawater Evaporation M j
- Trajectroy 1
3 3 :- a? i
DD [ I
2 . -
2 a -
“-1 1 r i
C i
o _— __
-1 _ _

A I L L I LA I J L I I I I I I I I I LI I I I I I L I I I I I I I I I I I I J I

 

 

 

-3 -2 -1 O 1 2 3 4 5
LOG Br (mg/L)

Figure 26. Mg-Br relations of pound water from Grand River-
Saginaw, Parma-Bayport, and Marshall aquifers with
evaporation of seawater trajectory (McCaffery et al., 1987).

58

 

 

 

LI I j I I I T I r I I I I I I I I I I I I I I I I T I I I I I I I I T I
6 A Gr T
t and River-Saginaw aquifer -
5: I . Parma-Bayport aquifer Z
. [3 Marshall aquifer :
A ~ 0 ~
% 4 .— Seawater Evaporation -
a : Trajectory % a] D j
v L IDan'él .3
Gt) 3 : D D [E j
2 - .
r .
CD 2 r i
O F j
1 f j
I 1
0 :' D ‘2
r- A -4
" A
r 4
-1 _ I I _I I I I I I I I I I I I I I I I I I I I I I I I I4 I I I I I I I I

 

 

 

-1 0 1 2 3 4 5 6
LOG c1 (mg/L)

Figure 27. Mg-Cl relations of pound water from Grand River-
Saginaw, Parma-Bayport, and Marshall aquifers with
evaporation of seawater trajectory (McCafl‘ery et al., 1987).

59

used the 1:1 relationship of Ca enrichment to Mg depletion through the dolonritization
reaction to test his data. The difference in Mg in each sample and equivalently
concentrated seawater was calculated based on measured Br in each sample. This Mg
deficiency was assumed to result only from dolonritization and so was converted to a
predicted Ca concentration based on a 1 for 1 mole replacement. Wilson then adjusted the
predicted Ca for CaSO4 dissolution and then compared Ca to Mg. Similar enrichment and
depletion behavior in Ca and Mg concentrations are noted in Parma-Bayport waters,
however the degree of enrichment and depletion is not 1:1 as Wilson found for Devonian
brines. Specifically, 2 data points, one from the western region of the study area and one
fiom the center of the study area are more Ca enriched than Mg depleted indicating an
additional control on Ca concentration than dolomitization. The added Ca could be the
result of gypsum dissolution known to exist in Jurassic deposits in that part of the study
area. Unfortunately, no sulfate data exists for the two westernmost samples to investigate
this hypothesis. Three data points in Saginaw Bay Area indicate an even Mg depletion
and Ca enrichment similar to Marshall and Devonian brine. Similar to previous Figures,
Ca and Mg relations relative to Cl and Br indicate a dilute end-member water not related
to brine chemistry.

Sulfate-bromide and sulfate-chloride relations are shown on Figure 28 and 29. In all
three aquifers sulfate depletion is noted with respect to the seawater evaporation
trajectory. Wilson, (1991) noted sulfate reduction as a process causing depletion of
sulfate in Devonian and Silurian formation brine. A similar data distribution exists for the
Marshall and Parma-Bayport aquifer brine implying a similar process is impacting or has
impacted these waters. The distribution of Parma-Bayport brine data on Figure 29
appears to bridge the gap between Marshall brine samples and concentrated waters fi'om
the Grand River-Saginaw aquifer. This distribution does not appear top be a artifact of
sampling from the Marshall aquifer as analysis of Cl and S04 distribution maps for the

Marshall aquifer indicate that no waters exists in the aquifer with Cl and 804

60

 

 

I If I I I I I I I I I I j I I I I I I I I I I I I I I I I I I I I I I I I I I I I
6 .— A Grand River-Saginaw aquifer i
I O Parma-Bayport aquifer :
5 _ _
: C] Marshall aquifer j
A 4 .— j
i I A A 93 an I
A
3 ‘ A A D "
0‘" : arm 0 a :
U) 2 .— Dg A _—
_ A _
8 - D$§ _
1 _— _
r—l - .l
__ Seawater Eva ration _‘
0 P0
- Trajectory ‘
-1 — _
I l I I I I 14L I I I I I I I I | I I I I l 1 I I I l I I I I I I 1 I I I I I I I

 

 

 

-3 -2 -1 0 1 2 3 4 5
LOG Br (mg/L)

Figure 28. SO4-Br relations of pound water from Grand River-
Saginaw, Farms-Bayport, and Marshall aquifers with
evaporation of seawater trajectory (McCaffery et al., 1987).

61

 

 

T I I I I I T I I I I I I I I I I fr I T I I I I I I I I I I I I I I I

6 :A Grand River-Saginaw aquifer _—

5 : O Parma-Bayport aquifer :

C C! Marshall aquifer 2

r Seawater Evaporation -

a: 4 L Trajectory \ _‘
I _

E 3 L __
OH" I j
V) 2 ; _‘
r—l 1 :— €
0 _— _

_ 1

I A A I

-1 L l I I I I l I I LI I I I I I I I I I I I I I I I I I I I I4 I I I I —

 

 

 

I
I—l

0 1 2 3 4 5 6
LOG (:1 (mg/L)

Figure 29.804-C1 relations of ground water from Grand River-
Saginaw, Patina-Bayport, and Marshall aquifers with
evaporation of seawater trajectory (McCafi'ery et al.,1987).

62

concentrations necessary to plot in that region of Figure 29. This may indicate that the
Marshall brine is mostly isolated from mixing with fluids in overlying aquifers and that the
major source for solutes for the more concentrated waters in the Grand River-Saginaw

aquifer are derived primarily from the Parma-Bayport brine.

Cmter Function Analysis

A further test to link the chemistry of Michigan basin brine with the chemistry of
Pennsylvanian groundwaters relies on Carpenter's, (197 8) approach to account for
diagenetic reactions involving divalent cations and carbonate and sulfate minerals to
deduce whether a brine originated from evaporation of seawater followed by such
reactions or if the brine had a more complex origin. Added complexities might include
diagenetic reactions involving monovalent cations, silicate minerals or halite. The quantity

of divalent cations charge balanced by only Cl was defined by:
CF=Ca+Mg+Sr~HCO3 - $04

This approach is defined as the Carpenter Function (CF). Plot CF versus Br, and
evaporating seawater defines a trajectory unaffected by dolomitization, recrystallization or
precipitation of CaCO3 or CaSO4 precipitation (Carpenter, 1978). Plots of CF versus Br
and Cl versus CF were prepared to fiirther correlate water chemistry of concentrated
waters in the Pennsylvanian units to that of underlying brine. The CF values for brine
samples were calculated using the formula:
CF = Ca + Mg -SO4

because HCO3 concentrations are low.

Figure 30 indicates a trend of the more concentrated samples toward the seawater

evaporation trajectory for limited Pennsylvanian water samples. This distribution of data

 

63

 

 

 

 

‘vvvv ' .v

 

 

 

 

 

 

 

 

 

 

 

 

fififi.” .. ._ “W, _

Grand River-Saginaw aquifer (a) 3 C Parma-Bayport aquifer (b)

3." — a} _‘

A; / 3 $9. / 3

g . A I «a: ' 3

Er:- — Ei- —

I3 AA g1 . E 3

016mg _ 0F . _

- A F l

"7 AA AA A A ‘ "I 1

:A A A SeawaterEvaporationf ; j

.2; ‘_‘_I III. I Trqmq. I I; .2; I I l I I I

-3 -I. 0 I 2 3 4 -2 -I 0 1 Z 3 4
IDG Br (mg/L) LOG Br (mg/L)

‘ I I I I I I I_ 4”I I I I-l

: Marshall aQuifer D (c) 3 E Traverse Group fiw):

a} ‘_ 3' / * 1

E3 f/ : E -;

5 3 D I 5 :

r— — 1— ~

6 g or??? : e _ :

§.-. 0” ED 2 w ._ 3

: ӣ30 a : 8 :

I a DD 0 I I I

4; El D C] I '1.— E

.2LIA IIAAAAIAAIAI IA I. .I- .2;IAAAAJ_IAAAJJJAAIAAALIALLLLL A_A :

-2 -I 0 I 2 3 l -2 -l 0 I 2 3 4
DOG Br (mg/L) LOG Br (mg/L)

Figure 30. Carpenter Function (CF)-Br relations of ground water from the Grand
River-Sagianw (a), Parma-Bayport (b), and Marshall aquifers (c), and
Traverse Group (d) waters with evaporation of seawater trajectory

(McCaffery et al., 1987).

64

compliments ClzBr (Figure 19) and NazCl (Figures 20 and 21) plots by indicating a mixing
of waters in the Michigan basin. A similar distribution is recognized for Marshall and
Traverse samples that plot to the left of the seawater evaporation trajectory line. The
Cl:CF (Figure 31) plot is also similar to the ClzBr and NarCl plots in matching the
seawater trend, however the Cl:CF plot apparently reflects higher degrees of evapo-
concentration than are predicted by other plots. The overall data distribution on Figure 31
shows an excellent decreasing degree of concentration from Devonian to Marshall which
plot beyond halite precipitation to Parma-Bayport and then to Grand River-Saginaw
samples plotting above and near to seawater composition. A dilution trend is apparent for
concentrated Mississippian and Pennsylvanian waters extending downward from seawater
composition. This concentration continuum implies a common origin for solutes for water
>750 mg/L in the system. One interesting trend noted on Figure 31 is 1 sample from the
Grand River-Saginaw and 3 samples from the Patina-Bayport plot to the lefi of the
seawater evaporation trajectory whereas all data but 1 sample analyzed from the Marshall
and 1 from the Traverse-Dundee plot to the right of the line. This CI enrichment indicated
by a few Pennsylvanian waters poses an interesting problem not presented in other figures
thus far. This problem may be explained one of three ways: 1) This data although hardly
representative of the entire Parma-Bayport brine may indicate that it is not entirely similar
to the deeper formation brine present in the basin and does not share a similar evolutionary
history; 2) even though previous plots indicate chemical similarities with limited data from
the Parma-Bayport one cannot completely exclude the possibility that the Parma-Bayport
brine was not affected by other diagenetic alterations than those of deeper formation brine
in the basin ; 3) analytical error associated with sampling a brine may skew these data as
the quality of the Parma-Bayport brine data must be considered. The third explanation

provided above seems the most likely choice.

65

 

IV 'IrYV VY—VIV—Trjj

V V V I 'f"

l—
p
p
p
.—

 

 

 

River-Saginaw aquifer (a)?

 

 

 

 

 

 

; Seawateeraporation

C Trajectory

FIII I I IJIAAAklaaagAaaal

.2 .1 o r z 3 4
LOGCF(meq/L)

,....,...rr.r..,s..fifi. ,....,-

. Marshallaquifer (°)3

i" °° .9;

L93 “”3150 a

: DUO 0 :v

: KP 55

E (E1 Dar: 2

.O @1 28

r .3 [In a ‘:-l

I D I

E ‘2

bILII.IAAAAI....I....I.+I.I.IIII;

.2 .1 o r 2 3 4
LOGCF(meq/L)

N U A

p

ITYrVIYTYrIfiVV

 

 

 

 

 

I T V ‘Y Y I Y V V V I V V V V I I T Y r Y T V V I I V V V I
* Patina-Bayport aquifer (b) :
I 1
b d
I. o l
b 1
b q
p q
r u
)— c-l
I- 1
L ;
d
4
*- 1
t i
b q
L o _‘
: :
b d
F 4
’- I l I I I I L I I I I . 1 fl

-2 l 0 1 2 3 4

LOG CF (meq/L)

' V I V V ‘7 V ‘ V 7 V V I V V V Y I V V Y fi "T Yfi
E Traverse Group (‘0 f
r 1

 

.II.-..I.II.I

 

 

ol 0 1 2
LOG CF (meq/L)

Figure 31. CF (Carpenter Function)-Cl relations of ground water
from the Grand River-Saginaw (a), Patina-Bayport (b),
and Marshall aquifers (c) and Traverse Group water (d)
with evaporation of seawater trajectory (McCafi'ery et al., 1987).

66

SUNINIARY

Frequency histograms of Cl/Br ratios of water fi'om Grand River-Saginaw and Parma-
Bayport aquifers indicate the major source of Cl is more likely fiom a brine source than
from the dissolution of halite. This points to the importance of the Parma-Bayport brine
as a source of solutes to concentrated waters of the Grand River-Saginaw aquifer.

It appears that Cl:Br (Figure 19) and Na:Cl (Figures 20 and 21) relations imply that the
origin of brine in the Parma-Bayport aquifer is from evaporative concentrated seawater
just short of halite saturation and KzBr and KzCl (Figures 22 and 23), CazBr and Cl
(Figures 24 and 25), Mngr and Cl (Figures 26 and 27), and SO4zBr and Cl (Figures 28
and 29) show the more concentrated waters may be affected by alumino-silicate reactions,
some degree of dolomitization, and sulfate reduction, and possibly affected by gypsum
dissolution. Without more data from the aquifer a definitive origin of the brine cannot be
reached. Data from brine in the Parma-Bayport was found to be geochemically similar to
brine found in the Marshall Sandstone and Traverse Group albeit not as concentrated,
lending credibility to its implied origin, even though a slight deviation is noted from CFzCl
plot (Figure 31).

IonzBr and ionzCl relations (Figures 19-31) indicate a link between the Parma-Bayport
brine and concentrated waters from the Grand River-Saginaw aquifer. The Parma-
Bayport brine appears to provide the source for solutes for much of the Grand River-
Saginaw aquifer. A concentration continuum observed on Figures 19 to 31 imply a
common origin for solutes of more concentrated waters in the system. Also the ionzBr
and ionzCl relations show that not only a CI-rich end-member water mass (Parrna-Bayport
brine) exists but also a dilute end-member water mass is important in explaining the
geochemistry of all waters in the Pennsylvanian aquifers. The Cl-rich end-member is
shown to be impacting the water chemistry of ground water in the Grand River-Saginaw

aquifer indicated by the mixing trend downward from the seawater evaporation trajectory

67

on ionzBr and ionzCl plots. The scatter of data associated with the dilute end-member
indicates that these samples are mostly isolated fiom interaction with brine as a source of
solutes and therefore the solutes are derived from a different source, i.e., rock-water
interaction. Figure 32 summarizes location of water masses discussed on the previous
diagrams.

It is important to note the location of the dilute and more concentrated water masses of
the Grand River-Saginaw aquifer discussed. In general the more concentrated water is
mainly found in and around the Saginaw Bay Area as well as the east-center part of the
study area. Dilute water in the system is typically located in the southern part of the
aquifer as well as around the fringes of the aquifer. These generalized distributions are not
an artifact of sampling for what they do indicate is that different processes are operating in

different parts of the aquifer controlling ground water chemistry.

68

 

IIIITIIIFIIIIIIIIIIVIIIIIIIIIITIIIIIIIITI

 

 

H

 

6 r
_ Brine
5 r
A 4 r
g : Seawater
a _ Evaporation
v 3 E“ Trajectory
.—
8 2 r Seawater
r
A ; freshwater
1—
I.

Location of water masses represented on ion:Br and ion:Cl plots

IIII¥IIIIIIIIILLIIIIIIIIIIIIIIIIIIIIIIIII

 

IIIIIIIIIIIIJLIIIIIIIIIIIIIIIIIIIIII

 

 

-3 -2 -1 O 1 2 3 4 5
LOG Br (mg/L)

Figure 32. Cl-Br relations with evaporation of seawater trajectory presenting
the location of water masses portrayed on a generalized Cl:Br plot.
Designated locations on the figure are based on trends portrayed on
previous diagrams (figures 19 to 31).

 

CHAPTER 4' I-IEMICAL MODELING

INTRODUCTION

An additional technique used to determine controls on the chemistry of natural waters
involves the use of geochemical models. The chemistry of groundwaters may be greatly
influenced by rock-water interactions and a geochemical model, such as WATEQ4F, can
be used to determine which dissolution precipitation and oxidation-reduction reactions
may be proceeding in the aquifer. As indicated earlier a source of solutes for more
concentrated water in the Pennsylvanian aquifers appears to be fi'om brine present in the
deeper Pennsylvanian system and in the Mississippian and Devonian bedrock sequences.
The dilute end-member (dissolved solids <75 0) present in many of the diagrams above
seems mostly unimpacted by the brine chemistry and therefore the solutes in these less
concentrated waters must be supplied from a difl‘erent source, i.e. rock water interaction
or from solutes derived from the Glacial-Drifi aquifer. Wood, (1969) indicated in the
southern portion of the Pennsylvanian subcrop that water in the overlying Glacial-Drifi
aquifer was more concentrated than the water in the Grand River-Saginaw aquifer
indicating a source of solutes to the Grand River-Saginaw aquifer from the Glacial-Drift
aquifer and the potentiometric surface indicates a hydraulic connection between the drift
and Grand River-Saginaw aquifer.

WATEQ4F, a chemical speciation code for natural waters was used to model water
from the Grand River-Saginaw aquifer. The model uses field measurements of
temperature, pH, Eh, dissolved oxygen, alkalinity, the chemical analysis of a water sample
and calculated density of each sample as input and calculates the distribution of aqueous
species, ion activities and mineral saturation indices that indicate the tendency of a water
to precipitate or dissolve a set of minerals (Ball et al, 1991). WATEQ4F achieves this by
relying on the concepts of thermodynamic equilibrium, the Debye-Huckel/ B dot equation

69

70

for activity coemcients and experimental equilibrium and speciation constants and by
iteratively solving a series of simultaneous equations that determine equilibrium constants
and mass balance equations for each component in the system. The calculation provides
saturation indices (SI) of minerals that may be reacting in the system. The SI of a

particular mineral is defined as:

SI = log 1’33
Kt

where IAP is the ion activity product of the mineral water reaction and Kt is the
thermodynamic equilibrium constant adjusted to the temperature of the given sample. The
SI is approximately equal to 0 when a water sample is at equilibrium with a particular
mineral phase. When the SI is greater than 0 the water is supersaturated with respect to
that mineral and the precipitation of that mineral would be possible. An SI less than 0
indicates undersaturation with respect to the mineral phase and suggests the mineral will
undergo dissolution. Speciation calculations show the reliable results up to the ionic
strength of seawater (ionic strength=.72) (Ball and Nordstrom, 1991). Only one sample
exceeded this degree of concentration in the Grand River-Saginaw aquifer, all other data
fall within the limits of the model. The success of the model is dependent upon high
quality data and accurate and internally consistent thermodynamic data base. Data with
only less than 10 percent difference in charge balance were modeled and the most
complete thermodynamic data set available for solubility product constants and ion
association constants including data from Nordstrom et al., (1990) was used. Table 2
includes equilibrium constants used in modeling.

The chemical model WATEQ4F was implemented to analyze the degree in which
mineral components of the aquifers may be reacting with groundwater. Three mineral

systems will be investigated: the carbonate system (calcite, dolomite and aragonite),

Table 2. Selected Thermodynamic data used in WATEQ4F calculations of saturation

 

 

 

 

 

 

 

 

 

indices.

MINERAL NAME LOG K REFERENCE

Anhydrite -4.36 Nordstrom et al., (1990)

Aragonite -8.336 Plummer and Busenberg,
(1982)

Calcite -8.48 Plummer and Busenberg,
(1982)

Chalcedony -3.55 Nordstrom et al., (1990)

Dolomite -16.S4 Nordstrom et al., (1990)

Gypsum -4.58 Nordstrom et al., (1990)

Halite 1.582 Robie and Waldbaum,
(1968)

Quartz -3.98 Nordstrom et al., (1990)

 

 

 

 

 

 

 

72

evaporite minerals (gypsum, anhydrite, and halite), and silicate and alumina-silicate
minerals (quartz and chalcedony). The mineral phases chosen are a reflection of aquifer
matrix and aquifer cements (carbonate minerals and silica), evaporites were chosen due to
presence in overlying Glacial-Drift aquifer and Jurassic deposits. The output fi'om the
model pertaining to these minerals will be used in evaluating their impact on water
chemistry in the Grand River-Saginaw aquifer. Frequency histograms and discussion of
the distribution of mineral saturation index values from selected compounds are one result
of chemical modeling. Also activity-activity or mineral stability diagrams are useful in

interpreting chemical modeling data.

Dgsity Dgermination

The density of each water was used as input for the model and therefore needed to be
calculated. The density of water varies with temperature and salinity and it is possible to
calculate the density of a water sample by using a series of equations described by
Gudramovics, (1981). At constant temperature, the relationship between density and
salinity is linear. Salinity was estimated from the chloride concentration by equation (1)
(Schopf, 1980):

(1) Salinity (%o) = 1.80655 4: (Cl (%o))
To calculate the density of water at the measured temperature in the well, the value of the
y-intercept and slope must be calculated. The y-intercept refers to the density of pure

water at a specified temperature and is determined through equation (2) (W east, 1979):

(2) y-intercept = (999.83952 + 16.945176: T - 7.9870401: 10-3 T2 -
46.170461 4: 10-6 r3 + 10556302 6 10-9 r4 - 280.54253

«- n1

73
4 10 -12 T5) / (1 + 16.87985 .1 10-3 4 T) a. 1000
The slope for the specified temperature is calculated by equation (3) (Home, 1969):
(3) Slope = 8.300245 .. 10-4 - 2.2274915 s 10-5 4 In T

Once the salinity, y-intercept and slope were calculated at the temperature of the sample,

the density was calculated by equation (4):

(4) Density = (Salinity 4 Slope) + y-intercept

RESULTS AND DISCUSSION

Cgbgnate Minerals

Figures 33, 34 and 35 show distribution of saturation indices for calcite, aragonite, and
dolomite. Average calcite saturation index of .054 indicates that calcite is near equilibrium
with waters throughout most of the aquifer. Calcite SI distribution shows some 1&-
supersaturation with respect to calcite in the southern portion of the study area that may I

be a reflection of water in this recharge area being influenced by the removal of C02 from ‘. a.

 

solution enhancing the aggressiveness of the water in dissolving solids, such as calcite
(Domineco and Schwartz, 1990). Calcite SI values in and around Saginaw Bay Area are
undersaturated with respect to calcite. This may indicate the mixing of two fluids as the
mixing of two solutions at equilibrium with calcite can result in a solution undersaturated
or supersaturated with respect to calcite (Langmuir, 1971). This is due to the non-linear
relationship between the concentration of Ca and the partial pressure of C02 in

equilibrium with calcite (Drever, 1988). Also the Saginaw Bay Area may be lacking in

74

 

............

 

b r — a . . — .

80‘”

 

 

 

55595

Figure 33. Frequency histogram for calcite saturation index values

 

 

r v‘fiw Ij'fiv—I l

 

Aragonite

 

 

 

for ground water from the Grand River-Saginaw aquifer.
, . . .

>325on

for ground water from the Grand River-Saginaw aquifer.

Figure 34. Frequency histogram for aragonite saturation index values

75

 

 

 

 

Dolomite

tF _ _ _

 

 

80-

_
o
6

0
4

5:268“

20-
0

ground water from the Grand River-Saginaw aquifer.

Figure 35. Frequency histogram of dolomite saturation index values for

76

carbonate material and therefore carbonate equilibrium is not a control in the Saginaw Bay
Area (Long et al., 1988). The average SI of dolomite and aragonite of -.9014 and -.0993
respectively suggest that waters are slightly undersaturated with respect to these minerals
throughout the aquifer. No major trend in SI distribution is noted with either dolomite or
aragonite within the study area, a fairly consistent distribution of data is observed. Similar
SI values for calcite, aragonite and dolomite are noted in the Glacial-drift aquifer in the

southern and fringe areas of the aquifer.

Evaporite minerals

Figures 36, 37 and 38 show distribution of 81s for halite, gypsum, and anhydrite from
Pennsylvanian waters. Waters are undersaturated with respect to halite and gypsum
throughout the study area. The average SI of gypsum is -1.6718, and halite with an
average SI of -6.23 00 appears to be highly undersaturated with respect to halite.

Alumino-Silicate and Silicate minerals

The controls on the solubility of Si and A1 are more difficult to address than carbonate
or evaporite minerals. In this study Si was studied directly fi'om modeling output,
however Al was studied though indirect ways.

Figures 39 and 40 presents frequency histograms portraying the distribution of quartz
and chalcedony $13. The average quartz SI of .3835 suggests waters are slightly
supersaturated with respect to the mineral. Chalcedony SI average value of -.0970
indicates near equilibrium for most waters. Consistent trends of $18 for quartz and
chalcedony are noted throughout the study area.

The technique most relied upon for an easy portrayal of stability relations between

silicates and aqueous solutions are on activity-activity or mineral stability diagrams

77

 

 

IAP/Kt

 

 

 

Figure 36. Frequency histopam of halite saturation index values for
pound water from the Grand River-Saginaw aquifer.

78

 

 

 

 

 

5:268“

Figure 37. Frequency histogram for gypsum saturation index values

 

 

for ground water from the Grand River-Saginaw aquifer.
l ' ' ' I I v . l v v . l

 

<.<._....__..._..17 4444444

 

 

 

zoneswoh

for pound water from the Grand River-Saginaw aquifer.

Figure 38. Frequency histogram for anhydrite saturation index values

79

 

 

1.5

 

 

 

55:95

1

IAP/Kt

Figure 39. Frequency histopam for quartz saturation index values

 

 

     

   

I fir

  

 

 

.....................

\\\\\\\\\\\\\\\ .
SS§§§§§ .
‘ S\\\\\\\\\\\\\\\\\ .

A l r . r r l A . l
-0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4

Chalcedony

 

 

for pound water from the Grand River-Saginaw aquifer.

5:25on

-1

IAP/Kt

Figure 40. Frequency histogram for chalcedony saturation index values

for pound water from the Grand River-Saginaw aquifer.

8O

(Garrels and Christ, 1965). These diagrams are based on activities calculated with
chemical modeling and on thermodynamic stability fields. This graphical technique uses
the assumption that all of the Al in the system is retained in solid phases, an assumption
that should be valid based on the low solubility of Al minerals (Long et al., 1986). Based
on this assumption the stability fields of Al bearing minerals can be described in terms of
the activities of the other dissolved species of the rock/water system (Long et al., 1986). ~._
Using the results of the chemical modeling on the ground water data an activity-activity
diagram was created for Na-aluminosilicate minerals presented as Figure 41. The mineral
stability presented on Figure 41 are based on Drever (1988). The ground-water sample
data plot within the kaolinite stability field. This indicates the potential for equilibrium of
the ground water with respect to kaolinite.
Using the results of the chemical modeling on the ground water data an activity-activity
diagram of K-aluminosilicate minerals is presented on Figure 42. The stability fields in the
diagram are taken from Drever (1988). The ground water data plot within the kaolinite

and muscovite fields.

SUMMARY

The results from WATEQ4F modeling indicate water-rock interaction is impacting the

solute concentrations of water from the Grand River-Saginaw aquifer. The magnitude of

 

rock-water interaction afl‘ecting ground water chemistry is difficult to quantify however
within the Grand River-Saginaw aquifer it is believed to be minimal as 815 are at or close
to equilibrium with respect to calcite as well as quartz and chalcedony. The impact of
water-rock interactions affecting solute concentrations of more concentrated water in the
system is small, as shown earlier the magnitude of solutes for these waters are derived
through mixing with brine. The more dilute waters in the system especially in the southern

part of the aquifer water-rock interactions are believed to be the dominant control on the

81

 

—-d_u—u—uqd——-—du-‘——-—-_—.*ul—r

 

 

.l l

 

 

1—-___—..rp—-———.[-—____—_.__—

9876543

.Eaa eon

 

-2

-3
LOG [H 4 8104 ]

Figure 41. Mineral stability diagram of sodium

-4

-5

ahrminoa'licate minerals.

 

 

u-u— a..— -—-u —_—— —u—— 14
_ _ _ _ _ _

.l

 

 

r 4

 

 

-—-~—__-__——..___~_-__-_-—

6543210

Ev: wou—

 

-3

LOG {H4 SiO ]

Figure 42. Mineral stability diagram dpotasn'mn
ahrminoailieate minerals.

-4

-5

82

chemical character of ground water in the Grand River-Saginaw aquifer. However active
rock-water interaction is not likely to be occurring in the aquifer as shown by Wood
(1969). This leads to the interpretation that the source of solute concentrations observed
in the more dilute waters in the system are derived through rock-water interaction that has
occurred in the overlying glacial-drift deposits prior to recharge into the bedrock aquifers.
This is in accordance with similar SI values, facies and dissolved solids distributions
observed in the Glacial-Drift aquifer waters (Wahrer personal commun., 1992). This
points to the importance of infiltrating water from the Glacial drift aquifer as a source of

solutes for less concentrated waters in the Pennsylvanian aquifers.

 

CHAPTER 5: ISQTOPE DATA REDUCTION AND RESULTS

INTRODUCTION

Isotopic compositions of elements having low atomic numbers are variable due to
isotopic fi'actionation in the course of certain chemical and physical processes occurring in
nature. Fractionation is due to variations in physical and chemical properties of the
isotopes (F aure, 1986). Some of the most important elements in which variations of
isotopic composition have been noted are hydrogen, oxygen, sulfur and carbon. The use
of stable isotopes of H, O, S and C in ground water studies has been widespread (Clayton
et al., 1966) (Graf et al., 1966) (Hitchon, 1969) (Desauliniers, 1981) (Siegel and Mandle,
1984) (Bradbury, 1984) (Long, et al., 1988) (Plummer at al., 1990) and (Long et al.,
1993). Ground water studies related to these elements specifically involve D and 18O,
13C and 34S (Domenico and Schwartz, 1990). The stable isotope ratios of O, H, S, and
C were measured in selected goundwater samples fiom the Grand River-Saginaw Aquifers
as a part of the RASA project (Dannemiller and Baltusis, 1990) (RASA, 1992) and Bay
County Project (Long et al., 1986). Only H and O stable isotope data exist for the Parma-
Bayport aquifer (Dannemiller and Baltusis, 1990). These data will be used to determine
the evolution of ground water chemistry, detect the presence of different ground water
masses, the mixing relationships between ground water masses, and the impact of
microbiological processes on water chemistry. Analyzing the isotopic composition of
water masses provides an independent check on controls on water chemistry as previously
discussed fi'om interpretation of chemical data. The best model for the geochemistry of an
aquifer is obtained when the results of isotopic analysis are combined with the results from

the chemical data reduction techniques (Long et al., 1986).

83

 

84

OXYGEN AND DEUTERIUM ISOTOPES

Oxygen and Deuterium isotopes are useful in the identification of water masses, mixing
relations between water masses and potential relative ages of water masses. The isotopic
composition of O and D is reported in terms of the difference of the 18O/160 and 2H/lH
ratios relative to a standard called SMOW (Standard Mean Ocean Water). The isotope

ratio is reported as a 6180 and 8D value, where the 8 values are expressed as a per mil

(%o) deviation from SMOW:

5=le-Rstdl/Rstd*103

where Rx is the isotopic ratio in the samples and Rstd is the isotopic ratio in the standard.
Negative 8 values correspond to samples relatively depleted (i.e. light) in the heavy
isotope species relative to the standard (F aure, 1986). Because the difl‘erences between
the standard and the sample are often small the 8 value is multiplied by 1000.

Figure 43 shows 8D and 5180 relations for ground water fi'om the Pennsylvanian
aquifers. These data are compared to the global meteoric water line of Craig (1961) and a
local meteoric water line fi'om Simcoe, Ontario, Canada (Desauliniers et al., 1981). The
Sirncoe data were collected precipitation approximately 120 miles east of the study area.
The equation for the Craig line is SD = 8*5180 + 10 and that of the Sirncoe line is SD =
7.516180 + 12.6. The distribution of data is in close agreement with both the Craig and
Simcoe meteoric water lines indicating the water is of meteoric origin, that is water is
assumed to have originated from the atmosphere and is unaffected by other isotopic
processes. Figure 43 also shows a wide range of isotopic signatures of meteoric water

exists in the Pennsylvanian aquifer. This large range does not reflect seasonal isotopic

85

 

    
 
 
  

l“"l""l'jj'l"'Tl
0..
_ MODERN METEORIC
WATER
-30-
'SIMCOELINE

 

Tr ' '1
ISMow-

 

 

1 .‘._.
2°; -60 -8D=7.5‘8 0+12.6 \ / >-
E - .
Q
to -90 — .. _
A \ GLOBAL METEORIC
WATER LINE
aD-8.o—s“o+1o.o
-120 — -
A ‘ GLACIAL—AGE A
‘ METEORIC GRAND RIVER-SAGINAWSAMPLB -
450-. . . . . WATER. . . . ,'.".““.“"?“f’°f”““. ."f
-2o -15 -10 -5 o 5

18
8 O (o/oo)

Figure 43. 8D versus 8180 for pound water from Grand River-
Saginaw and Patina-Bayport aqiufers.

A... 25,

 

86

variability in recharge water because ground water typically homogenizes this variability
into a yearly average (Lloyd and Heathcote, 1985), (Long, et al., 1988). Isotopic
signatures ofSD and 5130 range from -53.5 %o and -7.85 %o to -131.5 %o and -18.19 %o
respectively. The heaviest (least negative values) isotopic signatures observed, ranging
fiom around -8.00 %o to -12.00 %o are interpreted to represent modern meteoric ground
water in the aquifers. The heaviest signatures will be referred to as modern (post glacial)
meteoric water. Isotopically light signatures (< -l6.0 %o), found in ground water in the
Pennsylvanian units, as low as -18.19 960, are significantly lighter than expected from
modern recharge. Thus the very light values are anomalous and indicate that pound
water recharged the system when the climate was cooler. This interpretation is similar to
findings of other investigators who have discovered very light 8180 values in pound
water (Desauliniers et al., 1981) (Siegel and Mandle, 1984) (Bradbury, 1984) and (Long
et al, 1988). For example, Desauliniers suggests that ground water in glacial clays of the
Erie lowland in southwestern Ontario originated from a cooler climate and is a mixture of
late Pleistocene and modem ground water. 5180 values as light as -17 %o were found and
14C dates on water with light isotope signatures showed an age of >8,000 years before
present. Long et al., (1988) on the basis of Desauliniers work concluded that pound
water in Bay county in the eastern portion of the Saginaw Bay Area to be >8,000 years
old. This would suggest that during periods of glacial ice advances in Michigan pound
water recharge by glacial meltwater, depleted in 180, would have occurred in the basin.
This water is referred to as glacial meteoric water.

Distribution on Figure 43 indicates that modern and glacial meteoric water have mixed
causing a continuum of plotted values to be present. Interpretation of the data distribution
on Figure 43 indicates three water masses are present: (1) modern meteoric water (-8.00
%o to -12.00 %o) (2) glacial age meteoric water (< -16.0 96o) and (3) mixture of glacial age

meteoric and modern meteoric water (-12.10 %o to -15.90 96o) . Unfortunately, isotope

 

87

data for Parma-Bayport brine does not exist, therefore a fourth water mass known to exist
in the system is not represented on Figure 43.

Analysis of the areal distribution of 8130 in Figure 44 reveals an interesting pattern of
data exists. 8D signatures have the same general trends as 5180 and therefore a
distribution map of 8D is not included. The distribution of518o shows a pattern of
decreasing values fi'om > -10.00 %o in the south and west-central regions to values < -
16.00 96o present in the Saginaw Bay Area. This distribution follows data distribution of
Figure 43 that indicated mixing occurring between modern meteoric water (mostly in the
south and central part of the aquifer) and glacial age meteoric water (found exclusively in
the Saginaw Bay Area). The existence of thick relatively impermeable deposits mapped as l
lake sediments in the Saginaw Bay Area may be limiting the vertical movement of modern
recharge in the area preventing mixing with isotopically light water (Farrand and Bell,
1984). Along with the region being identified as a regional discharge location these
waters are able to retain the isotopically light signature due to slow flushing of the system
inhibited by overlying relatively impermeable sediments (Long et al., 1988) (Mandle and
Westjohn, 1989). The southern region of the study area is dominated by water with
modern meteoric signatures, this is in agreement with a hypothesized recharge area for the
aquifer based on previous discussion of hydrochemical facies, and dissolved solids
concentration distribution maps (Figures 12 and 16).

The mixing relationship described between modern meteoric and glacial age meteoric

 

does not represent the only mixing proposed to be taking place in the system. Previous
interpretations of elemental constituent plots (Figures 19 to 31) indicate meteoric water
mixing to some degree with brine as a source for solutes for much of the water in the
Grand River-Saginaw aquifer. Specifically, it is interesting to reference the distribution of
dissolved-solids and Cl on Figures 12 and 13 that show some of the more concentrated
waters in the system coincide with the distribution of isotopically light ground water in the

Saginaw Bay Area. Further the source of Cl and dissolved-solids can be attributed to

43

42—

 

88

< -l6.0

m > -16.0to < .14.0
I - > -l4.0to < -12.0
- > -12.0to < -10.o
u > -10.0

 

    

 

v. ’0‘ 9.3 tr
0‘ p,

 

Bue flan U.S. Geological
Survey l:500,000map

o 10 an an no 9"
ro 0 narrow“
Figure-14. 5“0distrirmtiourorgrmdwrtemmpredrromaroomd

89

mixing with brine from previous discussion. A question develops concerning the
relationship between brine and glacial-age meteoric water in the system, providing solutes
to the isotopically light water. In order to explain the scenario proposed by the isotope
data and chemical data a three end-member mixing relationship between modern meteoric

water, glacial-meteoric water and brine must exist.

Mixing of water masses

Figure 45 is a plot of 5180 versus Cl for pound water in the Pennsylvanian aquifers.
The data distribution indicates at low Cl concentrations (<100 mg/L) 5180 values are
between - 10.0 and -8.0 %o. As Cl concentrations increase (>200 mg/L) 8180 values
exhibit a variety of signatures from - 18.0 to - 8.0 %o. Chloride concentrations as high as
5,000 to 7,000 mg/L have associated isotopic values as low as -18.0 %o. The most
concentrated samples represented on the plot with Cl concentrations > 10,000 mg/L are
associated with the most isotopically heavy water sampled fiom the Pennsylvanian
aquifers. Interpreting this plot to explain a mixing relationship between water masses that
can explain both the chemical data and isotopic data is difficult as no data from the Parma-
Bayport brine end-member exists.

In order to better investigate this mixing problem it is necessary to focus on a study by
Long et al., (1993). Long et al., (1993) performed a study encompassing all waters within
the RASA study and were able to define the mixing relationship between brine, modern
meteoric and glacial meteoric water based on the premise that only a small amount of the
Cl content of a brine would be required to produce the observed CI content in the mixed
waters and therefore not having a great impact on the isotopic signature. Using data fiom
the Glacial Drift aquifer as well as the Grand River-Saginaw, Parma-Bayport, and
Marshall aquifers a 8180 versus Cl diagram was created (Figure 46). Isotope data from
Marshall brine is the only available brine end-member data (Clayton et al., 1966). Due to

 

3180

 

90
l T I I I I I I T I I I I I I I I I I I 17
r- . A -
L s
_ m A A __
gears AA 4A.
r- A a A 1% A A A M
b— & AA A —t
r A A A A A r
A AA
)— —-t
A A a
L- % -t
r- A e
r. A% ..
8 AA AA
)— AA& -1
F- A d
A A A
A A
” 2%“ ° ‘
r- A AA
A AA l
A A ..
F A
+- A A 7
A
r—- A —r
A
>— A A A —r
I A A A Ohm-Bayport ‘

 

 

 

2 3
LOG C1 (mg/L)

Figure 45. 5180 versus Cl for pound water from Grand River-

Saginaw and Parma-Bayport aquifers.

III-.- .-rh -A-l-

91

 

 

 

 

    
  

 

 

IIIHI'H'I'H'I'H'I l'r‘l 'I
5F MIXINGLINES j
;A:818o=-8.0o/oo ?
0; 13:8180= -10.0o/oo _
.c:518o = -20.0 o/oo
-5:— _
-10:r B:
-15:‘ 1
i mesa?
'20_1.r.11....1....1....1....irrrr(i9?6)rr.|_
-1 O 1 2 3 4 5 6

LOG C1 (mg/L)

Figure 46. 81% versus Cl for pound waters sampled from the
Glacial-Drift, Grand River-Saginaw, Parma-Bayport and
Marshall aquifers (Modified from Long et al., 1993).

92

chemical similarities previously shown between the Patina-Bayport brine and brine in the
Marshall Formation an assumption is made for this thesis that the two brines are also
isotopically similar. With this assumption the same method of Long et al., (1993) can be
applied specifically to the Pennsylvanian waters.

Figure 46 is a plot of 8180 versus Cl concentration of groundwater samples from the
entire RASA study in an efi‘ort to link mixing relations observed from chemical data
(Figures 19 to 31) with that of isotope data (Figure 43). Long et al., (1993) investigated
mixing on the isotopic signature of water, a fresh water and a brine were theoretically
mixed in various proportions and the resultant 5180 values and Cl concentrations were
calculated. The fresh water end-member was assigned a Cl concentration of 1.00 mg/L
and three isotopic signatures -8.00 %o, the heaviest modern meteoric water, -10.00 %o, the
average modern meteoric water, and -20.00 %o, isotopically light glacial age meteoric
water. The brine end-member was assigned a Cl concentration of 200,000 mg/L and a 5
18O signature of 0 %o, based on data from Clayton et al., (1966). Chloride concentrations
were calculated by weight averaging the end-members and the 5130 value of the mixed

waters was calculated using the following equations:

5180mm: = F * X*518013R1NE + (X - 1) * 5180msrr

CIMIX'rURE = X * CIBRINE + (X - 1) * CIMETEORIC

Where F is the ratio of the water weight in brine to the weight in pure water and X is the
fi'action of brine mixed. A value of .70 was used for F in the calculations (\Vllson and
Long, 1993). Results of calculations on Figure 46 show all data fall within a mixing
envelope defined by -8.00 %o, -1000 %o, and -2000 %o 5130 values. It is interesting to
note the 8180 values of the mixtures remain relatively constant over the range of most of

the data. The 8180 values do not change significantly in the mixtures until Cl

 

93

concentrations exceed 10,000 mg/L that can be simulated if the fresh water end-member
mixed with 5% brine. Therefore, Long et al., (1993) showed mixing fresh water (recent
and glacial) with various amounts of brine can account for the observed Cl and 5180
values of groundwater in the study area. This same mechanism is believed to be operating
in the Pennsylvanian bedrock system as mixing with brine in the Parma-Bayport as the
source of solutes for the more concentrated samples in the Grand River-Saginaw aquifer.
Therefore it is hypothesized that mixing of Parma-Bayport brine with modern meteoric
and glacial meteoric waters from the Grand River-Saginaw is providing the solute
concentrations observed, without impacting 8180 signatures of the glacial meteoric water
as shown by Long et al., (1993). Without isotope data fi'om the Parma-Bayport brine a

more definitive conclusion is prohibited.

Summgg

Analysis of 51 8O and 8D from Pennsylvanian waters indicate three water masses are
present; (1) modern meteoric (post-glacial) and (2) glacial age meteoric a third water mass
exists in the Pennsylvanian bedrock sequence, the Parma-Bayport brine which is not
represented due to lack of isotope data. Modern meteoric values are mainly found in the
south and periphery of the basin and glacial age water is restricted to a portion Saginaw
Bay Area with mixed water present separating the modern and glacial waters. A model
can be formulated to explain mixing with a brine as a source of solutes while preserving
the isotopically light signatures. This is most usefirl in correlating the chemical data and
isotope data of isotopically light waters with high Cl concentrations in the Saginaw Bay
Area. This model may be used to explain the mixing between Parma-Bayport brine and

Grand River-Saginaw waters and explain solute and solvent geochemistry.

 

94

SULFUR AND CARBON ISOTOPES

The stable isotopes of C and S are typically used in carbonate and sulfate-sulfide
systems. These systems are very complex in the subsurface and C and S isotopes are used

best at process identification (Donrineco and Schwartz, 1990)

Sulfur Igtopes

Sulfilr isotopes signatures can be used to identify the processes contributing to the
evolution of S chemistry. In pound water sulfate may be derived fi'om dissolution of
calcium-sulfates and through the oxidation of iron-sulfides. Specifically, the ratio of 34S
to 32S is of concern in sulfur isotope studies. The isotopic composition is expressed in

terms of 5348 that is defined as: (Bowen, 1988)

834s = [Rx - Rstd] letd * 103

where Rx is the isotopic ratio in the samples and Rstd is the isotopic ratio in the standard.
Negative 8 values correspond to samples relatively depleted (i.e. light) in the heavy
isotope species relative to the standard (F aure, 1986). The standard is the S in troilite
(FeS) of the iron meteorite Canyon Diablo whose 328/348 ratio is 22.22 %o.

 

Dissolution of solids containing S in a pound water system can change the 534$ value
or $04 concentration of pound water depending upon the source of sulfate, i.e., gypsum,
organic matter (peat or coal), or from oxidation of sulfide minerals such as pyrite or
possibly a combination of all of these (Domenico and Schwartz, 1990). An important
fiactionation reaction involving 8 that operates in ground water systems is sulfate

reduction that takes the general form:

95

2 H+ 504 +2 [CHZO] = 2 H20 +st + C02

The result of this process is depletion in sulfate concentrations and enrichment in 8348

value. The isotopic fractionation associated with this reaction appears to be due to the

bond strength with 34S forming stronger bonds than 328 (Long et al., 1986). The degree
to which fiactionation occurs is a function of the temperature, availability of nutrients, pH,

type of organic material utilized, and type of bacteria present (Kaplan, 1983). In inorganic

systems however, the extent of isotopic fractionation that occurs is due to difi‘erent rates
at which S-O bonds are broken (Faure, 1986).

The bacteria identified to be of primary importance in the reduction of sulfate is
Desulfovibn'o desulfirricans an anaerobic bacteria which splits oxygen fiom sulfate and
excretes H2S that is enriched in 328 relative to sulfate, and the sulfate in pore water
becomes isotopically heavier. Therefore the expected trend for sulfate reduction is
decreasing sulfate concentrations accompanied by increasing 834s values.

Long et al., (1986), performed a study on groundwater in Bay County, MI. fi'om the
Glacial Drift and Grand River-Saginaw aquifers. Through the use of C and S isotopes
they were able to delineate sources of sulfate for groundwater samples analyzed. Control
on sulfate concentrations could not be entirely linked to only the dissolution of gypsum
and oxidation of pyrite. Another control on sulfate concentrations mainly a biochemical
process was indicated. Long concluded based on analysis of S as well as C isotopic
signatures that sulfate reduction was occurring in aquifers in Bay County.

Data used in this thesis are from RASA sampling from 1986-88 (Dannemiller and
Baltusis, 1990) and 1991 (WATSTORE, 1992) which include 18 S isotopic analyses and

data from Long et al., (1986) adding 14 S analyses. Figure 47 is a frequency histogram of

S isotopic data from the Grand River-Saginaw aquifer. Values range from -2.9 %o to
67.44 %o with an average of 21.04 %o. Most data fall within a 12 %o to 32 %o range,

however due to only 32 samples available the distribution of data may not actually reflect

 

Marine Evaporites

 

12_ "

 

V

l
l

10}

 

14—]‘4 J_LJ l I l

\ _;

frequency
/ ///////////////////////////%1 i

 

 

 

//////////////////////////l

 

 

 

 

: Sulfide in Pennsylvanian :
4 j rocks in Michigan basin j
2} —

- ‘ ‘ -
0; § Q\ g _

-10 O 10 20 3O 40 50 60 70

34
8 S

Figure 47. Frequency histopam for 5343 in dissolved sulfates for
pound water from the Grand River-Saginaw aquifer. Ranges shown

represent S values for marine evaporites (Anderson and Arthur, 1983)
and sulfide in Pennsylvanian rocks in the Michigan basin.

A“?

 

 

97

true sulfur isotope distribution in groundwaters throughout the Grand River-Saginaw
aquifer.

Sources of sulfate to waters in the Grand River-Saginaw aquifer have been stated as
being from dissolution of gypsum and oxidation of iron sulfides (Long et al., 1986),
(Wood, 1969). These minerals will have difl‘erent 5348 signatures, therefore the signature
of groundwater could reflect the source of sulfate. One problem exists in that the 534$
values for gypsum do not exist for this system and therefore must be estimated. 834s
values for pyrite in the Pennsylvanian units of the Michigan basin range from 9.6 to 29.3
and a values for ancient sulfates in marine-evaporites have signatures from 8 to 35 %o with
Pennsylvanian age sulfates ranging from 15 to 22 %o (Anderson and Arthur, 1983)
Isotope data available on Figure 47 show 2 samples are < 10 %o and l is greater than 45
%o. Nearly all data fall within the isotopic signature of associated with gypsum and pyrite
making it dificult to differentiate a single source of sulfate. Few samples plot outside the
ranges used for pyrite and gypsum leading to the interpretation that bacterial processes are
causing the high S isotope values observed. To further investigate this 534$ is plotted
versus sulfate for Grand River-Saginaw waters.

Figure 48 plots 534$ versus sulfate concentration and shows higher sulfate
concentrations (> 300 mg/L) are associated with 834$ values < 20 %o and lower sulfate
concentrations (< 300 mg/L) are associated with 834$ values as high as 67.44 %o. The
depletion of sulfate as 634$ signature becomes heavier is what is expected if the
microbiological reduction of sulfate is occurring in the system (Long et al, 1986). The
distribution observed on Figure 48 shows some data form an increasing 534$ signature as
sulfate concentration decreases. Not all data, even some from Bay county, adhere to this
trend indicating sulfate reduction may be occurring albeit in isolated areas. This is
consistent with the conclusion of Long et al., (1988) as sulfate reduction was shown to be
taking place in various parts of the aquifer for different lengths of time, therefore

explaining uneven degrees of isotope enrichment and sulfate depletion present.

u

 

80

60

20

Figure 48. 8345 versus 804 for pound water from the Grand River-Saginaw

98

 

 

Grand River-Saginaw aquifer

 

 

A

A
A

A‘

A A
A9; A
A A

A AA AA A

A? AAAA
A
J l 1 l l 1 1 l l l l l l l l l #1

Log so 4(mg/L)

aquifer.

 

p}

99

Carbon Isotopes

The concentration of stable carbon isotopes in ground water is used to indicate the
origin and evolution of ground water and determine the source of dissolved inorganic
carbon (DIC) in an aquifer. Dissolved inorganic carbon species (112CO3, HCO3, C03,
and C02) are important components in ground water as they buffer pH, produce
alkalinity, complex other dissolved species and affect the solubility of many minerals

common in aquifers (Long et al, 1986). The isotopic composition is expressed in terms of

513C which is defined as:

513C = [Rx - Rstd] IRstd * 103

where Rx is the isotopic ratio in the samples and Rstd is the isotopic ratio in the standard.
Negative 5 values correspond to samples relatively depleted (i.e. light) in the heavy
isotope species relative to the standard (F aure, 1986). The carbon isotopic signature
obtained from a ground water sample is the result of exchange of ground water with
various sources of carbon (coal, C02 gas in soil zones, carbonate minerals, other carbon
bearing minerals, methane gas, and plant material) each of which has a distinct range of 8
13C values that is the basis of being able to differentiate sources of carbon in an aquifer.
Marine carbonates including aragonite, calcite, and dolomite commonly have 813C values

from -2.0 %o to +2.0 %o. Atmospheric C02 has values from-5.0 %o to -7.0 %o. Land

plants found in temperate and colder climates have 813C values from -30.0 %o to -20.0 %o.

It is important to note that DIC is likely to be the result of many carbon sources (Long et
al, 1986).

Carbon isotopes available for this thesis include 50 analyses obtained from Long et al,
(1986) and 43 analyses obtained from RASA sampling (Dannemiller and Baltusis, 1990),

All».—

 

 

100

(WATSTORE database, 1991). 513C values range from -21.36 %o to -6. 16 %o with an
average of -l3.34 %o (Figure 49). Long et al, (1988) indicated that organic matter was a
more important source for carbon than carbon derived from carbonate minerals in the Bay
county area. This was based on 57% of the 513C values were < -15.0 %o. A 513C value
of -1 5.0 %o is the lower limit generally expected for a mixed carbonate mineral-organic
source (Long et al., 1986). Sources for organic carbon in Bay county area could be from
lignite, organic-rich shales, and organic rich ”fire-clay" in many cases associated with coal.
Also Long et al, (1988) also found an uneven distribution of 513C values to be indicative
of microbiologic activity, principally sulfate reduction, however no direct relationship was
found between decreasing 813C values and increasing HCO3, a by-product of sulfate
reduction. This lead to the conclusion that sulfate reduction is occurring in Grand River-
Saginaw aquifer in Bay county, however it is heterogeneously distributed with some areas
having higher reduction rates than others.

Data located outside Bay county indicate that carbonate minerals may be having more
of an impact on the source of carbon combined with an organic source as values are
typically -15.0 %o to ~12.5 %o. This is shown by Thorstensen and Fisher, (1979), in which
a combined source of carbon consisting of lignitic material (-25.0 %o) and carbonate
minerals (0.0 %o) result in an actual average value of 513C in ground water of -12.1 %o.
This interpretation is consistent with the presence of coal deposits in the Saginaw
Formation (W anless and Shideler, 1975) and ubiquitous presence of carbonate cements in

the Grand River-Saginaw aquifer (D. Sibley personal commun., 1992).

 

 

 

101

 

 

 

 

I I I I I l I I I f T I T I I I I
80 -
" Grand River-Saginaw aquifer
” A
60 -
U) _
E 40 — a
A
0° _
' Al
_ A A
AAA 59
20 F— A A AA AAA A
_ A
O l l l 1 1 l 1 l l l l l 1 J_ L 1 _1
O 1 2 3

Log SO 4(mg/L)

Figure 48. 83% versus 804 for ground water from the Grand River-Saginaw

aquifer.

 

102

gummy !

Sulfur and carbon isotope data are more diflicult to interpret than oxygen and
deuterium as these need a systematic site-specific characterization of important reactions
in terms of sources and sinks of carbon and sulfur. The scale of this thesis does not allow
this interpretation and lack of important S and C source solid-phase information precludes
anything more than speculation of sources of S and C from limited isotope database
available.

In accordance with the work of Long, et al, 1986 sulfate reduction is occurring in
portions of the Saginaw Bay Area, however many samples show no evidence of it
occurring in the rest of the system. Sulfur isotope data show the influence of gypsum
dissolution and pyrite oxidation as a source of sulfate to the system, although it is not
possible to difl‘erentiate which has a greater impact on sulfate concentrations. The impact
of mixing with brine cannot be overlooked in analyzing the sulfirr isotope data. Addition
of sulfate to the system from a brine source has also been shown to be important and is to
be considered as a more significant source than dissolution of gypsum and oxidation of
pyrite.

In the Bay county area organic matter appears to be a more important source of carbon
than carbon from carbonate minerals. Also, consistent with sulfur isotope data sulfate
reduction is occurring albeit heterogeneously distributed throughout the Bay county
region. Carbon isotope data from outside Bay county indicate the source of carbon is

equally impacted by carbon from organic matter and carbon from carbonate minerals.

CHAPTER 6: SUNIMARY AND CONCLUSION:

SUMMARY

The geochemical distribution maps indicate high concentrations of dissolved solids and
chloride exist in the central part of the aquifer and in the Saginaw Bay Area. Low
concentrations are mainly found in the south and southeastern parts of the aquifer
consistent with areas designated as recharge areas to the aquifer. The low dissolved solids
concentrations show a similar distribution to those found in water sampled from the
overlying glacial drifi aquifer. Low concentrations of sulfate exist in the Saginaw Bay
Area and high concentrations are present where the aquifer is overlain by or near Jurassic
deposits. Piper plots show a linear trend on the cation ternary diagram between dilute Ca-
rich water (< 750 mg/L) and more concentrated (>2,000 mg/L) Na-rich water end-
members with a mixing trend separating them. Water in the anion ternary plot between
HCO3 4» CO3 - SO4 dominant at low dissolved solids, among HCO3 + C03 - Cl - 804
dominant at intermediate dissolved solids and Cl - 804 dominant at high dissolved solids.
Distributions on anion ternary diagrams show more concentrated waters in each interval
plotting closer to the SO4-Cl dominant area. The change in the distribution pattern of the
data in the diamond area as a function of increasing dissolved solids reflects those changes
in the cation and anion ternary diagrams. The pattern changes in the ternary and diamond
diagrams are consistent with the hypothesis in which water masses with various
compositions are mixing. Main hydrochemical facies in the Pennsylvanian aquifers are Ca-
HCO3, Na—Cl, and Ca-SO4. With Ca-HCO3 facies predominantly in the south and Na-Cl
facies mainly in the east-central part of the aquifer.

Analysis of Cl/Br ratios provide evidence that waters in the Pennsylvanian aquifers are
genetically related to formation brine and the source of Cl is not related to halite

dissolution.

103

 

'1
. . ‘ngs A...

T.mmliilnn—'—r
. ’ . . A.
“—m. .
n-

104

Brine in the Michigan basin Traverse Group and Marshall aquifer is proposed to have
formed from the evapo-concentration of seawater. Brine in the Parma-Bayport was
hypothesized to have formed through the same process therefore chemical analyses were
compared to evaporation of seawater trajectories according to the method proposed by
Carpenter, (1978). Chloridezbromide and sodiumzchloride diagrams allowed the
preliminary interpretation that the Parma-Bayport brine had originated from evapo-
concentrated seawater and that solutes of less concentrated saline water in the Grand
River-Saginaw aquifer plotted along a dilution trend from brine concentration. This
relationship show a link between brine and other concentrated waters in the system.
Interpretation of ion:Br and ion:Cl diagrams showed the Grand River-Saginaw aquifers
saline water as being genetically related to Farina-Bayport brine as well as further
indicating the similarity of the Parma-Bayport brine and Marshall brine and Traverse
Group brine. The Parma-Bayport brine showed diagenetic alterations from
dolomitization, some degree of sulfate reduction and possibly alumino-silicate reactions.

The dilute water end-member (< 750 mg/L), located mostly in the southern and
southeastern parts of the aquifer, can be explained through rock-water interaction
occurring in the glacial drift deposits causing the concentrations observed. Minor mixing
with brine is also believed to serve as an additional albeit minor source of solutes.
Geochemical modeling shows that a source of solutes derived from rock-water interaction
taking place in the Grand River-Saginaw aquifer is likely. Solutes of less concentrated
waters of the Grand River-Saginaw aquifer are derived mostly through rock water
interaction occurring as the water moves through the overlying glacial drift aquifer and
eventually recharges the Grand River-Saginaw aquifer. In these areas where less
concentrated waters are present, dissolved solids concentrations and hydrochemical facies
distributions mimic those found in the overlying Glacial-Drift aquifer supporting this
conclusion. The chemical similarity between water in the Grand River-Saginaw and

Glacial-Drift aquifers especially in the southern part of the aquifer is in accordance with a

 

105

hydraulic potential for water to move from the drift to the Grand River-Saginaw aquifer in
the southern portion of the aquifer (Wood, 1969).

Stable isotopes of O and D indicate three meteoric water masses are present in the
aquifer: (1) modern meteoric water, (2) glacial age meteoric with a third water mass, the
Patina-Bayport brine not represented by O and D data on the diagram. A mixing model
was applied to explain high solute concentrations (>3,000 mg/L dissolved-solids)
associated with water with a glacial meteoric water signature based on requiring only a
small percentage of brine to cause solute concentrations observed without and having no
efi‘ect on the isotopic signature of the water sample. This model links mixing
interpretations made independently from analysis of chemical and isotope data. The model
explains mixing relationships between brine, modern meteoric water and glacial meteoric
water causing solute concentrations and isotopic signatures for the majority of samples.

Stable isotopes of C and S indicate, in accordance with Long et al., (1988), that sulfate
reduction is occurring in the Saginaw Bay Area. The source of sulfate could not be
unequivocally decided based on sulfur isotopic signatures. Gypsum dissolution and pyrite
oxidation are implicated as sources of sulfate, however lack of data for the aquifer (32
samples) and the overriding importance of brine, previously pointed out, as a source of
solutes for Grand River-Saginaw water must be considered in the interpretation of sulfirr
isotope data. Carbon isotope data also supported the interpretation of Long et al., (1988)
that sulfate reduction was occurring in Saginaw Bay Area. Sources of carbon in the
aquifer system also could not be concluded with organic carbon and carbon from

carbonate minerals as important sources.

 

 

. imam. . .... .-
4 l I

 

 

106

CONCLUSIONS

1) Three water masses are identified in the Pennsylvanian aquifers:
(1) Modern meteoric water
(2) Glacial meteoric water

(3) Farina-Bayport brine

2) Water chemistry in the southern part of the Grand River-Saginaw aquifer is mainly
controlled by recharge water which acquires solutes through rock-water interaction that
occurs in the overlying Glacial-Drift deposits. In parts shale membrane filtration (reverse
osmosis) may be occurring causing the lower dissolved-solids concentrations in the Grand
River-Saginaw aquifer than in overlying Glacial-Drifi aquifer.

3) Ground water with higher dissolved solids concentrations in the Grand River-Saginaw
aquifer, particularly in the east-central part of the study area, are mostly influenced by
mixing with brine in the Parma-Bayport aquifer. Mixing is occurring closer to Saginaw
Bay as this area is identified as a regional discharge area for the aquifer system. The
mixing relationships between all water masses does exist and is identified in the
Pennsylvanian aquifers through linking isotope and chemical data by analogy to Long et
al., (1993).

4) The origin of the Parma-Bayport brine can be implied even with limited data available.
It appears that the origin of brine in the Parma-Bayport aquifer is from evaporative
concentrated seawater just short of halite saturation and the brine has been impacted by
aluminosilicate reactions causing K depletion, some degree of dolomitization affecting Ca
and Mg concentrations, and sulfate reduction lowering sulfate concentrations, and possibly
impacted by gypsum dissolution. Without more data from the aquifer a definitive origin of

the brine cannot be reached. Data from brine in the Parma-Bayport was found to be

 

 

 

107

hydraulic potential for water to move fi'om the drift to the Grand River-Saginaw aquifer in
the southern portion of the aquifer (Wood, 1969).

Stable isotopes of O and D indicate three meteoric water masses are present in the
aquifer: (1) modern meteoric water, (2) glacial age meteoric with a third water mass, the
Parrna-Bayport brine not represented by O and D data on the diagram. A mixing model
was applied to explain high solute concentrations (>3,000 mg/L dissolved-solids)
associated with water with a glacial meteoric water signature based on requiring only a
small percentage of brine to cause solute concentrations observed without and having no
efi‘ect on the isotopic signature of the water sample. This model links mixing
interpretations made independently from analysis of chemical and isotope data. The model
explains mixing relationships between brine, modern meteoric water and glacial meteoric
water causing solute concentrations and isotopic signatures for the majority of samples.

Stable isotopes of C and S indicate, in accordance with Long et al., (1988), that sulfate
reduction is occurring in the Saginaw Bay Area. The source of sulfate could not be
unequivocally decided based on sulfur isotopic signatures. Gypsum dissolution and pyrite
oxidation are implicated as sources of sulfate, however lack of data for the aquifer (32
samples) and the overriding importance of brine, previously pointed out, as a source of
solutes for Grand River-Saginaw water must be considered in the interpretation of sulfur
isotope data. Carbon isotope data also supported the interpretation of Long et al., (1988)
that sulfate reduction was occurring in Saginaw Bay Area. Sources of carbon in the
aquifer system also could not be concluded with organic carbon and carbon from

carbonate minerals as important sources.

 

‘9

 

THE BIBLIOGRAPHY

 

109

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